Do not use this medication if you are allergic to penicillin V or to any other penicillin antibiotic, such as amoxicillin (Amoxil), ampicillin (Omnipen, Principen), carbenicillin (Geocillin), dicloxacillin (Dycill, Dynapen), or oxacillin (Bactocill).
Before using penicillin V, tell your doctor if you are allergic to cephalosporins such as Ceclor, Ceftin, Duricef, Keflex, and others, or if you have asthma, kidney disease, a bleeding or blood clotting disorder, a history of diarrhea caused by taking antibiotics, or a history of any type of allergy.
Penicillin V can make birth control pills less effective, which may result in pregnancy. Before taking this medicine, tell your doctor if you use birth control pills. Take penicillin V for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated. Penicillin V will not treat a viral infection such as the common cold or flu. Do not give this medication to another person, even if they have the same symptoms you do.
Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or has blood in it, call your doctor. Do not use any medicine to stop the diarrhea unless your doctor has told you to.
Before taking this medicine
Do not use this medication if you are allergic to penicillin V or to any other penicillin antibiotic, such as:
amoxicillin (Amoxil, Amoxicot, Biomox, Dispermox, Trimox);
ampicillin (Omnipen, Principen);
carbenicillin (Geocillin);
dicloxacillin (Dycill, Dynapen); or
oxacillin (Bactocill).
Before using penicillin V, tell your doctor if you are allergic to any drugs (especially cephalosporins such as Ceclor, Ceftin, Duricef, Keflex, and others), or if you have:
asthma;
kidney disease;
a bleeding or blood clotting disorder;
a history of diarrhea caused by taking antibiotics; or
a history of any type of allergy.
If you have any of these conditions, you may need a dose adjustment or special tests to safely take penicillin V.
FDA pregnancy category B. Penicillin V is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment. Penicillin V can make birth control pills less effective, which may result in pregnancy. Before taking this medicine, tell your doctor if you use birth control pills. Penicillin V can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.
 Penicillin v potassium pregnancy and breastfeeding warnings (more detail)
