Effects of single dose of gamma-hydroxybutyric acid and lorazepam on psychomotor performance and subjective feelings in healthy volunteers

Objective: This study investigated the possible effects of gamma-hydroxybutyric acid (GHB) on human psychomotor performance and subjective feelings important for the safety of skilled performance. Methods: Twelve healthy volunteers, six males and six females, aged 22-36 years, participated as subjects. Drugs and placebo were administered according to a single-dose, double-blind, balanced, four-way, crossover design. Treatments were separated by a wash-out period of 1 week and consisted of placebo, lorazepam GHB 12.5 mg.kg(-1) and GHB 12.5 mg.kg(-1) and GHB 25 mg.kg(-1). Subjects' psychomotor performance was assessed at baseline and at 15, 60, 120 and 180 min after treatment. Mood was assessed using 16 visual analogue scales, before treatment and 120 min later. Psychomotor performance was measured using the following tests: Critical Flicker Fusion. Response Competition Test, Critical Tracking Task, Choice Reaction Time and Visual Vigilance Task. Results: GHB at both doses had no effects on attention, vigilance, alertness, short-term memory or psychomotor co-ordination (Delta-placebo, P > 0.05); calmness increased with the lower dose and contentedness decreased significantly at both doses (Delta-baseline, P < 0.05); adverse effects were limited to slight subjective feelings of dizziness and dullness, which disappeared 30-60 min after administration of the dose. Lorazepam caused impairment of psychometric functions. Conclusion: After single therapeutic doses, GHB does not induce changes in psychomotor performance and therefore the drug does not influence the ability to drive or work. However, repeated reports of the abuse potential of GHB and its usefulness in treating ethyl alcohol addiction indicate that it may play an "agonist-like" role, which means that it should only used under close medical supervision.