Pharmacokinetics of Alcohol Following Single low Doses to Fasted and Nonfasted Subjects PETER G. WELLING, Ph.D.. 1. 1. LYONS, B.S., R. ELLIOTT, M.S.. and GORDON 1. AMIDON. Ph.D. Madison, Wis.
is now common knowledge that the Iorallyabsorption and circulating levels of ingested ethyl alcohol are reduced T
in the presence of food.14 Reduced alcohol rbsorption may be due to delayed stomach aptying, reduced ability of alcohol to reach the epithelial lining of the gastrointestinal tract, oxidation by food components, or a combination of these factors. Studies concerning alcohol absorption have hitherto been complicated by the pharmacokinetic characteristics attributed to this compound. Alcohol is known to dehy stomach emptying and to inhibit its own absorption after high doses,l while the metabolic clearance of alcohol obeys Hiehaelis-Mentenkinetics and is saturable rt high Thus, the interpretation ot any alcohol absorption study using high doses is necessarily complicated by the contribution of these factors to apparent bioavailability characteristics. In the present study, we have examined the absorption of alcohol in both fasted md nonfasted subjects following single, bw doses. By this procedure, we can describe the bioavailability characteristiles of alcohol with minimal interference due to drug-induced changes in the abmrption and elimination processes. 7
hin the Center for Health Sciences, School of pharmacy, University of Wisconsin, Madison, Ti Study supported by National Institute6 of Mth Orant G.M. 20327.
April, 1977 from the SAGE Social Science Collections. All Rights Reserved.
Material and Methods The subjects were one female and five male healthy volunteers between 18 and 32 years of age (mean 26 years) and weighing between 59 and 89 kg (mean 68 kg) who were shown by medical examination to be in good physical condition, with normal blood and urine biochemistry. None of the subjects smoked, but they all drank small amounts of alcohol socially. Protocol. The protocol followed was similar to those used in previous studies.'#* Verbal assurance was obtained from all subjects that they had taken no known enzyme-inducing agents for one month, and no drugs, including alcohol for one week, preceding the study. Subjects were instructed to take no drugs other than the required doses of alcohol during the study. Subjects were fasted overnight before each treatment and were not permitted to eat, apart from the test meals, until 4 hours after dosing. On the morning of a study, the subjects drank 250 ml water on arising, at least 1 hour before dosing. Alcohol was administered at 8 A.M., and blood samples ( 4 3 ml) were obtained from a forearm vein by means of an indwelling catheter immediately before and at intervals up to 3 hours after dosing, as indicated in Table I. Thus, each subject gave one predose and 18 postdose samples for each treat.ment. Blood was collected in 199
W E L L I X G , L Y O N S , ELLIOTT, A N D AMIDON
TABLE I Average Serum Alcohol Ccd Serum alcohol (mgi100 ml) at indicated times after alcohol i n g d Treatment
3min
5min
1Omin
15min
20min
25min
30min
1. Carbohydrate
0.2 (0.4)
0.5 (0.9)
0.5 (0.9)
0.4 (0.6)
0.4 (0.5)
0.6 (0.8)
0.3 (0.4)
2. Fat
0.1 (0.0)
1.0 (0.9)
2.1 (1.9)
1.7 (1.9)
2.3 (2.2)
2.0 (2.4)
(2.2)
3. Protein
0.8 (1.3)
4.4 (7.0)
6.9 (5.9)
6.8 (4.6)
5.3 (3.7)
5.1 (3.1)
4.2 (2.8)
4. Fasting
0.1 (0.1)
7.1 (4.5)
4.5 (2.9)
9.8 (7.1)
11.7 (7.7)
15.6 (6.4)
16.1
NSD**
NSD
3>2; 4>1
3>1,2; 4>1
3,4>1,2
3>1,2; 4>1-3
Paired t-test among treatments
* Less than
1.8
(3.6) 3>1,2;
4>13
0.1 mg/100 ml.
