Gamma-hydroxybutyrate and ethanol effects and interactions in humans.

Background: Gamma-hydroxybutyrate (GHB) is a common drug of abuse that can produce serious toxicity, particularly when used with other sedatives. We examined the individual and combined effects of GHB and ethanol in human volunteers.
Methods: Sixteen healthy adults (7 men) were given 50 mg/kg GHB (Xyrem), 0.6 g/kg ethanol in 2 doses, alone and combined in a double-blind, placebo-controlled, crossover study. Plasma concentrations, heart rate (HR), blood pressure (BP), and oxygen saturation (O2sat) were serially monitored for 24 hours.
Results: Adverse events included 2 instances of hypotension and 6 episodes of vomiting with GHB-plus-ethanol ingestion. Oxygen saturation was decreased by GHB and ethanol individually, and maximally decreased by the drugs combined (max -2.1% +/- 0.3%, P < 0.0001 vs placebo). Compared with baseline, systolic and diastolic BP were significantly decreased, and HR was increased by ethanol but not affected by GHB alone (maximum systolic BP change -15.7 +/- 3.0 mm Hg, P = 0.0006; maximum HR change 13.5 +/- 2.3 beats per minute, P = 0.006). Ethanol coingestion resulted in 16% higher GHB maximal plasma concentration and 29% longer elimination half-life, indicating possible enhanced bioavailability or reduced clearance of GHB caused by ethanol, however, these effects were not statistically significant.
Conclusions: Modest doses of GHB do not affect hemodynamic function, but O2sat was decreased. Gamma-hydroxybutyrate-plus-ethanol resulted in more adverse effects, including gastrointestinal disturbances, hypotension, and decreased O2sat, but only minimal pharmacokinetic interactions were observed.