Does potency determine amnestic effects of benzodiazepines? A dose-response comparison of flunitrazepam and nitrazepam

This study was designed to explore whether differences in the psychomotor, subjective and memory effects of different benzodiazepines (BDZ) relate to differences in their potencies. Two BDZs with similar kinetics but different potencies were compared. Flunitrazepam (0.5 and 1.0 mg), nitrazepam (5 and 10 mg) or placebo were administered to 50 healthy volunteers in a double-blind, parallel group designs. Subjects completed a test battery before and 1.5 h post-treatment. The higher dose of the more potent BDZ, flunitrazepam, impaired episodic memory in relation to placebo. In contrast, differences in psychomotor and subjective effects between BDZ were less clear. We conclude that a main caveat to the conclusion that potency plays a role in determining BDZ amnestic effects is the possible contribution of sedation and differential task sensitivities to apparent differential effects of BDZ compounds.