** NSD=No significant difference.
syringes containing no anticoagulant, and serum was separated and deep frozen ( - 22OC) until assayed. Indwelling catheters were rinsed with 2 ml sterile physiologic saline solution containing 10 units sodium heparin per ml between each sampling time. Care was taken to ensure complete removal of this solution from the catheter before taking a blood sample. Treatments. I n all treatments, subjects received alcohol at a dose of 0.2 ml 95% alcohol per kg body weight, equivalent to 14 ml in a 70-kg subject. The alcohol was flavored with pure lemon juice (5 ml) and sugar (2 Gm) and diluted to 150 ml with water. This solution was then administered immediately after standardized high carbohydrate (treatment 1), high fat (treatment 2), o r high protein (treatment 3) solid meals, which were prepared exactly as described p r e v i ~ u s l y , ~ or. ~on an empty stomach (treatment 4). All meals were prepared by special arrangement with the University of Wisconsin Hospital cafeteria and were standardized as closely 200
as possible regarding total weight, caloric value, and fluid volume. Subjects received each treatment once, and treatments were administered four days apart. All subjects received the same treatment at the same time. Assay of Serum Samples. Serums were assayed for alcohol content by the method of Gupta and associate^.^ The method was modified in that t-butyl alcohol was sub stituted for isopropyl alcohol as internal standard. Gas chromatography was carried out on a nuclear Chicago Model 5000 instrument with flame ionization detector using a 6-foot by 2-mm I.D. U-shaped glass column packed with uncoated Chromosorb 102, 60/80 mesh. The oven temperature was 15OoC, while injector port and detector temperatures were 18OOC. Gas flow rates were 25 ml/min for nitrogen, 20 ml/min for hydrogen, and 400 ml/min for air. I n this system, retention times of ethyl alcohol and t-butyl alcohol were 82 and 190 seconds, respectively. The linear regression of peak height The Journal of Clinical Pharmacology
PHARMACOKINETICS OF ALCOHOL
from All Treatments Serum alcohol (mg/100 mi) at indicated times after alcohol ingestion 6omin
70min
80min
90min
0.5 (0.7)
0.4 (0.6)
0.2 (0.2)
0.1 (0.1)
0.7
0.4 (0.6)
0.2
(0.9)
(0.2)
1.1 (0.8)
0.8 (0.5)
0.5 (0.3)
0.3 (0.2)
0.1 (0.1)
9.8
8.4 (3.1)
6.9 (2.9)
5.0 (2.0)
4.1 (2.1)
(2.6) 4>1-3
4>1-3
3>1,2; 4> 1-3
100min
140min
160min
180min
-*
-
-
-
-
0.2
0.1
-
-
-
-
(0.2)
(0.0)
-
-
-
-
2.9 (1.6)
2.1 (0.8)
1.5 (0.5)
1.1 (0.5)
4>1-3
4>13
4>1-3
3>1; 4>1-3
ratios of ethyl alcohol:internal standard against alcohol serum concentrations, from 0.5 to 20.0 mg per 100 ml, was y = 0.043 t 17.5s ( r = + 0.99, n= 60). The average value ( C standard deviation) of peak height ratio divided by known serum dcohol concentration was 17.42%0.16 (r=60),and there were no concentrationdependent trends in this value. biterpetation of Results. Serum alcohol levels at each sampling time, and also peak serum levels, times of peak levels, and areas under serum level curves measured by the trapezoidal rule, were compared among treatments by analysis of variance. If differences due to treatments were obtained, results from individual treatments were compared by paired t-test. The varied nature of serum alcohol pro6les in all nonfasting treatments precluded detailed pharmacokinetic analysis of these data. Serum alcohol concentrations in fasted subjects were fitted to eqs. (1) and (2) by graphic analysis: April, 1977
120min
4>1-3
4>1-3
Improved estimates of pharmacokinetic parameters were obtained using the iterative nonlinear regression program NREG on a Univac digital computer.7J0 Equation (1) is appropriate to the onecompartment open model with first-order absorption and elimination, where C is the serum alcohol concentration at any time t after dosing, F is the fraction of the dose D absorbed, V is the apparent distribution volume of alcohol in the body, and 12 and K are first-order rate constants for alcohol absorption and elimination, respectively.ll The use of this type of equation was possible due to lack of saturation of alcohol metabolism with the low serum levels obtained in’this study. The rate constant K in both cqs. (1) and (2) is equivalent to the Michaelis201
WELLING, LYONS, ELLIOTT, A N D AMIDON
Menten function V,,,/K,,, obtained from higher alcohol doses.’-6 Equation (2) is appropriate to the one-compartment open model with zeroorder absorption and first-order elimination, where ko is the zero-order rate constant for alcohol absorption, t’ is the time period to completion of the absorption process, and f‘ is the time after absorption has stopped. Other symbols are as described for eq. (1).I n both equations, a lag time, tlag,is included to represent the time interval between dosing and the appearance of alcohol in serum.
1..
