Psychological Medicine, 1977, 7, 613-618 Printed in Great Britain
Lithium therapy and alkaline earth metal metabolism: a biochemical screening study N. J. BIRCH, x A. A. GREENFIELD AND R. P. HULLIN From the Department of Biochemistry, University of Leeds, and the Computing and Statistics Section, British Iron and Steel Research Association, Sheffield
A study is described of 90 patients receiving lithium prophylactically for recurrent affective disorder. A total of 90 biochemical variables was analysed by correlation matrices. No abnormality in calcium or magnesium metabolism was detected though this may merely be a reflection of the insensitivity of the screening technique used.
SYNOPSIS
INTRODUCTION Theories of the mode of action of lithium salts in manic-depressive psychoses suggest that lithium interacts with either the alkali metals sodium and potassium or with the biogenic amines (Shaw, 1973). It has also been proposed that its mode of action might be due to the 'diagonal' relationship in the periodic table between lithium and the alkaline earth metals, magnesium and calcium (Birch, 1970, 1974 a; Frausto da Silva & Williams, 1976). Young rats, treated for periods of 28 days with lithium, have been reported to have a decreased concentration of calcium in bone (Birch & Jenner, 1973). The occurrence of a similar effect in mature humans during lithium therapy would represent a long-term side effect which requires investigation. Various effects of lithium on alkaline earth metal metabolism have been reported in the literature. Both decreased uptake of 48Ca, MMg and ^P by rat bone and increased phosphate uptake in rat diaphragm occur following lithium administration (Mellerup et al. 1970; Gotfredsen & Rafaelsen, 1970; Mellerup & Plenge, 1976). Other authors (Andreoli et al. 1972; Gotfredsen & Rafaelsen, 1970; Aronoff et al. 1971; Birch & Jenner, 1973) have also reported increased excretion of the alkaline earth metals following lithium treatment in man and in animals. The production of soft-shelled eggs in the domestic fowl given 1 Address for correspondence: DrN. J. Birch, Department of Biochemistry, University of Leeds, 9 Hyde Terrace, Leeds LS2 9LS.
lithium (Creek et al. 1971) has not been confirmed by Scott et al. (1973) with a lower dosage of lithium. Many of these findings arise from studies of relatively immature animals and might not apply to pre-existing bone, but evidence of pharmacological effects of lithium on calcified tissues in animals indicates the importance of such studies on human subjects receiving longterm lithium treatment. The accumulation of lithium in the bones of rats and adult human subjects (Birch & Hullin, 1972; Birch; 19746) also makes such investigations necessary. An attempt has therefore been made to investigate biochemical effects of lithium in a group of 90 out-patients receiving maintenance lithium therapy. This group, which had been receiving lithium for an average period of 3 years (range 0-5-9 years), visited our lithium clinic regularly for monitoring and thus the whole group could be seen over a relatively short period. Many members of this group had shown a marked prophylactic action of lithium against unipolar and bipolar affective illness (Hullin et al. 1975) and it was therefore essential to prevent patients refusing treatment because of long-term side effects which might not be established by this or subsequent investigations. To avoid alarming the patients, therefore, only the normal routine blood sample, and an additional spot urine sample were taken. The restricted information obtainable from a random urine sample was accepted as a price which had to be paid for a rapid screening test of any gross disturbance in electrolyte excretion. We appreciated the imprecision of the technique
613
614
N. J. Birch, A. A. Greenfield and R. P. Hullin
and thus had some expectations of failure to show significant conclusions. In the event the results showed that the technique of 'spot' urine sampling is capable of giving results which are internally consistent and also agree with other workers. This technique may be of value in other outpatient studies and in the case of uncooperative or incontinent patients; previously it has been reported as a valid technique for the screening of calcium excretion (Wills, 1969). Throughout this paper the following abbreviations will be used: M = male, F P r e = premenopausal female, F P o s t = postmenopausal female, Cx = clearance of x, Rx = clearance of x/clearance of creatinine, Ux = urine concentration of x, Px = plasma or serum concentration of x, Tx = excretion rate of x with respect to time. A preliminary report of part of this study has been previously presented (Birch et al. 1974). METHOD Out-patients attend the lithium clinic at intervals of 4^10 weeks depending on age, stability of standard lithium levels and psychiatric state. A blood sample is taken for the determination of serum lithium and the patient is interviewed. In this study, 25 ml of blood was taken from an antecubital vein, into a plain tube, and a urine sample obtained in a suitable container. The patients were informed that the urine sample was required for an investigation of electrolyte excretion during lithium therapy and all consented. Since the only difference from a normal visit was the provision of a sample of urine, the procedure was accepted as routine and unremarkable. To minimize diurnal and dietary variations, patients were only included in the series if their blood and urine specimens were collected between 09.00 and 12.00 hours. To avoid seasonal variations the samples were collected over an 8-week period in early summer. Lithium, sodium, potassium, magnesium, calcium, phosphate, chloride, creatinine and urea were determined in serum and urine, in all cases. Cations were determined by atomic absorption spectroscopy (Unicam SP90) using dilutents previously described (Birch & Jenner, 1973). Chloride was determined by EEL model 240 chloride meter. Phosphate, creatinine, urea and serum alkaline phosphatase were determined by methods described by Varley (1967).
