ObjectiveSolifenacin succinate (YM905; Vesicare®) is a promising new bladder selective muscarinic receptor antagonist under investigation for the treatment of overactive bladder. This study was designed to assess the absolute bioavailability of a single oral dose of solifenacin 10mg, which is twice the suggested starting dose.Study designSingle-centre, open-label, randomised, two-period, crossover, single-dose study.MethodsSolifenacin was administered orally as a 10mg dose and intravenously as a 5mg dose. Oral and intravenous (IV) doses were divided by a washout period of ≥14 days.Study participantsThe study group consisted of 12 healthy young men, aged 20−45 years, nine of whom completed the study.ResultsThe pharmacokinetic analysis comprised nine subjects. A single oral dose of solifenacin 10mg had a high absolute bioavailability of 88.0% (95% confidence interval 75.8, 102.1), low clearance (9.39 L/h [SD 2.68]), and an extensive mean volume of distribution at steady state (599L [SD 86]). Only 7% of solifenacin was excreted intact in the urine. Single oral and IV administration of solifenacin was well tolerated in this study. The most common adverse events related to drug treatment were headache and somnolence.ConclusionsPharmacokinetic analyses of single oral and IV doses of solifenacin demonstrated that the drug has a high absolute oral availability of 88%. This finding suggests that solifenacin may have a higher and less variable bioavailability than other antimuscarinic agents.