Journal of Clinical Pharmacy and Therapeutics (1991) 1 6 , 4 1 4 4 . ADONIS 026947279 100006C
SOLID VERSUS LIQUID LITHIUM-A STUDY
PHARMACOKINETIC
H. R. Markar and G. Ascough Department of Psychiatry, Addenbrooke’s Hospital, University of Cambridge, Cambridge, U.K.
SUMMARY
T h e pharmacokinetics of solid lithium (Priadel) were compared with liquid lithium citrate in nine manic depressive patients. T h e results show that whilst the 12-h steady-state levels are similar, there are significant differences in the degree and rate of absorption between the two preparations. T h e clinical implications of this are discussed further. INTRODUCTION Lithium has an established place in the prophylaxis of manic depressive psychosis and has been in use for over 30 years. T h e majority of patients receive lithium in tablet form of which several preparations are available in the U.K. Unlike most other drugs, it has a narrow therapeutic range which means that levels above this could cause serious toxic effects whilst lower levels are ineffective. Moreover, a relationship has been claimed between serum levels and side-effects (1,2) and Scott (3) has pointed out that, different formulations of lithium may have different bioavailabilities. For these reasons it is essential that clinicians who prescribe lithium should have detailed knowledge of the pharmacokinetics of the various preparations available. Although lithium is used mainly in solid form, liquid preparations have a role in certain clinical situations. One such instance is clearly in patients who have difficulty in swallowing the large lithium tablets, e.g. the elderly (breaking the tablet into smaller pieces alters its pharmacokinetics and is not recommended). I t is also of use in the management of acute manic states where the possibility of checking the tablets (4) and discarding them later is quite common. T h e aim of this study is to compare the pharmacokinetics of liquid lithium with ‘Priadel’, which is a widely prescribed solid preparation, in patients already well stabilized on lithium. SUBJECTS AND METHODS Nine manic depressive patients (six in-patients, two day-patients and one out-patient) stabilized on prophylactic lithium (Priadel) were studied. Their mean age and weight were 43.3 years and 76 kg, respectively, and they were on a single daily dose of Priadel at Correspondence:H. R. Markar, Consultant Psychiatrist, QEII Hospital, Howlands, Welwyn Garden City, East Herts, U.K.
41
H. R. Markar and G . Ascough
42
Table 1. Mean value for 12-h serum levels, C,,,, T,,, and AUC ( n= 9) Priadel
Liquid lithium
12-h levels (mmol/litre)
0.60
0.55
Mean difference= 0.05, t = 1.74,NS.
C,, (mmol/litre)
1.12
1.37
Mean diffeience = 0.25, 95"" CI 0.09441, t =3,75, P
SOLID VERSUS LIQUID LITHIUM-A STUDY
PHARMACOKINETIC
H. R. Markar and G. Ascough Department of Psychiatry, Addenbrooke’s Hospital, University of Cambridge, Cambridge, U.K.
SUMMARY
T h e pharmacokinetics of solid lithium (Priadel) were compared with liquid lithium citrate in nine manic depressive patients. T h e results show that whilst the 12-h steady-state levels are similar, there are significant differences in the degree and rate of absorption between the two preparations. T h e clinical implications of this are discussed further. INTRODUCTION Lithium has an established place in the prophylaxis of manic depressive psychosis and has been in use for over 30 years. T h e majority of patients receive lithium in tablet form of which several preparations are available in the U.K. Unlike most other drugs, it has a narrow therapeutic range which means that levels above this could cause serious toxic effects whilst lower levels are ineffective. Moreover, a relationship has been claimed between serum levels and side-effects (1,2) and Scott (3) has pointed out that, different formulations of lithium may have different bioavailabilities. For these reasons it is essential that clinicians who prescribe lithium should have detailed knowledge of the pharmacokinetics of the various preparations available. Although lithium is used mainly in solid form, liquid preparations have a role in certain clinical situations. One such instance is clearly in patients who have difficulty in swallowing the large lithium tablets, e.g. the elderly (breaking the tablet into smaller pieces alters its pharmacokinetics and is not recommended). I t is also of use in the management of acute manic states where the possibility of checking the tablets (4) and discarding them later is quite common. T h e aim of this study is to compare the pharmacokinetics of liquid lithium with ‘Priadel’, which is a widely prescribed solid preparation, in patients already well stabilized on lithium. SUBJECTS AND METHODS Nine manic depressive patients (six in-patients, two day-patients and one out-patient) stabilized on prophylactic lithium (Priadel) were studied. Their mean age and weight were 43.3 years and 76 kg, respectively, and they were on a single daily dose of Priadel at Correspondence:H. R. Markar, Consultant Psychiatrist, QEII Hospital, Howlands, Welwyn Garden City, East Herts, U.K.
41
H. R. Markar and G . Ascough
42
Table 1. Mean value for 12-h serum levels, C,,,, T,,, and AUC ( n= 9) Priadel
Liquid lithium
12-h levels (mmol/litre)
0.60
0.55
Mean difference= 0.05, t = 1.74,NS.
C,, (mmol/litre)
1.12
1.37
Mean diffeience = 0.25, 95"" CI 0.09441, t =3,75, P
