Acta pharmacol. et toxicol. 1975, 36, 181-186.
From the Department of Pharmacology, University of Helsinki, Siltavuorenpenger 10, SF-00170 Helsinki 10, Finland
Effect of Food and Repeated Injections on Serum Diazepam Levels BY
M. Linnoila, K. Korttila and M. J. Mattila (Received August 13, 1974; Accepted September 16, 1974)
Diazepam 0.3 mg/kg was administered intravenously three times at intervals of 14 days into seven healthy volunteers. Five hours after injection the subjects ingested either 330 ml of mineral water, mineral water in combination with 2 rusks, or 330 ml of fatty milk with an egg hamburger. Diazepam and N- desmethyldiazepam levels were measured in serum samples drawn at 4 , 5 , 6 , 7 and 8 hours after administration of the drug. At the same time the ability to discriminate flickering light was measured, and the feeling of tiredness was recorded. The serum diazepam levels declined regularly as a function of time after mineral water, but both kinds of food significantly elevated the serum diazepam level from the sixth hour onwards. The ability to discriminate flickering light was not modified. Serum N-desmethyldiazepam levels were significantly elevated after the second and third injections as compared with the first injection. Serum diazepam levels were not lowered. The present findings could be explained by an enterohepatic cycle of diazepam, and suggest that diazepam might induce its own metabolism in man. Abstract:
Key-words: Serum diazepam - food intake - repeated injections - kinetics.
Diazepam is generally used intravenously for minor out-patient surgery. A delayed recovery after intravenous diazepam has been demonstrated to coincide with increasing serum levels of the drug from 6 hours on after injection (BAIRD & HAILEY1972). This phenomenon has been attributed t o an enterohepatic cycle of diazepam (KLEIJNet al. 1971). On the other hand, diazepam administered over long term periods for psychiatric outpatients has been demonstrated to induce its own metabolism (KANTOet al. 1974). The present cross-over study was conducted in order to investigate the effect of food on serum levels of diazepam and N-desmethyldiazepam after intravenous diazepam. The other point of interest was a possible hastened metabolism of diazepam after repeated injections.
M. LINNOILA, K. KORTTILA AND M. J. MATTILA
182
Material and Methods The subjects were seven paid healthy volunteers, six males and one female. Their characteristics were as follows (mean+ S.D.):
Height (cm) 176 5.6
+
Weight (kg) 63.8 k 11.8
Age (years) 21.4+ 1.7
Smoking habits 10-20 cigarettes/day (one abstainer)
None of the subjects had previous experience with diazepam. All of them showed normal values of serum transaminases. Experimental design. Diazepam 5 mg/ml (Orion, Helsinki) was injected in a dose of 0.3 mg/kg into a large antecubital vein within 4 minutes. Each subject received three injections at intervals of 14 days. Blood samples were drawn 4 , 5 , 6 , 7 and 8 hours after the injections. Serum diazepam and N-desmethyldiazepam levels were measured after extraction by gas chromatography (ZINGALES 1973). The ability to discriminate the flickering light was measured immediately after the venipuncture. The feeling of tiredness was also recorded (KORTTILA& LINNOILA1914). The effect of food was investigated by administering to the subjects five hours after the injection in cross-over randomized order (Latin square) either 330 ml of mineral water, or mineral water in combination with two rusks, or 330 ml of fatty milk with an egg hamburger. A possible more rapid metabolism of diazepam after repeated injections was investigated by comparing the serum levels of diazepam and N-desmethyldiazepam, respectively, following the first, second and third injection. The statistical treatment of the data was according to Student’s t-test, because their quality was in favour of this method.
Results After mineral water the serum diazepam concentrations decreased rather regularly as a function of time from fourth hour onwards (fig. 1). After rusks or an egg hamburger the serum levels of diazepam were statistically significantly elevated from the sixth hour onwards as compared with the levels measured after mineral water (fig. 1). At 6 hours the serum diazepam levels after rusks or hamburger were elevated as compared with their respective four-hour-values, but this difference did not reach statistical significance. The serum levels of Ndesmethyldiazepam were not modified by food (fig. 1). After the second and third injections, the serum N-desmethyldiazepam levels were significantly increased at any time of measurement as compared with the respective values after the first injection (fig. 2). However the serum diazepam levels were not diminished. The ability to discriminate flickering light did not correlate with the serum levels of diazepam or N-desmethyldiazepam. All subjects reported fatigue after
183
FOOD AND SERUM DIAZEPAM
T
ng/ml
401
301
-=ScD
---- --ScND
201
m e a n t SE
1
L
x = Fat a = Carbohydrate o = Mineralwater
101
+'t
I
5
6
- i
1
8
c
Time in hours
Fig. 1. Serum diazepam and N-desmethyldiazepam levels after different foods. The levels of significance are computed against values measured after the intake of mineral water. * = P < 0.05, ** =P < 0.01. Because of the similarity of the N-desmethyldiazepam levels corresponding S.E.M. ranges are not indicated. SeD =serum diazepam level, SeND = serum N-desmethyldiazepam level.
rusks or hamburger at 6 hours after the injection. No one reported it at the same time after mineral water.
