Pharmacokinetics and pharmacodynamics of oral diazepam: Effect of dose, plasma concentration, and time Eleven healthy subjects received single oral doses of placebo, 2 mg diazepam, 5 mg diazepam, and 10 mg diazepam in a randomized four-way crossover study. Plasma diazepam levels, the Digit Symbol Substitution Test (DSST), and fraction of total electroencephalographic (EEG) amplitude falling in the sigma plus beta (13 to 31 Hz) frequency range were determined during the 12 hours after drug administration. Peak plasma diazepam concentration and area under the 12-hour curve were proportional to dose; time of peak was independent of dose. Baseline percentage of EEG amplitude falling in the 13 to 31 Hz range averaged 15.7% and did not differ among the four trials. The percentage of EEG amplitude falling in the 13 to 31 Hz range did not change over baseline with placebo or 2 mg diazepam but was increased 1/4 to 21/2 hours after 5 mg diazepam, (maximum, + 7.3%) and 3/4 to 12 hours after 10 mg diazepam (maximum, + 15.2%). The increase in the percentage of EEG amplitude falling in the 13 to 31 Hz range was highly correlated with plasma diazepam concentration. DSST scores for placebo and 2 mg diazepam were nearly identical. DSST decrements with 5 and 10 mg diazepam paralleled and were correlated with the changes in the percentage of EEG amplitude falling in the 13 to 31 Hz range and with plasma diazepam levels. Thus the EEG analysis provides objective quantitation of benzodiazepine central nervous system effects, in turn reflecting plasma levels and other clinical measures. (CLIN PHARMACOL THER

1992;52:139-50.)

H. Friedman, David J. Greenblatt, Gary R. Peters, Carl M. Metzler, Melody D. Charlton, Jerold S. Harmatz, Edward J. Antal, Elmer C. Sanborn, and Steven F. Francom Kalamazoo, Mich., and Boston, Mass. Quantitative analysis of the time course of central effects of benzodiazepines in humans is of importance for understanding of both the clinical and the neurochemical actions of this class of compounds. Subjective and semiobjective measures of clinical response have been used in this context for many years.' Such measures include ratings of sedation and mood as rendered by the subject or by an observer, as well as alterations in tests of psychomotor performance or memory.2-1° These approaches have the advantage of being directly related to the primary clinical actions of From The Upjohn Co., Kalamazoo, and the Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine and New England Medical Center Hospital, Boston. Supported in part by grant MH-34223 from the U.S. Department of Health and Human Services. Received for publication Jan. 30, 1992; accepted April 12, 1992. Reprint requests: David J. Greenblatt, MD, Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111. 13/1/38604

the drug class, whether therapeutic, such as anxiolytic or calming effects, or potentially undesired, such as excess sedation or impairment of psychomotor performance. However, these methods also have disadvantages. Subjective ratings of mood and sedation may be influenced by the interpretations of rating scale items by individual subjects or patients. Psychomotor and memory testing procedures are influenced by practice effects, and drug responses may depend on population differences in baseline performance characteristics. Recent attention has focused on objective measures of quantitating the pharmacodynamic response to benzodiazepines. These include assessment of saccadic eye movement velocity, postural sway, and quantative analysis of the electroencephalogram (EEG).'8 These methods are essentially completely objective and are minimally, if at all, influenced by practice effects or placebo response. However, these measures are removed from the primary pharmacologic actions of the drug class and have sometimes been termed surrogate measures that are not necessarily relevant to

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HOURS AFTER DOSE Fig. 1. Plasma concentrations of diazepam (upper panel) and desmethyldiazepam (DMDZ; lower panel) after oral doses of 2 mg, 5 mg, and 10 mg diazepam. Each point is the mean value for all subjects at the corresponding time.

the primary sedative and anxiolytic effects of benzodi-

azepines. This study evaluated the pharmacokinetics of three usual therapeutic doses of oral diazepam (2 mg, 5 mg,

and 10 mg) in healthy human volunteers; these correspond to the dosage strengths that are available clinically. Plasma concentrations were evaluated simultaneously with a standard semiobjective laboratory test

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Table I. Pharmcokinetic variables for diazepam and desmethyldiazepam 2 mg

C,,a (ng/ml) C,,/Dose (ng/ml per

Mean ± SEM value 10 mg 5 mg 172 ± 12 34 ± 2

75 ± 7 38 ± 4

mg)

t

Diazepam 12-hr AUC (ng/ml hr) Diazepam AUC/dose (ng/ml hr per mg) Desmethyldiazepam I2-hr AUC (ng/ml hr) Desmethyldiazepam 12-hr AUC/Dose (ng/ml

0.89 ± 0.14 330 ± 24 165 ± 12 65 ± 16 hr per mg) 33 ± 8

Peak plasma diazepam concentration; NS, not significant;