At the interview the following data were obtained: weight, height, time since last intake of lithium, and time since last micturition. The latter information, based on patient's recollection, was used as an additional basis for excretion rates. During a subsequent visit, gynaecological and obstetric histories were obtained from female patients. Age, period on lithium and psychiatric history were obtained from records. The data were numerically coded and processed from this point with no further reference to named patients. Completed analyses and full information were obtained from 90 of 110 patients from whom samples were obtained and statistical analyses were carried out on this data set. The remaining subjects were excluded either because they were unable to produce a urine sample or because the serum obtained was insufficient for the determination of all the variables. Algebraic transformations were carried out to determine rates of excretion, with respect to time (Tx) and creatinine excretion (£/x/C/Creat). Clearance values (Cx) were calculated on the assumption that the determined plasma concentration was representative of the whole period of urine collection. The clearance fraction with respect to creatinine clearance was also calculated (CJ Ccreat = Rx). The dose was recalculated in terms of body weight and surface area, the latter from the formula of DuBois & DuBois (1916). The statistical analysis was carried out by correlation coefficients determined in various combinations of a 35 x 35 matrix using an IBM 1800 computer. A limited biochemical survey was also carried out to identify cases of Paget's Disease in the long-stay female wards of the psychiatric hospital, though none was found. The serum calciums, magnesiums, ureas and alkaline phosphatases as determined in the same laboratory contemporaneously with the present study, are reported as a non-matched control series to show that the results as determined were within the normal ranges for the laboratory and within accepted normal ranges. RESULTS The composition of the series (Table 1) was as expected for the known occurrence of this group of disorders (Schou, 1968). Females outnumber males by about two to one and there is a pre-
Biochemical screening in lithium prophylaxis
615
Table 1. Composition of patient series. Values are given as means + S.D.
Male Premenopausal female Postmenopausal female All female Combined male and female
No.
Age (years)
29 24 37 61 90
52-9±13-4 36-9±8-l 60-9±7-8 51-l±14-3 5l-7±13-94
Height (cm) 173-7+.8-3 162-9±6-2 156-4±7-4 159-1 ±7-6 163-8± 10-4
Weight (kg)
Surface area
77-3±12-4 64-8±150 66-l±10-2 65-5±12-3 69-3+.13-5
l-910±0-176 l-689±O18O l-659±O-143 l-671±0158 1-749+0199
Table 2. Mean ± S.D. values of variables in male, premenopausal and postmenopausal groups Male (N = 29) U. vol (ml) Period of specimen (h) Time since last Li dose (h) Time on Li (months) Dose Li (mg Li.CO,) Dose Li/kg body weight Dose Li/m$ body area
139-4±116-9 1-718± 1-185
3-982±4-18 30-25±26-76 813-7±199-5 10-76±2-962 427-7±1050
Premenopausal female (N = 24)
Postmenopausal female (N = 37)
1240± 118-6 2099±1199 4-260+.4-701 13-58±14-I3 7760+. 260-2 12-30±4-489 460-6± 154-6
1480± 124-6 2076±1029 6-90±7-89 3704±22-23 666-6± 178-8 10-27±3-108 4020± 106-4
Table 3. Urinary calcium I creatinine excretion ratio. Mean ± S.D. mgCa/mg creatinine (number of subjects in parentheses) Male
Premenopausal female
Postmenopausal female
Present Li series
0151±0120(29)
0172±0113(29)
0122±0061 (37)
Nordine/a/. (1967) Dauncey & Widdowson (1972)
O163±OO82(1O4) 0-15^-016(9)
dominance of postmenopausal females. The mean age and standard deviation of the total male and female groups is very similar. The mean age of the menopause for the post-menopausal female group elicited by interview was 44-6 ±9-4 years. Mean values of some of the variables in the male, premenopausal and postmenopausal female groups are given in Table 2. The smallest urine volume recorded was 25 ml. The agreement between excretion rate as obtained from the patient's report and from urine volume/creatinine ratio was surprisingly good. Correlations between the two measures were significant in the male and premenopausal females (P < 001), in the postmenopausal females (P < 0001), total females and total subjects. Thus, the patients appear to have reported their previous time of micturition with reasonable accuracy. No significant correlation was found between
0156±0069(88)
calcium excretion rate and serum lithium, lithium excretion rate, lithium dose however expressed, and period of lithium treatment. The calcium values determined were within the normal range. Serum alkaline phosphatase was within the normal limits given by Eastham(1971) (4-5-9-5 KingArmstrong Units/100 ml) in all except 12 subjects (M = 2, F P r e = 3, F P o s t = 7). Of these one F P r e was slightly below the range, but she and all except one .Fpost subject were within the range suggested by Baron (1970) (3-13 King-Armstrong Units). Table 3 shows the urinary Ca/creatinine ratios of the various groups. Wills (1969) considered this ratio to be a good measure of the calcium excretion rate in 'spot' urine samples. Results are similar to those found by Nordin et al. (1967) and by Dauncey & Widdowson (1972). Serum calciums (Table 4) were within the normal ranges given by Briscoe & Ragan (1967) and Lindgarde
616
N. J. Birch, A. A. Greenfield and R. P. Hullin Table 4. Serum calcium and Mg mmoljl. Mean ± S.D. (number of subjects in parentheses) Premenopausal female
Male Present Li series
Ca Mg Present Paget's survey Ca Mg
2-53 ±0-12(29) O-882±OO53 (29)
1
2-50 ± 0 1 1 (24) 0-868 ± 0 0 5 2 (24) 2-50 ±0-05(3) 0-828±0-027 (3)
Postmenopausal female 2-52 ± 0 1 1 (37) 0-876* ± 0 0 5 0 (37) 2-48 ±0-19(80) 0-845*±0083 (80)
P < 0-05 (t test).