YD
Results Mean serum alcohol levels from all treatments are given in Table I, and individual values are shown in Fig. 1. Comparison of the data shows that, with the low dose used, food had a dramatic effect on serum alcohol levels. With the exception of subject M.D., the high protein meal caused a reduction in overall serum levels to about one quarter those obtained in fasted subjects. The high fat meal caused a further reduction in serum levels, while the high carbohydrate meal inhibited absorption to such a n extent that essentially zero serum alcohol levels were obtained in three subjects. Despite the marked reduction in serum alcohol levels in nonfasted subjects, peak serum levels, where they could be measured, occurred at similar or earlier times compared t o those in fasted subjects (Table 11). Table I11 summarizes the results of pharmacokinetic analysis of data from treatment 4. Both of the proposed models fitted the data reasonably well. However, the slightly better coeficients of determination, f , and also reduced variance of individual parameter values with the zero-order absorption model (not shown i n the table) suggest that this model is the more appropriate. I n addition, the zero-order model has fewer parameters 202
1
BC
, :(i TIYE WIN1
Fig. 1. Individual serum levels of alcohol after a dose of 0.2 ml 95% alcohol per kg to fasted subjects (-) and nonfasted sdjeck followiag high carbohydrate (---), high fat (-), and high protein (- * - meals. a)
(ko/V, K ) than the first-order model ( F D / V , k, K ) . Thus, from a modeling point of view, the zero-order case is preferable. The relative accuracy of the two models is indicated for two representative sub jects in Fig. 2. It is clear from this figure that, although both models fitted the data quite well, the zero-order model resulted in closer agreement between actual and model-predicted values around the peak of the serum level curves. This was the case for five of the six subjects; for the sixth subject, both models resulted in excellent agreement between actual and predicted values. The Journal of Clinical Pharmacolog
PHARNACOEINETICS OF ALCOHOL
TABLE I1 Pharmacokinetic Parameters (A 1 S.D.)from All Treatment8 Treatment Parameter
Peak height (mg/100
4
Time of peak height (min)
2
3
4
1.3 +- 1.3
2.8 +. 2.1
8225.9
17.8e4.4
38 -C 26
23f9
18 k 16
28f7
NSD
249 +- 162
1090_e 257
3>1,2; 4>1-3
41 f37 ~~~~~~
Paired t-test
1
105 f109
3>1,2; 4>1-3
~
Obtained by trapezoidal rule.
TABLE I11 Pharmacokinetic Parameters (r+ 1 S.D.)from Treatment 4 Using First-Order and Zero-Order Absorption Models
Parameter
First-order absorption (using eq. (1))
Zero-order absorption (using eq. (2))
0.09 f e0.08
-
13.5 +- 8.6
-
P
-
426 +- 136
-
0.029 e0.001
0.020 f0.006
is now common knowledge that the Iorallyabsorption and circulating levels of ingested ethyl alcohol are reduced T
in the presence of food.14 Reduced alcohol rbsorption may be due to delayed stomach aptying, reduced ability of alcohol to reach the epithelial lining of the gastrointestinal tract, oxidation by food components, or a combination of these factors. Studies concerning alcohol absorption have hitherto been complicated by the pharmacokinetic characteristics attributed to this compound. Alcohol is known to dehy stomach emptying and to inhibit its own absorption after high doses,l while the metabolic clearance of alcohol obeys Hiehaelis-Mentenkinetics and is saturable rt high Thus, the interpretation ot any alcohol absorption study using high doses is necessarily complicated by the contribution of these factors to apparent bioavailability characteristics. In the present study, we have examined the absorption of alcohol in both fasted md nonfasted subjects following single, bw doses. By this procedure, we can describe the bioavailability characteristiles of alcohol with minimal interference due to drug-induced changes in the abmrption and elimination processes. 7
hin the Center for Health Sciences, School of pharmacy, University of Wisconsin, Madison, Ti Study supported by National Institute6 of Mth Orant G.M. 20327.
April, 1977 from the SAGE Social Science Collections. All Rights Reserved.
