Generic name: Griseofulvin.

Other brand names: Fulvicin P/G, Fulvicin U/F, Grifulvin V, Grisactin.

Gris-PEG is an antifungal. It destroys and prevents the growth of fungi. 

Quick Facts About Gris-PEG


Used to treat ringworm infections, including: athlete’s foot, and ringworm of the body, groin and thigh, nails, and scalp.

Gris-PEG Dosage

Take with food or whole milk to avoid stomach irritation and assist your body in absorbing this medication. Inform your doctor if you are on a low-fat diet Practice good oral hygiene to prevent and control infection. May observe relief in a few days; must take for an extended period.

  • Usual adult dose: for ringworm of the body, groin, thigh, and scalp — 375 milligrams per day as a single dose or divided into smaller doses. For athlete’s foot and ringworm of the nails — 750 milligrams per day divided into smaller doses. Treatment periods — ringworm of the scalp: 4 to 6 weeks; ringworm of the body: 2 to 4 weeks; ringworm of the fingernails: 4 months; ringworm of the toenails: 6 months; and athlete’s foot: 4 to 8 weeks.
  • Usual child dose: for ringworm of the scalp — 3.3 milligrams per pound of body weight per day in a single dose. Not prescribed for children 2 years and under.
  • Missed dose: take as soon as possible, unless almost time for next dose. In that case, do not take missed dose; go back to regular schedule. Do not double doses.

Gris-PEG Side Effects

Overdose symptoms:

no specific information available. If you suspect an overdose, immediately seek medical attention.

More common side effects: hives, skin rashes.

Less common Gris-PEG side effects: confusion, diarrhea, dizziness, fatigue, headache, impairment of performance of daily routine, inability to fall or stay asleep, nausea, oral thrush (mouth inflammation), upper abdominal pain, vomiting. Rare side effects: swelling and itching of areas of skin, tingling sensation in hands and feet.


Inform your doctor before combining Gris-PEG with:

blood thinners such as Coumadin, barbiturates such as phenobarbital, oral contraceptives. May decrease effectiveness of birth control pills.

Use alcohol with caution, may cause fast heartbeat and flushed skin; Gris-PEG may intensify the effects of alcohol.

Special Cautions

Do not take if pregnant If you become pregnant during Gris-PEG therapy, immediately contact your doctor; is potentially hazardous to the fetus. Consult with your doctor if breastfeeding.

No special precautions apply to seniors.

Follow doctor’s instructions carefully for children. Not prescribed for children 2 years and under.

  • Do not take if you have liver damage or porphyria.
  • Should not take if sensitive to or allergic to this or similar medications, or penicillin.
  • Minimize exposure to intense natural or artificial sunlight.
  • If you develop lupus erythematosus or a lupus-like condition (arthritis, red butterfly rash over the nose and cheeks, tiredness, weakness, sensitivity to sunlight, skin eruptions), immediately contact your doctor.
  • Doctor should monitor kidneys, liver, and blood cell production if taking this medication over an extended period.
  • Gris-PEG does not prevent fungal infections.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Gris-PEG side effects, please contact your healthcare provider.