(1972). Although there is a wide range of accepted normal values for serum magnesium (Seelig & Berger, 1974), much of the variation being attributable to methodology prior to atomic absorption spectroscopy (Rousselet & Durlach, 1971), the results are within the range of 0-80-95 mmol/1 reported by Wacker & Parisi (1968). There were no significant correlations between the rate of lithium excretion (CLI/threat) and the excretion rates of other measured variables (l/ x /t/ Creat ) except in the case of magnesium (P < 001) and urea (P < 005). The clearance of lithium was significantly correlated (P ranging from < 005 to < 0001) with the clearance fraction (Rx) of sodium, potassium, magnesium, calcium, phosphate, chloride, urea and creatinine in males and premenopausal females and (except for sodium, magnesium and calcium) in postmenopausal females. We consider this as evidence that lithium excretion is controlled by general renal efficiency not by some specific mechanism (Birch et al. 1977). The mean serum electrolytes for all the lithiumtreated patients were within the normal range but the mean serum magnesium of the postmenopausal females was significantly higher (P < 0-05, / test) than in those of the Paget's Disease survey. DISCUSSION The results of this study show that no major changes in urinary excretion of calcium and magnesium occur during long-term lithium treatment. However, in spite of reservations concerning the sensitivity and validity of 'spot' urine sampling, the conclusions of Wills (1969) with respect to this technique were confirmed. The high correlation between urine excretion rates as determined by the reported time of sample and by creatinine excretion rate indicates that the 'spot' technique may be useful for a large group of subjects when
the urinary determinations are processed simultaneously by a well controlled laboratory over a relatively short period. Most studies of lithium effects have been carried out at the start of, or in the early stages of, lithium treatment. This study, in contrast, has investigated a large number of patients who have been receiving lithium for many years when a steady state might be thought to exist although the concept of equilibrium on a multiple dosage schedule is of doubtful validity. A large number of biochemical variables has also been used. Pharmacodynamic aspects of lithium treatment arising from our study will be discussed in a separate paper (Birch et(al. 1977). (a) Calcium
The results show that the excretion and serum concentrations of calcium are normal during lithium treatment despite previous findings from acute studies in animals of increased serum concentrations and excretions of calcium following lithium administration (Andreoli et al. 1972). Carman et al. (1974) have in fact proposed a prediction of 'anti-depressant' response to lithium based on the serum Ca/Mg ratio during thefirstfivedays of lithium treatment. Crammer (1975) has also reported a fall in urinary calcium following the commencement of lithium therapy. Possible explanations for this are that increased calcium excretion may occur only at higher lithium doses, a species difference in sensitivity to lithium may exist, or, more probably, that early metabolic effects adapt to equilibrium after an initial period of treatment. However, Birch (1971) has reported one short-cycle manic-depressive male whose 24-hour calcium excretion rate fell markedly on the discontinuation of long-term lithium therapy although he was maintained under strict metabolic control. Despite being determined on spot urine samples and the absence of previous dietary
Biochemical screening in lithium prophylaxis
restriction, the calcium excretion rates found in this study agree with other workers (Table 3). Furthermore the urinary calcium/creatinine ratios and calcium clearances are in the normal range. The concurrent determination of creatinine with the excretory product of interest is valuable when accurately timed urine samples are not easily obtained. While no abnormality in calcium metabolism during lithium administration has been detected in this study, it should be noted that it is very difficult to detect osteomalacia or osteoporosis by biochemical screening since very small longterm calcium decrements occur rather than a measurable elevation or depression of urinary or serum levels (Gallagher et al. 1972). The effects of continual small changes in calcium metabolism would only be detected over a lengthy period. We are presently undertaking long-term radiological investigations in both human subjects and rats to detect any effect of prophylactic lithium on bone. (b) Magnesium The role of magnesium in the pharmacology of lithium has been discussed by Birch (1974a) and Birch & Jenner (1973). A number of reports describe an increase in plasma magnesium following short-term lithium (Nielsen, 1964; Bunney et al. 1968; Aronoff et al. 1971; Andreoli et al. 1972; Birch & Jenner, 1973). However, no correlation between serum lithium and magnesium concentrations has been found in this study. This is in agreement with a report by Dunner et al. (1975) who suggest that a return to the pre-lithium steady state magnesium concentration must occur following an initial increase. Patients in our control Paget's Disease survey, however, had lower mean serum magnesium concentration in both premenopausal and postmenopausal females than the respective lithium groups, though the difference was statistically significant only in the postmenopausal group. Lithium does not appear to have a simple doseeffect relationship with serum magnesium and further work is required in this area. Our thanks are due to the patients who co-operated in this investigation and to Dr R. McDonald, medical director, who was clinically responsible for these out-patients. We wish also to acknowledge the invaluable assistance of the nursing staff of the Regional Metabolic Research Unit and the staff of the Path40
