penicillin G benzathine (Bicillin L-A)

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical and Pharmacy Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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.

Penicillin G benzathine may decrease the effectiveness of oral contraceptives (birth control pills). Patients may need to use a backup method of contraceptive while on antibiotic treatment.

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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