Discussion
It has been suggested that in man diazepam may be excreted in bile and reabsorbed from the intestine (KLEIJNet al. 1971). An increase in the serum diazepam levels was demonstrated in four out of five volunteers at six hours
184
M. LINNOILA, K. KORTTILA AND M. J. MATTILA
ng/m I
LOO
---- =ScND mean*
SE
x = I injection 0 = II injection
o= 111 injection
hours Fig. 2. The effect of repeated injections on serum diazepam and N-desmethyldiazepam levels. The levels of significance are computed against the values measured after the first injection. * = P < 0.05. Because of the similarity of the diazepam levels corresponding S.E.M.ranges are not indicated. SeD =serum diazepam level, SeND =serum N- desmethyldiazepam level.
after intravenous injection by BAIRD& HAILEY(1972). In a previous report from this laboratory (KORTTILA& LINNOILA1974) four out of 21 subjects showed increased serum diazepam level from six hours onwards. With repeated injections this phenomenon varied from subject to subject (KORTTILA& LINNOILA1974). The subjects were allowed t o eat at four hours, and in this experiment the type of the food was not controlled. The type of food may have modified the serum diazepam levels inter-individually and between the repeated injections intra-individually in previous studies. Hence, in the present trial the food chosen was either a known chole-
FOOD AND SERUM DIAZEPAM
185
kinetic one (fatty with egg hamburger) or one with as little cholekinetic characteristics as possible (mineral water) (WHITESIDE 1969). Mineral water administered at five hours after intravenous diazepam was not followed by elevated serum diazepam levels at six hours as in the case of rusks or milk with hamburger (fig. 1). This finding is in favour of an enterohepatic cycle of diazepam. Serum N-desmethyldiazepam levels were significantly increased after the second and third injections as compared with the situation after the first injection. Thus, a single intravenous injection of diazepam may induce its metabolism for at least two weeks. Another explanation for the elevated serum Ndesmethyldiazepam levels is a “subthreshold” saturation of tissues with this metabolite, the next booster resulting in elevated serum levels. Because of the randominzation of the drinks and food according to Latin square the enzyme induction and the type of food should not have had any significant interaction on the present results. Subjectively the elevated serum diazepam levels were manifested as fatigue after rusks or hamburger at six hours after injection. The ability to discriminate flickering light was not, however, significantly altered during elevated serum diazepam concentrations at that time. This may be due to the CNS being most sensitive to the initial rise of serum diazepam after administration (LINNOILA & MATTILA1973). On the other hand the dose-response relationship of diazepam on flicker-fusion is such, that the dose of diazepam used is beyond the most sensitive range of the test (KORTTILA & LINNOILA, 1975). Hence the present results do not reveal the practical significance of the late increase in serum diazepam concentration on human psychomotor performance.
REFERENCES Baird, E. S. & D. M. Hailey: Delayed recovery from a sedative: correlation of the plasma levels of diazepam with clinical effects after oral and intravenous administration. Brit. J. Anaesth. 1972, 44, 803-808. Kanto, J., I. Iisalo, V. Lehtinen & J. Salminen: The concentrations of diazepam and its metabolites in the plasma after an acute and chronic administration. Psychopharmacol. 1974, 36, 123-131. Van der Kleijn, E., J. M. van Rossum, E. T. J. M. Muskens, N. V. M. Rijntjes: Pharmacokinetics of diazepam in dogs, mice and humans. Actapharmacol. et toxicol. 1971, 21, SUPPI, 3, 109-127. Korttila, K. & M. Linnoila: Skills related to driving after intravenous diazepam, flunitrazepam or droperidol. Brit. J. Anaesth. 1974, in press. Korttila, K. & M. Linnoila: Recovery and skills related to driving after intravenous sedation: A dose response relationship with diazepam. Brit J. Anaeseth. 1975, in press. Linnoila, M. & M. J. Mattila: Drug interaction on psychomotor skills related to driving: Diazepam and alcohol. Eur. J. Clin. Pharmacol. 1973, 5 , 186-194.
186
M. LINNOILA, K. KORTTILA AND M. J. MATTILA
Whiteside, C. G.: The biliary tract, pancreas, liver and spleen. In: Textbook of radiology. Ed.: D. Sutton. Livingstone, Edinburgh and London, 1969, pp. 720-754. Zingales, I. A. : Diazepam metabolism during chronic medication. Unbound fraction in plasma, erythrocytes and urine. J. Chromatogr. 1973, 75, 55-78.