617
ology Laboratory, High Royds Hospital, Menston, Ilkley. The study was supported by an MRC programme grant to R.P.H., Reader in Biochemistry and Wellcome Research Fellow, University of Leeds. REFERENCES Andreoli, V. M., Villani, F. & Brambilla, G. (1972). Increased magnesium and calcium excretion induced by lithium carbonate. Psychopharmacologia 25, 77-85. Aronoff, M. S., Evens, R. G. & Durell, J. (1971). Effect of lithium salts on electrolyte metabolism. Journal of Psychiatric Research 8, 139-159. Baron, D. N. (1970). A Short Textbook of Chemical Pathology (2nd edn). English Universities Press: London. Birch, N. J. (1970). Lithium and plasma magnesium. British Journal of Psychiatry 116, 461. Birch, N. J. (1971). A study of the effects of lithium salts on the distribution and excretion of other ions. Ph.D. Thesis, University of Sheffield. (British Library, Lending Division, Boston Spa, Yorkshire. Microfilm No. D3225/73.) Birch, N. J. (1974a). Lithium and magnesium dependent enzymes. Lancet ii, 965-966. Birch, N. J. (19746). Lithium accumulation in bone after oral administration in rat and in man. Clinical Science and Molecular Medicine 46, 409-413. Birch, N. J. & Hullin, R. P. (1972). The distribution and binding of lithium following its long-term administration. Life Sciences 11, 1095-1099. Birch, N. J. & Jenner, F. A. (1973). The distribution of lithium and its effects on the distribution and excretion of other ions in the rat. British Journal of Pharmacology 47, 586-594. Birch, N. J., Greenfield, A. A. & Hullin, R. P. (1974). A metabolic profile of patients receiving prophylactic lithium therapy. British Journal of Pharmacology 52, 443P. Birch, N. J., Greenfield, A. A. & Hullin, R. P. (1977). Pharmacodynamic aspects of lithium prophylaxis. Submitted for publication. Briscoe, A. M. & Ragan, C. (1967). Relation of magnesium to calcium in human blood serum. Nature 214, 1126-1127. Bunney, W. E., Goodwin, F. K., Davis, J. M. & Fawcett, J. A. (1968). A behavioural-biochemical study of lithium treatment. American Journal of Psychiatry 125, 499-512. Carman, J. S., Post, R. M., Teplitz, T. A. & Goodwin, F. K. (1974). Divalent cations in predicting antidepressant response to lithium. Lancet ii, 1454. Crammer, J. (1975). Lithium, calcium and mental illness. Lancet i, 215-216. Creek, R. D., Lund, P., Thomas, D. P. & Pollard, W. O. (1971). The effect of lithium carbonate on eggshell formation and serum calcium level of the hen. Poultry Science 50, 577-580. Dauncey, M. J. & Widdowson, E. M. (1972). Urinary excretion of calcium, magnesium, sodium and potassium in hard and soft water areas. Lancet i, 711-714. DuBois, D. & DuBois, E. F. (1916). Clinical calorimetry. A formula to estimate the approximate surface area if height and weight be known. Archives of Internal Medicine 17, 863-871. Dunner, D. L., Meltzer, H. L., Schreiner, H. C. & Fiegelson, J. L. (1975). Plasma and erythrocyte magnesium levels in patients with primary affective disorder during chronic lithium treatment. Ada Psychiatrica Scandinavica 51, 104109. Eastham, R. D. (1971). Biochemical Values in Clinical Medicine (4th edn). John Wright: Bristol. Frausto da Silva, J. J. R. & Williams, R. J. P. (1976). Possible mechanism for the biological action of lithium. Nature 263, 237-239. PSM 7
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Gallagher, J. C , Young, M. M. & Nordin, B. E. C. (1972). The effect of artificial menopause on plasma and urine calcium and phosphate. Clinical Endocrinology 1, 57-64. Gotfredsen, C. F. & Rafaelsen, O. J. (1970). Effect of lithium and other psychopharmaca on rat electrolyte metabolism. International Pharmacopsychiatry 5, 242-248. Hullin, R. P., McDonald, R. & Allsopp, M. N. E. (1975). Further report on prophylactic lithium in recurrent affective disorders. British Journal of Psychiatry 126, 281284. Lindgarde, F. (1972). Potentiometric determination of serum ionized calcium in a normal human population. Clinica Chimica Ada 40, 477-484. Mellerup, E. T. & Plenge, P. (1976). Lithium effects on magnesium, calcium and phosphate metabolism in rats. International Pharmacopsychiatry 11, 190-195. Mellerup, E. T., Plenge, P., Ziegler, R. & Rafaelsen, O. J. (1970). Lithium effects on calcium metabolism in rats. International Pharmacopsychiatry 5, 258-264. Nielsen, J. (1964). Magnesium lithium studies. I. Serum and erythrocyte magnesium in patients with manic states during lithium treatment. Ada Psychiatrica Scandinavica 40, 190-196. Nordin, B. E. C , Hodgkinson, A. & Peacock, M. (1967). The measurement and the meaning of urinary calcium. Clinical Orthopaedics 52, 293-322.
Rousselet, F. & Durlach, J. (1971). Mdthodes analytiques et exploration practique du metabolisme du magnesium en clinique humaine. \er. Symposium International sur le Deficit Magnesique en Pathologie Humaine 1, Volume des Rapports (ed. J. Durlach), pp. 65-90. S.G.E.M.V.: Vittel. Schou, M. (1968). Lithium in psychiatric therapy and prophylaxis. Journal of Psychiatric Research 6, 67-95. Scott, J. T., Fergusson, T. M., Bradley, J. W. & Greger, C. R. (1973). The effects of low levels of lithium chloride in the diet of the laying hen. Poultry Science 52, 2336-2337. Seelig, M. S. & Berger, A. R. (1974). Range of normal serum magnesium values. New England Journal of Medicine 290, 974-975. Shaw, D. M. (1973). Effects of lithium salts on amine metabolism and electrolytes. Biochemistry Society Transactions 1,78-81. Varley, H. (1967). Practical Clinical Biochemistry (4th edn). Heinemann: London. Wacker, W. E. C. & Parisi, A. F. (1968). Magnesium metabolism. New England Journal of Medicine 278, 658-663. Wills, M. R. (1969). The urinary calcium/creatinine ratio as a measure of urinary calcium excretion. Journal of Clinical Pathology 22, 287-290.