Material and Methods The subjects were one female and five male healthy volunteers between 18 and 32 years of age (mean 26 years) and weighing between 59 and 89 kg (mean 68 kg) who were shown by medical examination to be in good physical condition, with normal blood and urine biochemistry. None of the subjects smoked, but they all drank small amounts of alcohol socially. Protocol. The protocol followed was similar to those used in previous studies.'#* Verbal assurance was obtained from all subjects that they had taken no known enzyme-inducing agents for one month, and no drugs, including alcohol for one week, preceding the study. Subjects were instructed to take no drugs other than the required doses of alcohol during the study. Subjects were fasted overnight before each treatment and were not permitted to eat, apart from the test meals, until 4 hours after dosing. On the morning of a study, the subjects drank 250 ml water on arising, at least 1 hour before dosing. Alcohol was administered at 8 A.M., and blood samples ( 4 3 ml) were obtained from a forearm vein by means of an indwelling catheter immediately before and at intervals up to 3 hours after dosing, as indicated in Table I. Thus, each subject gave one predose and 18 postdose samples for each treat.ment. Blood was collected in 199
W E L L I X G , L Y O N S , ELLIOTT, A N D AMIDON
TABLE I Average Serum Alcohol Ccd Serum alcohol (mgi100 ml) at indicated times after alcohol i n g d Treatment
3min
5min
1Omin
15min
20min
25min
30min
1. Carbohydrate
0.2 (0.4)
0.5 (0.9)
0.5 (0.9)
0.4 (0.6)
0.4 (0.5)
0.6 (0.8)
0.3 (0.4)
2. Fat
0.1 (0.0)
1.0 (0.9)
2.1 (1.9)
1.7 (1.9)
2.3 (2.2)
2.0 (2.4)
(2.2)
3. Protein
0.8 (1.3)
4.4 (7.0)
6.9 (5.9)
6.8 (4.6)
5.3 (3.7)
5.1 (3.1)
4.2 (2.8)
4. Fasting
0.1 (0.1)
7.1 (4.5)
4.5 (2.9)
9.8 (7.1)
11.7 (7.7)
15.6 (6.4)
16.1
NSD**
NSD
3>2; 4>1
3>1,2; 4>1
3,4>1,2
3>1,2; 4>1-3
Paired t-test among treatments
* Less than
1.8
(3.6) 3>1,2;
4>13
0.1 mg/100 ml.
** NSD=No significant difference.
syringes containing no anticoagulant, and serum was separated and deep frozen ( - 22OC) until assayed. Indwelling catheters were rinsed with 2 ml sterile physiologic saline solution containing 10 units sodium heparin per ml between each sampling time. Care was taken to ensure complete removal of this solution from the catheter before taking a blood sample. Treatments. I n all treatments, subjects received alcohol at a dose of 0.2 ml 95% alcohol per kg body weight, equivalent to 14 ml in a 70-kg subject. The alcohol was flavored with pure lemon juice (5 ml) and sugar (2 Gm) and diluted to 150 ml with water. This solution was then administered immediately after standardized high carbohydrate (treatment 1), high fat (treatment 2), o r high protein (treatment 3) solid meals, which were prepared exactly as described p r e v i ~ u s l y , ~ or. ~on an empty stomach (treatment 4). All meals were prepared by special arrangement with the University of Wisconsin Hospital cafeteria and were standardized as closely 200
as possible regarding total weight, caloric value, and fluid volume. Subjects received each treatment once, and treatments were administered four days apart. All subjects received the same treatment at the same time. Assay of Serum Samples. Serums were assayed for alcohol content by the method of Gupta and associate^.^ The method was modified in that t-butyl alcohol was sub stituted for isopropyl alcohol as internal standard. Gas chromatography was carried out on a nuclear Chicago Model 5000 instrument with flame ionization detector using a 6-foot by 2-mm I.D. U-shaped glass column packed with uncoated Chromosorb 102, 60/80 mesh. The oven temperature was 15OoC, while injector port and detector temperatures were 18OOC. Gas flow rates were 25 ml/min for nitrogen, 20 ml/min for hydrogen, and 400 ml/min for air. I n this system, retention times of ethyl alcohol and t-butyl alcohol were 82 and 190 seconds, respectively. The linear regression of peak height The Journal of Clinical Pharmacology
PHARMACOKINETICS OF ALCOHOL
from All Treatments Serum alcohol (mg/100 mi) at indicated times after alcohol ingestion 6omin
70min
80min
90min
0.5 (0.7)
0.4 (0.6)
0.2 (0.2)
0.1 (0.1)
0.7
0.4 (0.6)
0.2
(0.9)
(0.2)
1.1 (0.8)
0.8 (0.5)
0.5 (0.3)
0.3 (0.2)
0.1 (0.1)
9.8
8.4 (3.1)
6.9 (2.9)
5.0 (2.0)
4.1 (2.1)
(2.6) 4>1-3
4>1-3
3>1,2; 4> 1-3
100min
140min
160min
180min
-*
-
-
-
-
0.2
0.1
-
-
-
-
(0.2)
(0.0)
-
-
-
-
2.9 (1.6)
2.1 (0.8)
1.5 (0.5)
1.1 (0.5)
4>1-3
4>13
4>1-3
3>1; 4>1-3
