Study objectives: To determine the effect of the selective serotonin reuptake inhibitor citalopram on plasma levels of triazolam, and to determine the effect of a single dose of triazolam on steady-state levels of citalopram and its major metabolites.
Design: Open-label, multidose study.
Setting: Clinical Studies, Ltd., Fort Lauderdale, Florida.
Participants: Eighteen healthy male and female volunteers.
Interventions: Subjects received triazolam 0.25 mg alone and another 0.25-mg dose after 4 weeks of citalopram 20 mg/day for 1 week, followed by 3 weeks of citalopram 40 mg/day
Measurements and main results: Pharmacokinetic parameters were determined after single-dose administration of triazolam alone, after administration of citalopram alone at steady state, and after coadministration of the drugs. The pharmacokinetics of triazolam and its metabolite alpha-hydroxytriazolam were unchanged by citalopram coadministration. Triazolam appeared to be absorbed slightly more quickly during coadministration. Citalopram kinetics were unaffected by coadministration.
Conclusion: No pharmacokinetic interaction between the drugs was observed, suggesting that triazolam and other cytochrome P450 3A4 substrates can be coadministered safely with citalopram.