May 23 2022

Classification of the active ingredient azithromycin

Risk level in pregnancy: This medicine is classified as Category B.

Studies in laboratory animals have not identified adverse fetal effects or impairment of fertility even at doses toxic.

Azithromycin crosses the placental barrier.

There have been several studies on the use of azithromycin in pregnancy, although few patients received this drug during the first trimester. A recent article includes more than 6000 children with birth defects identified in the records accumulated over a period of 14 years (1994-2008). Were not detected an association between consumption of macrolides and congenital malformations [1].

It have also been published several studies involving a small number of cases, although rarely demonstrative alone. In one of these, 11 pregnant took the drug during the first trimester, with normal term infants (there was an elective abortion) [2].

As with other medications, there are no adequate and well controlled studies in pregnant women, so that this medicine should only be used during pregnancy only if clearly needed it, since the lack of adverse effects in animal experimentation not excludes the potential risks in humans nor is an endorsement for use.


1: Lin KJ, Mitchell AA, Yau WP, Louik C, Hern?ndez-D?az S. Safety of macrolides during pregnancy. Am J Obstet Gynecol. 2013 Mar;208(3):221.e1-8.
2: Wilton LV, Pearce GL, Martin RM, Mackay FJ, Mann RD. The outcomes of pregnancy in women exposed to newly marketed drugs in general practice in England. Br J Obstet Gynaecol. 1998 Aug;105(8):882-9.

Update 18.07.2009

Meaning of category B

Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women OR Animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester.