Griseofulvin

Pronunciation: griss-ee-oh-FULL-vin
Class: Antifungal Microsize

Trade Names

Grifulvin V
- Tablets 500 mg (as microsize)

Ultramicrosize

Gris-PEG
- Tablets 125 mg (as ultramicrosize)
- Tablets 250 mg (as ultramicrosize)

Pharmacology

Deposited preferentially into infected skin, which gradually sloughs off and is replaced by noninfected tissue; binds tightly to new keratin, which becomes highly resistant to fungal invasions.

Pharmacokinetics

Absorption

C max is 0.5 to 1.5 mcg/mL. T max is about 4 h.

Food

A high-fat meal may increase C max . Microsize is 25% to 70% absorbed. Ultramicrosize is about 100% absorbed.

Distribution

Mainly deposited in the keratin layer of skin, hair, and nails.

Metabolism

Hepatic. Major metabolites are 6-methyl-griseofulvin and its glucuronide conjugate.

Elimination

The t ½ is about 24 h. Primarily renal excretion. About 36% is excreted unchanged in the feces.

Indications and Usage

Treatment of ringworm infections of skin, hair, and nails caused by susceptible fungi.

Contraindications

Porphyria; hepatic disease.

Dosage and Administration

Adults

PO 500 to 1,000 mg microsize (330 to 750 mg ultramicrosize) in single or divided doses. May need to give for several weeks.

Children

PO 11 mg microsize/kg/day (125 to 500 mg) or 7.3 mg ultramicrosize/kg/day (82.5 to 330 mg).

General Advice

  • Administer with or after meals, particularly with fatty foods if not contraindicated.
  • Generally administered in conjunction with topical agent.
  • Do not interchange griseofulvin microsize with ultramicrosize because dosage is different.

Storage/Stability

Store between 36° to 86°F.

Drug Interactions

Alcohol

Effects of alcohol may be potentiated with tachycardia and flushing.

Anticoagulants

Anticoagulant effect may be decreased.

Barbiturates

May depress griseofulvin serum levels.

Contraceptives, oral

May cause loss of contraceptive effectiveness.

Laboratory Test Interactions

False elevation of vanillylmandelic acid test assayed by photometric tests but not with gas or thin layer chromatography method.

Adverse Reactions

CNS

Headache; fatigue; dizziness; insomnia; confusion; paresthesias.

Dermatologic

Rash; urticaria.

EENT

Oral thrush.

GI

Nausea; vomiting; epigastric distress; diarrhea; GI bleeding.

Genitourinary

Proteinuria.

Hematologic

Leukopenia; granulocytopenia.

Hepatic

Hepatic toxicity.

Metabolic

Interferes with porphyrin metabolism.

Miscellaneous

Angioneurotic edema.

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Hypersensitivity

Drug may need to be discontinued. Also, penicillin cross-sensitivity is possible, although some penicillin-sensitive patients have used without difficulty.

Lupus

May exacerbate lupus or lupus-like syndrome.

Patient Information

  • Advise patient to inspect skin for signs of improvement of infection or reinfection.
  • Explain importance of good hygiene, particularly to affected areas.
  • Inform patient that beneficial effects of drug may not be observable for weeks to months.
  • Instruct patient to report these symptoms to health care provider: fever, sore throat, skin rash.
  • Caution patient to avoid intake of alcoholic beverages or other CNS depressants.
  • Advise patient that drug may cause dizziness and to use caution while driving or performing other tasks requiring mental alertness.
  • Caution patient to avoid exposure to sunlight and to use sunscreen or wear protective clothing to avoid photosensitivity reaction.

Copyright © 2009 Wolters Kluwer Health.

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