The question concerns a woman, pregnant in week 16-17, who needs to be treated for a Giardia lambli

Fråga: The question concerns a woman, pregnant in week 16-17, who needs to be treated for a Giardia lamblia infection. The treatment would consist of either metronidazole 250 mg x3 for 5 days, or tinidazole 2g as a single-dose treatment. Is there any preference with respect to the fetus?

Sammanfattning: Both drugs may be safely used in this patient. Treatment with metronidazole may be preferred, since there is more available documentation concerning its use in pregnancy and the drug is considered to be safe during the second and third trimester. This should be weighted against the advantage that tinidazole may be administered as a single-dose.

Svar: The question concerning the use of metronidazole during pregnancy has been dealt with extensively in earlier Drugline documents. In summary, a low-dose treatment course (up to 1000 mg/day) may be considered safe during the second and third trimesters (1). Treatment during the first trimester is considered more controversial as the available reports have conflicting conclusions concerning the possibility of teratogenic effects (2).

There are no cases reported concerning any teratogenic effects caused by tinidazole (3). The experience on the use of tinidazole during pregnancy seems very limited. A Medline search back to 1980 did not reveal any studies concerning the safety of tinidazole during pregnancy. Metronidazole and tinidazole belong to the same group of nitro-imidazole derivatives. According to (4), the drug is expected to have the same side effects as metronidazole.