The drug was sanctioned for pregnant women who haven't responded to other therapies, such as eating smaller meals, eating lower-fat foods and avoiding smells that can prompt nausea, the agency said in a media release.
Diclegis was evaluated in 261 adult women with morning sickness who had been pregnant between seven and 14 weeks. Women who took the drug had less nausea and vomiting than those who took a placebo. Studies also showed the drug didn't pose a threat to the fetus, the FDA said.
The most common side effect of the drug -- with a typical once-daily dose of two pills -- was potentially severe drowsiness. Women who take Diclegis should avoid driving or operating heavy machinery, the agency said.
The drug is marketed by the Canadian pharma firm Duchesnay, based in Quebec.
Medline Plus has more about morning sickness.