The safety of higher-than-standard dose of doxylamine/pyridoxine for nausea/vomiting of pregnancy

A delayed-release combination of doxylamine/pyridoxine (D/P), is the only approved antiemetic medication for use in pregnancy in Canada. The standard recommended dose is up to 4 tablets a day, regardless of body weight. Our objective was to determine the incidence of adverse effects and pregnancy outcome in 225 women taking D/P. Design: Observational, prospective study. Results: One third (33.6%) of women reported having side effects (sleepiness, tiredness and/or drowsiness) from the medication. There was no association between the dose per kg and risk of adverse effects. Maximum D/P dose ranged from 0.1 mg/kg to 2.0 mg/kg (1-12 tabs). NVP was reported as severe by the majority (75.8%) of women. Mean birth weight (BW) was 3400g and gestational age (GA) 39 weeks. Multivariate analysis revealed that only pre-pregnancy weight and GA predicted lower BW, not the dose of D/P. There were only two newborns with major malformation, consistent with population risk. Conclusion: A higher than standard dose of D/P when calculated per kg of body weight, does not affect either the incidence of adverse effects of the medication, or the pregnancy outcome. If needed, D/P can be given as more than 4 tabs/day to normal-ize for body weight.