Comparative kinetics and dynamics of zaleplon, zolpidem, and placebo.
OBJECTIVE
This study evaluated the relationship of dose, plasma concentration, and time to the pharmacodynamics of zaleplon and zolpidem, 2 structurally distinct benzodiazepine receptor agonists.


METHODS
Ten healthy male volunteers received single oral doses of placebo, 10 mg zaleplon, 20 mg zaleplon, 10 mg zolpidem, and 20 mg zolpidem in a double-blind, 5-condition crossover study, with 48 hours elapsing between trials. Plasma drug concentrations and pharmacodynamic effects were measured during the 8 to 24 hours after administration.


RESULTS
Kinetics of zaleplon and zolpidem were not significantly related to dose. However, zaleplon had more rapid elimination (apparent elimination half-life [t1/2] of 1 hour) and higher apparent oral clearance (approximately 4300 mL/min) than zolpidem (t1/2, 2.0 to 2.2 hours; apparent oral clearance, 340 to 380 mL/min). Active treatments produced pharmacodynamic effects consistent with benzodiazepine agonist activity: self- and observer-rated sedation, impairment of digit symbol substitution test (DSST) performance, impaired memory, and increased electroencephalographic activity in the beta frequency range. The overall order of agonist potency was as follows: placebo < 10 mg zaleplon < 20 mg zaleplon < 10 mg zolpidem < 20 mg zolpidem; on a number of measures, 20 mg zaleplon was comparable to 10 mg zolpidem. Quantitative effects of zolpidem 20 mg far exceeded those of other treatments. Dynamic effects of both drugs were significantly related to plasma concentration.


CONCLUSIONS
Benzodiazepine agonist effects of zaleplon and zolpidem were dose and concentration dependent. At the usual clinically effective hypnotic dose (10 mg of either drug), agonist effects of zolpidem exceeded those of zaleplon.
Greenblatt
D J
DJ
Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, New England Medical Center Hospital, Boston 02111, USA. Dgreenblatt@infonet.tufts.edu
Harmatz
J S
JS
von Moltke
L L
LL
Ehrenberg
B L
BL
Harrel
L
L
Corbett
K
K
Counihan
M
M
Graf
J A
JA
Darwish
M
M
Mertzanis
P
P
Martin
P T
PT
Cevallos
W H
WH
Shader
R I
RI
D000081:Acetamides / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D000328:Adult; D014151:Anti-Anxiety Agents / Q000819:agonists; D001569:Benzodiazepines; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004569:Electroencephalography / Q000187:drug effects; D058785:GABA-A Receptor Agonists; D006801:Humans; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D008568:Memory / Q000187:drug effects; D011725:Pyridines / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D011743:Pyrimidines / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D012016:Reference Values; D000077334:Zolpidem
D000081:Acetamides; D014151:Anti-Anxiety Agents; D058785:GABA-A Receptor Agonists; D006993:Hypnotics and Sedatives; D011725:Pyridines; D011743:Pyrimidines; D001569:Benzodiazepines; D000077334:Zolpidem; C085665:zaleplon