Pharmacodynamics of triazolam after intravenous administration

Triazolam pharmacokinetics and effects on sedation, short-term amnesia, and psychomotor performance were evaluated in 25 normal volunteers as part of a safety and tolerance study of intravenous dosing of triazolam. Triazolam kinetics were linear after intravenous administration of doses up to 1.0 mg with no differences among doses in elimination half-life, volume of distribution, or clearance. The hepatic extraction ratio ranged from 0.14 to 0.37, suggesting that triazolam should undergo moderate first-pass metabolism after oral administration. The duration and extent of sedation, decrement in psychomotor performance test scores, and amnesia were dose related, but all subjects returned to baseline alertness and function within eight hours of dosing. The time-course of effects on memory and psychomotor performance were related to triazolam plasma concentration profile using an Emax model for effect and a two-compartment pharmacokinetic model. The probability of a subject being asleep was related to triazolam plasma concentrations using logistic regression. These models indicate that intravenous doses of 0.25 to 0.5 mg triazolam would be effective for use preoperatively for short surgical procedures.