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Penicillin VK Side Effects

Generic Name: penicillin v potassium

Note: This page contains side effects data for the generic drug penicillin v potassium. It is possible that some of the dosage forms included below may not apply to the brand name Penicillin VK.

For the Consumer

Applies to penicillin v potassium: capsule, powder for solution, powder for suspension, solution, suspension, syrup, tablet, tablet for suspension, tablet chewable, tablet extended release

As well as its needed effects, penicillin v potassium (the active ingredient contained in Penicillin VK) may cause unwanted side effects that require medical attention.

Stop taking penicillin v potassium and get emergency help immediately if any of the following effects occur:

Less common:
  • Fast or irregular breathing
  • fever
  • joint pain
  • lightheadedness or fainting (sudden)
  • puffiness or swelling around the face
  • red, scaly skin
  • shortness of breath
  • skin rash, hives, itching

Major Side Effects

If any of the following side effects occur while taking penicillin v potassium, check with your doctor immediately:

  • Abdominal or stomach cramps and pain (severe)
  • abdominal tenderness
  • convulsions (seizures)
  • decreased amount of urine
  • diarrhea (watery and severe), which may also be bloody
  • mental depression
  • nausea and vomiting
  • pain at place of injection
  • sore throat and fever
  • unusual bleeding or bruising
  • yellow eyes or skin
Rare - For penicillin G procaine only
  • Agitation or combativeness
  • anxiety
  • confusion
  • fear of impending death
  • feeling, hearing, or seeing things that are not real

Minor Side Effects

Some penicillin v potassium side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common:
  • Diarrhea (mild)
  • headache
  • sore mouth or tongue
  • vaginal itching and discharge
  • white patches in the mouth and/or on the tongue

For Healthcare Professionals

Applies to penicillin v potassium: oral powder for reconstitution, oral tablet


In general, side effects associated with oral penicillin therapy have been reported much less frequently than with parenteral penicillin therapy. However, all degrees of hypersensitivity, including fatal anaphylaxis, have been reported with oral penicillin.[Ref]


Gastrointestinal side effects have included nausea, vomiting, epigastric distress, diarrhea, and black hairy tongue. Clostridium difficile associated diarrhea has been reported and may occur during or after therapy. Pancreatitis, intestinal necrosis, and blood in the stool have also been reported.[Ref]


Hypersensitivity reactions with penicillin are more common and more serious with intravenous therapy, but have also been reported with oral therapy. An initial sensitizing exposure is required to stimulate the production of antigen-specific IgE before clinical manifestations of hypersensitivity are seen on the second exposure. There are numerous "hidden" environmental or occupational exposures to penicillin including in utero exposure, breast milk exposure, and occupational exposure.[Ref]

Hypersensitivity side effects have included skin eruptions (maculopapular to exfoliative dermatitis), pruritus, urticaria, laryngeal edema, fever, eosinophilia, hypersensitivity myocarditis, serum sickness-like reactions (chills, fever, edema, arthralgia, and prostration), severe or fatal anaphylaxis, shock, and death.[Ref]


Dermatologic side effects have included rash, peeling, mucosal ulceration, and urticaria.


Hematologic side effects have included hemolytic anemia, anemia, leukopenia, thrombocytopenia, and lymphadenopathy.


Hepatic side effects have included increased SGOT, reversible hepatotoxicity, jaundice, and prolonged cholestasis.

Nervous system

Nervous system side effects have included severe reactions with high dose penicillin therapy or in patients with renal dysfunction. These reactions have included myoclonus, seizures, auditory and visual hallucinations, and decreased mentation. Neurologic reactions occurred frequently in patients with renal dysfunction. Aseptic meningitis has been reported.

Severe neurologic reactions were most often seen with penicillin doses of 18 million to 80 million units daily. These reactions frequently abated after discontinuation of penicillin. In several cases, penicillin was restarted at a lower dose with no further sequelae. In one review, the authors found that cerebral spinal fluid (CSF) penicillin levels were higher in patients with seizures than in those without. CSF penicillin levels ranged from 12 to 61 units/mL in the seizure group with the highest CSF concentrations, compared to 7.8 units/mL in the group without seizures.


Other side effects have included fatigue, asthenia, pain, abnormal taste perception, tinnitus, and aggravation of existing disorders.


Respiratory side effects have included hypoxia, apnea, and dyspnea.


1. "Product Information. Veetids (penicillin)." Apothecon Inc, Plainsboro, NJ.

It is possible that some side effects of Penicillin VK may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

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