DRUG INTERACTIONS: Penicillin V potassium may inhibit the renal tubular secretion (elimination of the drug via the kidneys) of methotrexate (Trexall, Rheumatrex). Co-administration may result in higher blood levels of methotrexate and increases the risk of methotrexate toxicity (side effects).
Penicillin V potassium may interfere with the effectiveness of the live typhoid vaccine. Administration of the vaccine must be separated by at least 24 hours from the last dose of the antibiotic.
Antibiotics such as penicillin V potassium may decrease the effectiveness of certain oral contraceptives or birth control pills. Patients may use an alternative form of birth control (for example, condoms) while on antibiotic therapy to prevent unexpected pregnancies.
Penicillin antibiotics may inhibit vitamin K synthesis due to their effect on the normal intestinal flora. Therefore, co-administration of warfarin (a vitamin K antagonist) with penicillin V potassium may increase the risk of bleeding.
PREGNANCY: Penicillin V potassium 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). Use of penicillin products in humans has not shown any evidence of fetal harm. Additionally, no evidence of fetal harm has been reported in animal studies. However, there is a lack of adequate and well controlled studies in pregnant women. As with all medications, use of penicillin V potassium during pregnancy requires careful evaluation of treatment benefits and potential risk to the fetus.
NURSING MOTHERS: Penicillin V potassium is excreted in breast milk. Penicillin products have been reported to cause diarrhea, candidiasis (fungal infections), and skin rash in breast feed babies. Due to the lack of safety data, this medication should be used cautiously in females who are breastfeeding. Penicillin type antibiotics are used for treating infection in children.
REFERENCE: FDA Prescribing Information.
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