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Does oral alprazolam affect ventilation? A randomised, double-blind, placebo-controlled trial

Psychiatry Division, University Hospital Zürich, University of Zurich, Zurich, Switzerland

EW Russi

Pulmonary Division, University Hospital Zürich, Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland

S Buechi

Psychiatry Division, University Hospital Zürich, University of Zurich, Zurich, Switzerland

KE Bloch

Pulmonary Division, University Hospital Zürich, Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland

Abstract

The respiratory effects of benzodiazepines have been controversial. This investigation aimed to study the effects of oral alprazolam on ventilation. In a randomised, double-blind cross-over protocol, 20 healthy men ingested 1 mg of alprazolam or placebo in random order, 1 week apart. Ventilation was unobtrusively monitored by inductance plethysmography along with end-tidal PCO₂ and pulse oximetry 60–160 min after drug intake. Subjects were encouraged to keep their eyes open. Mean ± SD minute ventilation 120 min after alprazolam and placebo was similar (6.21 ± 0.71 vs 6.41 ± 1.12 L/min, P = NS). End-tidal PCO₂ and oxygen saturation did also not differ between treatments. However, coefficients of variation of minute ventilation after alprazolam exceeded those after placebo (43 ± 23% vs 31 ± 13%, P < 0.05). More encouragements to keep the eyes open were required after alprazolam than after placebo (5.2 ± 5.7 vs 1.3 ± 2.3 calls, P < 0.05). In a multiple regression analysis, higher coefficients of variation of minute ventilation after alprazolam were related to a greater number of calls. Oral alprazolam in a mildly sedative dose has no clinically relevant effect on ventilation in healthy, awake men. The increased variability of ventilation on alprazolam seems related to vigilance fluctuations rather than to a direct drug effect on ventilation.

Key Words: benzodiacepin • anxiolythic • ventilation • apnea • hypoventilation • control of breathing • anxiety

This version was published on May 1, 2009

Journal of Psychopharmacology, Vol. 23, No. 3, 322-327 (2009)
DOI: 10.1177/0269881108089875


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