Lithium therapy and alkaline earth metal metabolism: a biochemical screening study N. J. BIRCH, x A. A. GREENFIELD AND R. P. HULLIN From the Department of Biochemistry, University of Leeds, and the Computing and Statistics Section, British Iron and Steel Research Association, Sheffield
A study is described of 90 patients receiving lithium prophylactically for recurrent affective disorder. A total of 90 biochemical variables was analysed by correlation matrices. No abnormality in calcium or magnesium metabolism was detected though this may merely be a reflection of the insensitivity of the screening technique used.
SYNOPSIS
INTRODUCTION Theories of the mode of action of lithium salts in manic-depressive psychoses suggest that lithium interacts with either the alkali metals sodium and potassium or with the biogenic amines (Shaw, 1973). It has also been proposed that its mode of action might be due to the 'diagonal' relationship in the periodic table between lithium and the alkaline earth metals, magnesium and calcium (Birch, 1970, 1974 a; Frausto da Silva & Williams, 1976). Young rats, treated for periods of 28 days with lithium, have been reported to have a decreased concentration of calcium in bone (Birch & Jenner, 1973). The occurrence of a similar effect in mature humans during lithium therapy would represent a long-term side effect which requires investigation. Various effects of lithium on alkaline earth metal metabolism have been reported in the literature. Both decreased uptake of 48Ca, MMg and ^P by rat bone and increased phosphate uptake in rat diaphragm occur following lithium administration (Mellerup et al. 1970; Gotfredsen & Rafaelsen, 1970; Mellerup & Plenge, 1976). Other authors (Andreoli et al. 1972; Gotfredsen & Rafaelsen, 1970; Aronoff et al. 1971; Birch & Jenner, 1973) have also reported increased excretion of the alkaline earth metals following lithium treatment in man and in animals. The production of soft-shelled eggs in the domestic fowl given 1 Address for correspondence: DrN. J. Birch, Department of Biochemistry, University of Leeds, 9 Hyde Terrace, Leeds LS2 9LS.
lithium (Creek et al. 1971) has not been confirmed by Scott et al. (1973) with a lower dosage of lithium. Many of these findings arise from studies of relatively immature animals and might not apply to pre-existing bone, but evidence of pharmacological effects of lithium on calcified tissues in animals indicates the importance of such studies on human subjects receiving longterm lithium treatment. The accumulation of lithium in the bones of rats and adult human subjects (Birch & Hullin, 1972; Birch; 19746) also makes such investigations necessary. An attempt has therefore been made to investigate biochemical effects of lithium in a group of 90 out-patients receiving maintenance lithium therapy. This group, which had been receiving lithium for an average period of 3 years (range 0-5-9 years), visited our lithium clinic regularly for monitoring and thus the whole group could be seen over a relatively short period. Many members of this group had shown a marked prophylactic action of lithium against unipolar and bipolar affective illness (Hullin et al. 1975) and it was therefore essential to prevent patients refusing treatment because of long-term side effects which might not be established by this or subsequent investigations. To avoid alarming the patients, therefore, only the normal routine blood sample, and an additional spot urine sample were taken. The restricted information obtainable from a random urine sample was accepted as a price which had to be paid for a rapid screening test of any gross disturbance in electrolyte excretion. We appreciated the imprecision of the technique
613
614
N. J. Birch, A. A. Greenfield and R. P. Hullin
and thus had some expectations of failure to show significant conclusions. In the event the results showed that the technique of 'spot' urine sampling is capable of giving results which are internally consistent and also agree with other workers. This technique may be of value in other outpatient studies and in the case of uncooperative or incontinent patients; previously it has been reported as a valid technique for the screening of calcium excretion (Wills, 1969). Throughout this paper the following abbreviations will be used: M = male, F P r e = premenopausal female, F P o s t = postmenopausal female, Cx = clearance of x, Rx = clearance of x/clearance of creatinine, Ux = urine concentration of x, Px = plasma or serum concentration of x, Tx = excretion rate of x with respect to time. A preliminary report of part of this study has been previously presented (Birch et al. 1974). METHOD Out-patients attend the lithium clinic at intervals of 4^10 weeks depending on age, stability of standard lithium levels and psychiatric state. A blood sample is taken for the determination of serum lithium and the patient is interviewed. In this study, 25 ml of blood was taken from an antecubital vein, into a plain tube, and a urine sample obtained in a suitable container. The patients were informed that the urine sample was required for an investigation of electrolyte excretion during lithium therapy and all consented. Since the only difference from a normal visit was the provision of a sample of urine, the procedure was accepted as routine and unremarkable. To minimize diurnal and dietary variations, patients were only included in the series if their blood and urine specimens were collected between 09.00 and 12.00 hours. To avoid seasonal variations the samples were collected over an 8-week period in early summer. Lithium, sodium, potassium, magnesium, calcium, phosphate, chloride, creatinine and urea were determined in serum and urine, in all cases. Cations were determined by atomic absorption spectroscopy (Unicam SP90) using dilutents previously described (Birch & Jenner, 1973). Chloride was determined by EEL model 240 chloride meter. Phosphate, creatinine, urea and serum alkaline phosphatase were determined by methods described by Varley (1967).
