Bioavailability of Cariban^® Capsules: A Modified-Release Fixed-Dose Combination of Doxylamine and Pyridoxine to Relieve Nausea and Vomiting During Pregnancy

Background: Nausea and vomiting is a very prevalent condition during pregnancy. Combination of doxylamine and pyridoxine is placed as first-line pharmacological option for its treatment in most clinical guidelines. Among different release forms available, Cariban^® is a fixed-dose combination of doxylamine/pyridoxine 10/10 mg, formulated as modified-release capsules.

Objectives: In the present study, we aimed to characterize the bioavailability performance of Cariban^® in vitro and in vivo.

Methods: An in vitro dissolution test was performed to evaluate the release profile of Cariban^®, together with immediate- and delayed-release formulations available on the market. A single-center, single-dose, open-label bioavailability study following Cariban^® administration in 12 healthy adult female patients was carried out to explore the drug behavior in vivo (protocol NBR-002-13; EUDRA-CT 2013-005422-35). These data were additionally used to perform a computational pharmacokinetic simulation of the posology approved for this drug.

Results: Cariban^® capsules demonstrate a prolonged-release performance, with an early, gradual, and progressive release of both actives until reaching a complete dissolution after 4-5 h in solution. The pharmacokinetic features of these capsules show that doxylamine and pyridoxine metabolites are early absorbed, being all detectable in plasma within 1 h following oral administration. Computational pharmacokinetic simulation predicts that different posology provides distinct profiles of metabolites in plasma, with 1-1-2 (morning-midafternoon-night) being the one that concentrates higher plasma levels but lower dose dumping for 24 h.

Conclusion: Cariban^® behaves as a prolonged-release formulation, which correlates with rapid absorption and arising of the actives in the plasma, but also long-lasting and sustained bioavailability, especially when administered following the complete posology. These results would underlie its demonstrated efficacy to relieve nausea and vomiting of pregnancy (NVP) under clinical settings.