Pharmacokinetic comparison of oral solution and tablet formulations of citalopram: a single-dose, randomized, crossover study

Abstract

Background: Citalopram tablets fulfill most dosing needs in the treatment of depression, but some patients may have difficulty swallowing tablets and thus may be less likely to comply with their medication regimen. A liquid formulation of citalopram could be beneficial for such patients. Objective: This study was undertaken to compare the pharmacokinetic profiles of oral solution and tablet formulations of citalopram in healthy volunteers. Methods: In this open-label, single-dose, randomized, crossover, bioequivalence study, healthy volunteers alternately received one 60-mg dose of citalopram as an oral solution (10 mg/5 mL) and one 60-mg dose as a tablet. Doses were separated by a 14-day interval. Results: Of 24 subjects enrolled (mean age 27 years), 24 (16 men and 8 women) received the citalopram oral solution and 23 (15 men and 8 women) received the tablet; 1 subject discontinued before receiving the tablet. Citalopram was rapidly absorbed, with peak plasma concentrations occurring at ∼4 hours with both formulations. The rate and extent of absorption were similar between the 2 formulations, and no statistically significant differences were observed in half-life or oral clearance between formulations. Similarly, the pharmacokinetic profile for demethylcitalopram (the major metabolite of citalopram) did not differ between the 2 formulations. Both formulations were well tolerated, with no serious adverse events reported. Conclusion: The oral solution and tablet formulations of citalopram 60 mg were determined to be bioequivalent in this population.