DRUG INTERACTIONS: Penicillin G benzathine may decrease the renal tubular secretion (elimination via the kidneys) of methotrexate (Trexall, Rheumatrex) causing an increase in blood levels of methotrexate. Patients on combination therapy should be closely monitored for the occurrence of side effects.
Penicillin G benzathine may interfere with the body's response to the live typhoid vaccine (Vivotif Berna Vaccine). The general recommendation is to wait 24 hours or longer since the administration of the last dose of the antibiotic before administrating the vaccine.
Coadminstration of penicillin G benzathine with warfarin (Coumadin) may increase the risk of bleeding. Antibiotics may inhibit vitamin K synthesis and warfarin is a vitamin K antagonist (also inhibits the action of vitamin K). Patients on combination therapy should be closely monitored for signs or symptoms of bleeding.
PREGNANCY: Penicillin G benzathine has not been adequately evaluated in pregnant women. No evidence of harm has been demonstrated in animal reproduction studies. Use of penicillin products has generally not caused fetal harm when used during pregnancy. Penicillin G is the drug of choice for the treatment of syphilis during pregnancy. Penicillin G benzathine is classified as FDA pregnancy risk 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).
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