At the interview the following data were obtained: weight, height, time since last intake of lithium, and time since last micturition. The latter information, based on patient's recollection, was used as an additional basis for excretion rates. During a subsequent visit, gynaecological and obstetric histories were obtained from female patients. Age, period on lithium and psychiatric history were obtained from records. The data were numerically coded and processed from this point with no further reference to named patients. Completed analyses and full information were obtained from 90 of 110 patients from whom samples were obtained and statistical analyses were carried out on this data set. The remaining subjects were excluded either because they were unable to produce a urine sample or because the serum obtained was insufficient for the determination of all the variables. Algebraic transformations were carried out to determine rates of excretion, with respect to time (Tx) and creatinine excretion (£/x/C/Creat). Clearance values (Cx) were calculated on the assumption that the determined plasma concentration was representative of the whole period of urine collection. The clearance fraction with respect to creatinine clearance was also calculated (CJ Ccreat = Rx). The dose was recalculated in terms of body weight and surface area, the latter from the formula of DuBois & DuBois (1916). The statistical analysis was carried out by correlation coefficients determined in various combinations of a 35 x 35 matrix using an IBM 1800 computer. A limited biochemical survey was also carried out to identify cases of Paget's Disease in the long-stay female wards of the psychiatric hospital, though none was found. The serum calciums, magnesiums, ureas and alkaline phosphatases as determined in the same laboratory contemporaneously with the present study, are reported as a non-matched control series to show that the results as determined were within the normal ranges for the laboratory and within accepted normal ranges. RESULTS The composition of the series (Table 1) was as expected for the known occurrence of this group of disorders (Schou, 1968). Females outnumber males by about two to one and there is a pre-
Biochemical screening in lithium prophylaxis
615
Table 1. Composition of patient series. Values are given as means + S.D.
Male Premenopausal female Postmenopausal female All female Combined male and female
No.
Age (years)
29 24 37 61 90
52-9±13-4 36-9±8-l 60-9±7-8 51-l±14-3 5l-7±13-94
Height (cm) 173-7+.8-3 162-9±6-2 156-4±7-4 159-1 ±7-6 163-8± 10-4
Weight (kg)
Surface area
77-3±12-4 64-8±150 66-l±10-2 65-5±12-3 69-3+.13-5
l-910±0-176 l-689±O18O l-659±O-143 l-671±0158 1-749+0199
Table 2. Mean ± S.D. values of variables in male, premenopausal and postmenopausal groups Male (N = 29) U. vol (ml) Period of specimen (h) Time since last Li dose (h) Time on Li (months) Dose Li (mg Li.CO,) Dose Li/kg body weight Dose Li/m$ body area
139-4±116-9 1-718± 1-185
3-982±4-18 30-25±26-76 813-7±199-5 10-76±2-962 427-7±1050
Premenopausal female (N = 24)
Postmenopausal female (N = 37)
1240± 118-6 2099±1199 4-260+.4-701 13-58±14-I3 7760+. 260-2 12-30±4-489 460-6± 154-6
1480± 124-6 2076±1029 6-90±7-89 3704±22-23 666-6± 178-8 10-27±3-108 4020± 106-4
Table 3. Urinary calcium I creatinine excretion ratio. Mean ± S.D. mgCa/mg creatinine (number of subjects in parentheses) Male
Premenopausal female
Postmenopausal female
Present Li series
0151±0120(29)
0172±0113(29)
0122±0061 (37)
Nordine/a/. (1967) Dauncey & Widdowson (1972)
O163±OO82(1O4) 0-15^-016(9)
dominance of postmenopausal females. The mean age and standard deviation of the total male and female groups is very similar. The mean age of the menopause for the post-menopausal female group elicited by interview was 44-6 ±9-4 years. Mean values of some of the variables in the male, premenopausal and postmenopausal female groups are given in Table 2. The smallest urine volume recorded was 25 ml. The agreement between excretion rate as obtained from the patient's report and from urine volume/creatinine ratio was surprisingly good. Correlations between the two measures were significant in the male and premenopausal females (P < 001), in the postmenopausal females (P < 0001), total females and total subjects. Thus, the patients appear to have reported their previous time of micturition with reasonable accuracy. No significant correlation was found between
0156±0069(88)
calcium excretion rate and serum lithium, lithium excretion rate, lithium dose however expressed, and period of lithium treatment. The calcium values determined were within the normal range. Serum alkaline phosphatase was within the normal limits given by Eastham(1971) (4-5-9-5 KingArmstrong Units/100 ml) in all except 12 subjects (M = 2, F P r e = 3, F P o s t = 7). Of these one F P r e was slightly below the range, but she and all except one .Fpost subject were within the range suggested by Baron (1970) (3-13 King-Armstrong Units). Table 3 shows the urinary Ca/creatinine ratios of the various groups. Wills (1969) considered this ratio to be a good measure of the calcium excretion rate in 'spot' urine samples. Results are similar to those found by Nordin et al. (1967) and by Dauncey & Widdowson (1972). Serum calciums (Table 4) were within the normal ranges given by Briscoe & Ragan (1967) and Lindgarde
616
N. J. Birch, A. A. Greenfield and R. P. Hullin Table 4. Serum calcium and Mg mmoljl. Mean ± S.D. (number of subjects in parentheses) Premenopausal female
Male Present Li series
Ca Mg Present Paget's survey Ca Mg
2-53 ±0-12(29) O-882±OO53 (29)
1
2-50 ± 0 1 1 (24) 0-868 ± 0 0 5 2 (24) 2-50 ±0-05(3) 0-828±0-027 (3)
Postmenopausal female 2-52 ± 0 1 1 (37) 0-876* ± 0 0 5 0 (37) 2-48 ±0-19(80) 0-845*±0083 (80)
P < 0-05 (t test).