From the Department of Pharmacology, University of Helsinki, Siltavuorenpenger 10, SF-00170 Helsinki 10, Finland
Effect of Food and Repeated Injections on Serum Diazepam Levels BY
M. Linnoila, K. Korttila and M. J. Mattila (Received August 13, 1974; Accepted September 16, 1974)
Diazepam 0.3 mg/kg was administered intravenously three times at intervals of 14 days into seven healthy volunteers. Five hours after injection the subjects ingested either 330 ml of mineral water, mineral water in combination with 2 rusks, or 330 ml of fatty milk with an egg hamburger. Diazepam and N- desmethyldiazepam levels were measured in serum samples drawn at 4 , 5 , 6 , 7 and 8 hours after administration of the drug. At the same time the ability to discriminate flickering light was measured, and the feeling of tiredness was recorded. The serum diazepam levels declined regularly as a function of time after mineral water, but both kinds of food significantly elevated the serum diazepam level from the sixth hour onwards. The ability to discriminate flickering light was not modified. Serum N-desmethyldiazepam levels were significantly elevated after the second and third injections as compared with the first injection. Serum diazepam levels were not lowered. The present findings could be explained by an enterohepatic cycle of diazepam, and suggest that diazepam might induce its own metabolism in man. Abstract:
Key-words: Serum diazepam - food intake - repeated injections - kinetics.
Diazepam is generally used intravenously for minor out-patient surgery. A delayed recovery after intravenous diazepam has been demonstrated to coincide with increasing serum levels of the drug from 6 hours on after injection (BAIRD & HAILEY1972). This phenomenon has been attributed t o an enterohepatic cycle of diazepam (KLEIJNet al. 1971). On the other hand, diazepam administered over long term periods for psychiatric outpatients has been demonstrated to induce its own metabolism (KANTOet al. 1974). The present cross-over study was conducted in order to investigate the effect of food on serum levels of diazepam and N-desmethyldiazepam after intravenous diazepam. The other point of interest was a possible hastened metabolism of diazepam after repeated injections.
M. LINNOILA, K. KORTTILA AND M. J. MATTILA
182
Material and Methods The subjects were seven paid healthy volunteers, six males and one female. Their characteristics were as follows (mean+ S.D.):
Height (cm) 176 5.6
+
Weight (kg) 63.8 k 11.8
Age (years) 21.4+ 1.7
Smoking habits 10-20 cigarettes/day (one abstainer)
None of the subjects had previous experience with diazepam. All of them showed normal values of serum transaminases. Experimental design. Diazepam 5 mg/ml (Orion, Helsinki) was injected in a dose of 0.3 mg/kg into a large antecubital vein within 4 minutes. Each subject received three injections at intervals of 14 days. Blood samples were drawn 4 , 5 , 6 , 7 and 8 hours after the injections. Serum diazepam and N-desmethyldiazepam levels were measured after extraction by gas chromatography (ZINGALES 1973). The ability to discriminate the flickering light was measured immediately after the venipuncture. The feeling of tiredness was also recorded (KORTTILA& LINNOILA1914). The effect of food was investigated by administering to the subjects five hours after the injection in cross-over randomized order (Latin square) either 330 ml of mineral water, or mineral water in combination with two rusks, or 330 ml of fatty milk with an egg hamburger. A possible more rapid metabolism of diazepam after repeated injections was investigated by comparing the serum levels of diazepam and N-desmethyldiazepam, respectively, following the first, second and third injection. The statistical treatment of the data was according to Student’s t-test, because their quality was in favour of this method.
Results After mineral water the serum diazepam concentrations decreased rather regularly as a function of time from fourth hour onwards (fig. 1). After rusks or an egg hamburger the serum levels of diazepam were statistically significantly elevated from the sixth hour onwards as compared with the levels measured after mineral water (fig. 1). At 6 hours the serum diazepam levels after rusks or hamburger were elevated as compared with their respective four-hour-values, but this difference did not reach statistical significance. The serum levels of Ndesmethyldiazepam were not modified by food (fig. 1). After the second and third injections, the serum N-desmethyldiazepam levels were significantly increased at any time of measurement as compared with the respective values after the first injection (fig. 2). However the serum diazepam levels were not diminished. The ability to discriminate flickering light did not correlate with the serum levels of diazepam or N-desmethyldiazepam. All subjects reported fatigue after
183
FOOD AND SERUM DIAZEPAM
T
ng/ml
401
301
-=ScD
---- --ScND
201
m e a n t SE
1
L
x = Fat a = Carbohydrate o = Mineralwater
101
+'t
I
5
6
- i
1
8
c
Time in hours
Fig. 1. Serum diazepam and N-desmethyldiazepam levels after different foods. The levels of significance are computed against values measured after the intake of mineral water. * = P < 0.05, ** =P < 0.01. Because of the similarity of the N-desmethyldiazepam levels corresponding S.E.M. ranges are not indicated. SeD =serum diazepam level, SeND = serum N-desmethyldiazepam level.
rusks or hamburger at 6 hours after the injection. No one reported it at the same time after mineral water.