ratios of ethyl alcohol:internal standard against alcohol serum concentrations, from 0.5 to 20.0 mg per 100 ml, was y = 0.043 t 17.5s ( r = + 0.99, n= 60). The average value ( C standard deviation) of peak height ratio divided by known serum dcohol concentration was 17.42%0.16 (r=60),and there were no concentrationdependent trends in this value. biterpetation of Results. Serum alcohol levels at each sampling time, and also peak serum levels, times of peak levels, and areas under serum level curves measured by the trapezoidal rule, were compared among treatments by analysis of variance. If differences due to treatments were obtained, results from individual treatments were compared by paired t-test. The varied nature of serum alcohol pro6les in all nonfasting treatments precluded detailed pharmacokinetic analysis of these data. Serum alcohol concentrations in fasted subjects were fitted to eqs. (1) and (2) by graphic analysis: April, 1977
120min
4>1-3
4>1-3
Improved estimates of pharmacokinetic parameters were obtained using the iterative nonlinear regression program NREG on a Univac digital computer.7J0 Equation (1) is appropriate to the onecompartment open model with first-order absorption and elimination, where C is the serum alcohol concentration at any time t after dosing, F is the fraction of the dose D absorbed, V is the apparent distribution volume of alcohol in the body, and 12 and K are first-order rate constants for alcohol absorption and elimination, respectively.ll The use of this type of equation was possible due to lack of saturation of alcohol metabolism with the low serum levels obtained in’this study. The rate constant K in both cqs. (1) and (2) is equivalent to the Michaelis201
WELLING, LYONS, ELLIOTT, A N D AMIDON
Menten function V,,,/K,,, obtained from higher alcohol doses.’-6 Equation (2) is appropriate to the one-compartment open model with zeroorder absorption and first-order elimination, where ko is the zero-order rate constant for alcohol absorption, t’ is the time period to completion of the absorption process, and f‘ is the time after absorption has stopped. Other symbols are as described for eq. (1).I n both equations, a lag time, tlag,is included to represent the time interval between dosing and the appearance of alcohol in serum.
1..
YD
Results Mean serum alcohol levels from all treatments are given in Table I, and individual values are shown in Fig. 1. Comparison of the data shows that, with the low dose used, food had a dramatic effect on serum alcohol levels. With the exception of subject M.D., the high protein meal caused a reduction in overall serum levels to about one quarter those obtained in fasted subjects. The high fat meal caused a further reduction in serum levels, while the high carbohydrate meal inhibited absorption to such a n extent that essentially zero serum alcohol levels were obtained in three subjects. Despite the marked reduction in serum alcohol levels in nonfasted subjects, peak serum levels, where they could be measured, occurred at similar or earlier times compared t o those in fasted subjects (Table 11). Table I11 summarizes the results of pharmacokinetic analysis of data from treatment 4. Both of the proposed models fitted the data reasonably well. However, the slightly better coeficients of determination, f , and also reduced variance of individual parameter values with the zero-order absorption model (not shown i n the table) suggest that this model is the more appropriate. I n addition, the zero-order model has fewer parameters 202
1
BC
, :(i TIYE WIN1
Fig. 1. Individual serum levels of alcohol after a dose of 0.2 ml 95% alcohol per kg to fasted subjects (-) and nonfasted sdjeck followiag high carbohydrate (---), high fat (-), and high protein (- * - meals. a)
(ko/V, K ) than the first-order model ( F D / V , k, K ) . Thus, from a modeling point of view, the zero-order case is preferable. The relative accuracy of the two models is indicated for two representative sub jects in Fig. 2. It is clear from this figure that, although both models fitted the data quite well, the zero-order model resulted in closer agreement between actual and model-predicted values around the peak of the serum level curves. This was the case for five of the six subjects; for the sixth subject, both models resulted in excellent agreement between actual and predicted values. The Journal of Clinical Pharmacolog
PHARNACOEINETICS OF ALCOHOL
TABLE I1 Pharmacokinetic Parameters (A 1 S.D.)from All Treatment8 Treatment Parameter
Peak height (mg/100
4
Time of peak height (min)
2
3
4
1.3 +- 1.3
2.8 +. 2.1
8225.9
17.8e4.4
38 -C 26
23f9
18 k 16
28f7
NSD
249 +- 162
1090_e 257
3>1,2; 4>1-3
41 f37 ~~~~~~
Paired t-test
1
105 f109
3>1,2; 4>1-3
~
Obtained by trapezoidal rule.
TABLE I11 Pharmacokinetic Parameters (r+ 1 S.D.)from Treatment 4 Using First-Order and Zero-Order Absorption Models
Parameter
First-order absorption (using eq. (1))
Zero-order absorption (using eq. (2))
0.09 f e0.08
-
13.5 +- 8.6
-
P
-
426 +- 136
-
0.029 e0.001
0.020 f0.006
