Drug Interactions between sulfadoxine and Vivotif

According to the prescribing information for live, attenuated oral typhoid vaccine, chemoprophylactic doses of the antimalarials chloroquine, mefloquine, and pyrimethamine-sulfadoxine may be given concomitantly with the vaccine. Previously, there had been concerns that these agents may interfere with the immunogenicity of the vaccine based on in vitro data demonstrating antibacterial activity against the vaccine strain of Salmonella typhi (Ty21a), which could prevent a sufficient degree of multiplication to occur in order to induce a protective immune response. This led to recommendations to complete the vaccination at least 3 days before the first dose of antimalarial or delaying vaccination until at least 3 days after completion of antimalarial prophylaxis. However, it has been shown that concomitant administration of chloroquine (500 mg at weekly intervals; n=30), mefloquine (250 mg at weekly intervals; n=30), and pyrimethamine-sulfadoxine at chemoprophylactic doses did not affect the immune response to the vaccine or compromise its efficacy in healthy adult subjects. In these studies, the antimalarials were given first, followed 12 hours later by the vaccine.