(1972). Although there is a wide range of accepted normal values for serum magnesium (Seelig & Berger, 1974), much of the variation being attributable to methodology prior to atomic absorption spectroscopy (Rousselet & Durlach, 1971), the results are within the range of 0-80-95 mmol/1 reported by Wacker & Parisi (1968). There were no significant correlations between the rate of lithium excretion (CLI/threat) and the excretion rates of other measured variables (l/ x /t/ Creat ) except in the case of magnesium (P < 001) and urea (P < 005). The clearance of lithium was significantly correlated (P ranging from < 005 to < 0001) with the clearance fraction (Rx) of sodium, potassium, magnesium, calcium, phosphate, chloride, urea and creatinine in males and premenopausal females and (except for sodium, magnesium and calcium) in postmenopausal females. We consider this as evidence that lithium excretion is controlled by general renal efficiency not by some specific mechanism (Birch et al. 1977). The mean serum electrolytes for all the lithiumtreated patients were within the normal range but the mean serum magnesium of the postmenopausal females was significantly higher (P < 0-05, / test) than in those of the Paget's Disease survey. DISCUSSION The results of this study show that no major changes in urinary excretion of calcium and magnesium occur during long-term lithium treatment. However, in spite of reservations concerning the sensitivity and validity of 'spot' urine sampling, the conclusions of Wills (1969) with respect to this technique were confirmed. The high correlation between urine excretion rates as determined by the reported time of sample and by creatinine excretion rate indicates that the 'spot' technique may be useful for a large group of subjects when
the urinary determinations are processed simultaneously by a well controlled laboratory over a relatively short period. Most studies of lithium effects have been carried out at the start of, or in the early stages of, lithium treatment. This study, in contrast, has investigated a large number of patients who have been receiving lithium for many years when a steady state might be thought to exist although the concept of equilibrium on a multiple dosage schedule is of doubtful validity. A large number of biochemical variables has also been used. Pharmacodynamic aspects of lithium treatment arising from our study will be discussed in a separate paper (Birch et(al. 1977). (a) Calcium
The results show that the excretion and serum concentrations of calcium are normal during lithium treatment despite previous findings from acute studies in animals of increased serum concentrations and excretions of calcium following lithium administration (Andreoli et al. 1972). Carman et al. (1974) have in fact proposed a prediction of 'anti-depressant' response to lithium based on the serum Ca/Mg ratio during thefirstfivedays of lithium treatment. Crammer (1975) has also reported a fall in urinary calcium following the commencement of lithium therapy. Possible explanations for this are that increased calcium excretion may occur only at higher lithium doses, a species difference in sensitivity to lithium may exist, or, more probably, that early metabolic effects adapt to equilibrium after an initial period of treatment. However, Birch (1971) has reported one short-cycle manic-depressive male whose 24-hour calcium excretion rate fell markedly on the discontinuation of long-term lithium therapy although he was maintained under strict metabolic control. Despite being determined on spot urine samples and the absence of previous dietary
Biochemical screening in lithium prophylaxis
restriction, the calcium excretion rates found in this study agree with other workers (Table 3). Furthermore the urinary calcium/creatinine ratios and calcium clearances are in the normal range. The concurrent determination of creatinine with the excretory product of interest is valuable when accurately timed urine samples are not easily obtained. While no abnormality in calcium metabolism during lithium administration has been detected in this study, it should be noted that it is very difficult to detect osteomalacia or osteoporosis by biochemical screening since very small longterm calcium decrements occur rather than a measurable elevation or depression of urinary or serum levels (Gallagher et al. 1972). The effects of continual small changes in calcium metabolism would only be detected over a lengthy period. We are presently undertaking long-term radiological investigations in both human subjects and rats to detect any effect of prophylactic lithium on bone. (b) Magnesium The role of magnesium in the pharmacology of lithium has been discussed by Birch (1974a) and Birch & Jenner (1973). A number of reports describe an increase in plasma magnesium following short-term lithium (Nielsen, 1964; Bunney et al. 1968; Aronoff et al. 1971; Andreoli et al. 1972; Birch & Jenner, 1973). However, no correlation between serum lithium and magnesium concentrations has been found in this study. This is in agreement with a report by Dunner et al. (1975) who suggest that a return to the pre-lithium steady state magnesium concentration must occur following an initial increase. Patients in our control Paget's Disease survey, however, had lower mean serum magnesium concentration in both premenopausal and postmenopausal females than the respective lithium groups, though the difference was statistically significant only in the postmenopausal group. Lithium does not appear to have a simple doseeffect relationship with serum magnesium and further work is required in this area. Our thanks are due to the patients who co-operated in this investigation and to Dr R. McDonald, medical director, who was clinically responsible for these out-patients. We wish also to acknowledge the invaluable assistance of the nursing staff of the Regional Metabolic Research Unit and the staff of the Path40