Discussion
It has been suggested that in man diazepam may be excreted in bile and reabsorbed from the intestine (KLEIJNet al. 1971). An increase in the serum diazepam levels was demonstrated in four out of five volunteers at six hours
184
M. LINNOILA, K. KORTTILA AND M. J. MATTILA
ng/m I
LOO
---- =ScND mean*
SE
x = I injection 0 = II injection
o= 111 injection
hours Fig. 2. The effect of repeated injections on serum diazepam and N-desmethyldiazepam levels. The levels of significance are computed against the values measured after the first injection. * = P < 0.05. Because of the similarity of the diazepam levels corresponding S.E.M.ranges are not indicated. SeD =serum diazepam level, SeND =serum N- desmethyldiazepam level.
after intravenous injection by BAIRD& HAILEY(1972). In a previous report from this laboratory (KORTTILA& LINNOILA1974) four out of 21 subjects showed increased serum diazepam level from six hours onwards. With repeated injections this phenomenon varied from subject to subject (KORTTILA& LINNOILA1974). The subjects were allowed t o eat at four hours, and in this experiment the type of the food was not controlled. The type of food may have modified the serum diazepam levels inter-individually and between the repeated injections intra-individually in previous studies. Hence, in the present trial the food chosen was either a known chole-
FOOD AND SERUM DIAZEPAM
185
kinetic one (fatty with egg hamburger) or one with as little cholekinetic characteristics as possible (mineral water) (WHITESIDE 1969). Mineral water administered at five hours after intravenous diazepam was not followed by elevated serum diazepam levels at six hours as in the case of rusks or milk with hamburger (fig. 1). This finding is in favour of an enterohepatic cycle of diazepam. Serum N-desmethyldiazepam levels were significantly increased after the second and third injections as compared with the situation after the first injection. Thus, a single intravenous injection of diazepam may induce its metabolism for at least two weeks. Another explanation for the elevated serum Ndesmethyldiazepam levels is a “subthreshold” saturation of tissues with this metabolite, the next booster resulting in elevated serum levels. Because of the randominzation of the drinks and food according to Latin square the enzyme induction and the type of food should not have had any significant interaction on the present results. Subjectively the elevated serum diazepam levels were manifested as fatigue after rusks or hamburger at six hours after injection. The ability to discriminate flickering light was not, however, significantly altered during elevated serum diazepam concentrations at that time. This may be due to the CNS being most sensitive to the initial rise of serum diazepam after administration (LINNOILA & MATTILA1973). On the other hand the dose-response relationship of diazepam on flicker-fusion is such, that the dose of diazepam used is beyond the most sensitive range of the test (KORTTILA & LINNOILA, 1975). Hence the present results do not reveal the practical significance of the late increase in serum diazepam concentration on human psychomotor performance.
REFERENCES Baird, E. S. & D. M. Hailey: Delayed recovery from a sedative: correlation of the plasma levels of diazepam with clinical effects after oral and intravenous administration. Brit. J. Anaesth. 1972, 44, 803-808. Kanto, J., I. Iisalo, V. Lehtinen & J. Salminen: The concentrations of diazepam and its metabolites in the plasma after an acute and chronic administration. Psychopharmacol. 1974, 36, 123-131. Van der Kleijn, E., J. M. van Rossum, E. T. J. M. Muskens, N. V. M. Rijntjes: Pharmacokinetics of diazepam in dogs, mice and humans. Actapharmacol. et toxicol. 1971, 21, SUPPI, 3, 109-127. Korttila, K. & M. Linnoila: Skills related to driving after intravenous diazepam, flunitrazepam or droperidol. Brit. J. Anaesth. 1974, in press. Korttila, K. & M. Linnoila: Recovery and skills related to driving after intravenous sedation: A dose response relationship with diazepam. Brit J. Anaeseth. 1975, in press. Linnoila, M. & M. J. Mattila: Drug interaction on psychomotor skills related to driving: Diazepam and alcohol. Eur. J. Clin. Pharmacol. 1973, 5 , 186-194.
186
M. LINNOILA, K. KORTTILA AND M. J. MATTILA
Whiteside, C. G.: The biliary tract, pancreas, liver and spleen. In: Textbook of radiology. Ed.: D. Sutton. Livingstone, Edinburgh and London, 1969, pp. 720-754. Zingales, I. A. : Diazepam metabolism during chronic medication. Unbound fraction in plasma, erythrocytes and urine. J. Chromatogr. 1973, 75, 55-78.
