USA. Bristol-Myers Squibb has issued a 'Dear Health-care Provider' letter advising of a change in the pregnancy category for efavirenz (Sustiva) from Category C (risk of fetal harm cannot be ruled out) to D (positive evidence of fetal risk), following four retrospective reports of neural tube defects (three cases of spina bifida cystica and one of Dandy Walker syndrome) in infants born to women who received efavirenz in their first trimester of pregnancy. Bristol-Myers Squibb warns that, prior to initiation of efavirenz (Sustiva), women of childbearing potential should undergo pregnancy testing. The company also recommends that women receiving efavirenz (Sustiva) should avoid pregnancy, and that efavirenz (Sustiva) should be used during the first trimester only "if the potential benefit justifies the potential risk to the fetus".

Reference:

'Dear Health-care Provider' letter from Bristol-Myers Squibb Company, March 2005 (http://www.fda.gov).