1.00 ± 0.19 779 ± 63 156 ± 13 112 ± 17 22 ± 3

± ± ± ± 153 ±

317 32 1.32 1530

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Table II. Comparability of mean predose values in the four treatment conditions Mean ± SEM value

DSST score Number completed Number correct Percent 13 to 31 Hz EEG activity Randt test score

Placebo

2 mg

52.0 ± 4.5 51.7 ± 4.5 14.9 ± 1.6 6.7 ± 0.1

51.0 ± 3.9 50.7 ± 3.9 16.0 ± 2.3 6.5 ± 0.2

5 mg

51.9 51.6 16.0 6.7

± ± ± ±

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10 mg

F Value (ANOVA)

50.6 ± 4.3 49.8 ± 4.4 16.0 ± 1.9 6.5 ± 0.1

0.65 (NS) 0.93 (NS) 0.17 (NS) 1.37 (NS)

DSST, Digit Symbol Substitution Test: EEG, electroencephalographic.

of psychomotor performance, with self-ratings and observer ratings of sedation, and by quantitative analysis of the EEG.

METHODS Procedure. Eleven healthy volunteers (eight men and three women; age range, 19 to 35 years) participated after giving written informed consent. All were healthy, active, ambulatory adults with no evidence of medical disease who were receiving no other medications. They abstained from alcohol for at least 64 hours during each of the 4 trials, beginning at least 24 hours before admission and continuing throughout each entire trial. Subjects participated in a single-dose, randomized, four-way crossover study. The four treatment conditions were as follows: (1) placebo, (2) 2 mg diazepam, (3) 5 mg diazepam, and (4) 10 mg diazepam. All medications were identically packaged and were administered on a double-blind basis. At least 2 weeks elapsed between each of the four treatments to allow washout of diazepam and its metabolite, desmethyldiazepam, from previous doses. Subjects were admitted to the study unit at 5 PM the evening before each study day. They were provided dinner (a general diet) at 6 PM and a snack at 10 PM. They were then required to fast overnight (nothing to

eat or drink, including water) until 6 AM on each study day, at which time they ingested 8 ounces (240 ml) of orange juice. Subjects continued to fast until 4 hours after administration, at which time they resumed a normal (general) diet. The test medication was administered at approximately 8 AM on each study day, along with 6 ounces (180 ml) of water. Venous blood samples were drawn from an indwelling cannula before administration and at the following times after administration: 1/4, 1/2, 3/4, 1, 11/2, 2, 21/2, 3, 4, 6, 8, and 12 hours. Blood samples were centrifuged and the plasma separated and frozen until assayed for plasma drug concentrations. On the evening before medication administration, subjects performed the Randt Memory Test* (picture recognition, module 6) one time and the Digit Symbol Substitution Test (DSST)7 three times for practice and to minimize learning effects. The Randt test and DSST were also performed three times in the morning before medication administration and 12 times subsequent to dosing, at the times corresponding to blood sampling described above. Variations of the tests were administered for variety. The DSST was designed to evaluate changes in psychomotor performance, specif*1983, Life Science Associates, 11705.

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ically attention, concentration, focus and visual perception, and search and scanning ability. For each DSST, subjects were asked to accurately complete as many substitutions of symbols for numbers as possible in 90 seconds. Each test was scored as number of items completed and number of items correct. The Randt Memory Test provides convenient numeric indexes of short-term memory when subjects are tested for immediate visual recall of pictures of familiar objects. The subjects are randomly assigned to one of the five sets of pictures on flash cards and then move on to the next set. The subjects are told that the flash cards contain two sets of pictures: the first set of seven are to view and remember (2 seconds per picture), and the second 15 are to test the memory (3 seconds per card). The subjects verbally indicate recognition or not, while an observer keeps score of the total correct and the total false positives. The following additional mood and sedation evaluations were also performed once before dosage and again at the other 12 times corresponding to blood

sampling: the Upjohn short mood scale, a 32-item self-rated scale in which each item is rated by integers ranging from 0 ("not at all") to 4 ("extremely"); the volunteer visual analog mood and sedation scales described previously7; and the observer sedation effects assessment worksheet, in which a study observer rates a subject's degree of sedation on an integer scale ranging from 0 ("no sedation") to 5 ("unable to communicate"). This latter assessment was also performed 11/2 hours after awakening the following morning (1 hour before discharge). Three EEG electrodes were attached as follows: right occipital (02), active; right parietal (P4), indifferent; and ground electrode attached to the forehead. After the subjects rested quietly for several minutes with their eyes closed, a 31/2minute predose EEG recording was obtained from each volunteer with use of both analog magnetic tape and a standard paper recording. During all EEG recordings, volunteers rested quietly with eyes closed but were not allowed to sleep. All recordings of the EEG voltages were simul-

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