The US Food and Drug Administration has approved new product labelling stating that atazanavir (Reyataz) should only be used with a booster dose of ritonavir in pregnant women.
Furthermore, women who are treatment-experienced, or taking tenofovir alongside atazanavir, should receive an increased dose of atazanavir (400/100mg) during the second and third trimesters of pregnancy, to compensate for possible changes in blood levels of the drug that may occur during this period.
The same applies if a woman is taking a H2-receptor antagonist during pregnancy. The FDA says that there are insufficient data to allow a recommendation on any further dose adjustment in the case of women taking both tenofovir and a H2-receptor antagonist alongside atazanavir, although it is known that H2-receptor antagonists also have the effect of reducing atazanavir levels, so particular caution is required.
H2-receptor antagonists are drugs used to block acid production in the stomach. They include products such as Zantac, Tagemet, Pepcid and Axid that may be taken to relieve acid reflux and severe stomach acid.
No atazanavir dose adjustment is required in the post-partum period.
Infants exposed to atazanavir in utero should be monitored for hyperbilirubinemia.
In the European Union it is recommended that a 300mg dose of atazanavir should always be boosted with ritonavir at a dose of 100mg. In the United States 400mg dose of atazanavir may be used without ritonavir boosting in patients new to treatment.
The labelling change follows the publication of data showing large variations in blood levels of atazanavir during pregnancy, particularly among women taking it with tenofovir.