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Penicillin V potassium

Brand names: Penicillin VK

Penicillin V potassium is a penicillin antibiotic used mainly for strep throat and some dental infections.

Brand namesPenicillin VK
Type of medicinePenicillin antibiotic
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It's one of the oldest antibiotics and still a first choice for strep throat.

What it's used for

  • Strep throat
  • Scarlet fever
  • Some dental infections
  • Preventing rheumatic fever from coming back

How to take it

  • Take it on an empty stomach, 1 hour before or 2 hours after a meal.
  • Space doses evenly and finish the full course.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Nausea
  • Diarrhea
  • Black hairy tongue (harmless)
Call 911Swelling of the face, lips, or throat, hives, or trouble breathing
Call 911A blistering, peeling, or widespread red rash, especially with fever
Call your provider todaySevere watery or bloody diarrhea, even weeks after finishing (possible C. diff infection)

Warnings

  • Don't take it if you're allergic to penicillin. Tell your provider about any past reaction to antibiotics.

Other medicines, foods, and alcohol

  • Probenecid raises penicillin levels.
  • It can raise methotrexate levels.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Commonly used in pregnancy when needed.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember. If it's almost time for the next dose, skip the missed one. Don't double up, and still finish the full course.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.