Observational studies of inadvertent exposure during early pregnancy or treatment when no alternatives are available remain the methods of determining drug safety. The antihistamine component, like other antihistamines, sometimes causes drowsiness and anticholinergic signs and symptoms. 7,8 although many fewer pregnant patients have been studied with these drugs. These medications offer the advantage of oral, rectal, and parenteral routes of administration with formulations allowing for more acute relief, especially for women with HG, but they might be sedating, and phenothiazines might have extrapyramidal effects as well. Corticosteroids have not demonstrated serious teratogenic potential in humans.
Efficacy is as important as safety, but evidence-based information is relatively scant.
Only doxylamine and pyridoxine was shown to be effective compared with placebo in more than 2000 patients. Pyridoxine alone might be effective, at least when contained within a multivitamin. Therapies with limited data on their safety should be tried only if other approaches have failed and only after discussion of the uncertainties with patients. Ideally, such patients should be enrolled in studies. Treatment of nausea and vomiting not caused by NVP or HG should be directed toward underlying disease.