Pharmacokinetic comparison of a delayed- release combination of doxylamine succinate and pyridoxine hydrochloride (diclectin®) and oral solutions of these drugs in healthy women of childbearing age

Background: The delayed-release combination of doxylamine succinate and pyridoxine hydrochloride was the most commonly used antiemetic (Bendectin) approved by FDA for nausea and vomiting of pregnancy (NVP) until its removal of the market in 1983. The drug is widely used today in Canada (Diclectin®). The pharmacokinetics of Diclectin® has never been described in humans. Objectives: To compare the pharmacokinetics of Diclectin® to oral solutions of its two components. Subjects and Methods: A randomized, cross over, open label design, comparing the pharmacokinetics of Diclectin® to those of the oral solutions of the two components in 18 healthy adult, non pregnant women of childbearing age. Results: Diclectin® exhibited similar oral bioavailability to those of the oral solutions. In contrast, the time-topeak, (Tmax), reflecting the rate of absorption, was 3-6 times longer for the two components of the delayed-release drug confirming its delayed-release characteristics. Conclusion: The pharmacokinetic profile of Diclectin® well explains its documented delayed efficacy.