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ology Laboratory, High Royds Hospital, Menston, Ilkley. The study was supported by an MRC programme grant to R.P.H., Reader in Biochemistry and Wellcome Research Fellow, University of Leeds. REFERENCES Andreoli, V. M., Villani, F. & Brambilla, G. (1972). Increased magnesium and calcium excretion induced by lithium carbonate. Psychopharmacologia 25, 77-85. Aronoff, M. S., Evens, R. G. & Durell, J. (1971). Effect of lithium salts on electrolyte metabolism. Journal of Psychiatric Research 8, 139-159. Baron, D. N. (1970). A Short Textbook of Chemical Pathology (2nd edn). English Universities Press: London. Birch, N. J. (1970). Lithium and plasma magnesium. British Journal of Psychiatry 116, 461. Birch, N. J. (1971). A study of the effects of lithium salts on the distribution and excretion of other ions. Ph.D. Thesis, University of Sheffield. (British Library, Lending Division, Boston Spa, Yorkshire. Microfilm No. D3225/73.) Birch, N. J. (1974a). Lithium and magnesium dependent enzymes. Lancet ii, 965-966. Birch, N. J. (19746). Lithium accumulation in bone after oral administration in rat and in man. Clinical Science and Molecular Medicine 46, 409-413. Birch, N. J. & Hullin, R. P. (1972). The distribution and binding of lithium following its long-term administration. Life Sciences 11, 1095-1099. Birch, N. J. & Jenner, F. A. (1973). The distribution of lithium and its effects on the distribution and excretion of other ions in the rat. British Journal of Pharmacology 47, 586-594. Birch, N. J., Greenfield, A. A. & Hullin, R. P. (1974). A metabolic profile of patients receiving prophylactic lithium therapy. British Journal of Pharmacology 52, 443P. Birch, N. J., Greenfield, A. A. & Hullin, R. P. (1977). Pharmacodynamic aspects of lithium prophylaxis. Submitted for publication. Briscoe, A. M. & Ragan, C. (1967). Relation of magnesium to calcium in human blood serum. Nature 214, 1126-1127. Bunney, W. E., Goodwin, F. K., Davis, J. M. & Fawcett, J. A. (1968). A behavioural-biochemical study of lithium treatment. American Journal of Psychiatry 125, 499-512. Carman, J. S., Post, R. M., Teplitz, T. A. & Goodwin, F. K. (1974). Divalent cations in predicting antidepressant response to lithium. Lancet ii, 1454. Crammer, J. (1975). Lithium, calcium and mental illness. Lancet i, 215-216. Creek, R. D., Lund, P., Thomas, D. P. & Pollard, W. O. (1971). The effect of lithium carbonate on eggshell formation and serum calcium level of the hen. Poultry Science 50, 577-580. Dauncey, M. J. & Widdowson, E. M. (1972). Urinary excretion of calcium, magnesium, sodium and potassium in hard and soft water areas. Lancet i, 711-714. DuBois, D. & DuBois, E. F. (1916). Clinical calorimetry. A formula to estimate the approximate surface area if height and weight be known. Archives of Internal Medicine 17, 863-871. Dunner, D. L., Meltzer, H. L., Schreiner, H. C. & Fiegelson, J. L. (1975). Plasma and erythrocyte magnesium levels in patients with primary affective disorder during chronic lithium treatment. Ada Psychiatrica Scandinavica 51, 104109. Eastham, R. D. (1971). Biochemical Values in Clinical Medicine (4th edn). John Wright: Bristol. Frausto da Silva, J. J. R. & Williams, R. J. P. (1976). Possible mechanism for the biological action of lithium. Nature 263, 237-239. PSM 7
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Gallagher, J. C , Young, M. M. & Nordin, B. E. C. (1972). The effect of artificial menopause on plasma and urine calcium and phosphate. Clinical Endocrinology 1, 57-64. Gotfredsen, C. F. & Rafaelsen, O. J. (1970). Effect of lithium and other psychopharmaca on rat electrolyte metabolism. International Pharmacopsychiatry 5, 242-248. Hullin, R. P., McDonald, R. & Allsopp, M. N. E. (1975). Further report on prophylactic lithium in recurrent affective disorders. British Journal of Psychiatry 126, 281284. Lindgarde, F. (1972). Potentiometric determination of serum ionized calcium in a normal human population. Clinica Chimica Ada 40, 477-484. Mellerup, E. T. & Plenge, P. (1976). Lithium effects on magnesium, calcium and phosphate metabolism in rats. International Pharmacopsychiatry 11, 190-195. Mellerup, E. T., Plenge, P., Ziegler, R. & Rafaelsen, O. J. (1970). Lithium effects on calcium metabolism in rats. International Pharmacopsychiatry 5, 258-264. Nielsen, J. (1964). Magnesium lithium studies. I. Serum and erythrocyte magnesium in patients with manic states during lithium treatment. Ada Psychiatrica Scandinavica 40, 190-196. Nordin, B. E. C , Hodgkinson, A. & Peacock, M. (1967). The measurement and the meaning of urinary calcium. Clinical Orthopaedics 52, 293-322.
Rousselet, F. & Durlach, J. (1971). Mdthodes analytiques et exploration practique du metabolisme du magnesium en clinique humaine. \er. Symposium International sur le Deficit Magnesique en Pathologie Humaine 1, Volume des Rapports (ed. J. Durlach), pp. 65-90. S.G.E.M.V.: Vittel. Schou, M. (1968). Lithium in psychiatric therapy and prophylaxis. Journal of Psychiatric Research 6, 67-95. Scott, J. T., Fergusson, T. M., Bradley, J. W. & Greger, C. R. (1973). The effects of low levels of lithium chloride in the diet of the laying hen. Poultry Science 52, 2336-2337. Seelig, M. S. & Berger, A. R. (1974). Range of normal serum magnesium values. New England Journal of Medicine 290, 974-975. Shaw, D. M. (1973). Effects of lithium salts on amine metabolism and electrolytes. Biochemistry Society Transactions 1,78-81. Varley, H. (1967). Practical Clinical Biochemistry (4th edn). Heinemann: London. Wacker, W. E. C. & Parisi, A. F. (1968). Magnesium metabolism. New England Journal of Medicine 278, 658-663. Wills, M. R. (1969). The urinary calcium/creatinine ratio as a measure of urinary calcium excretion. Journal of Clinical Pathology 22, 287-290.
