Since griseofulvin is derived from a species of penicillin, the possibility of cross sensitivity with penicillin exists, however known penicillin sensitive patients have been treated without difficulty. Griseofulvin can potentiate an increase in hepatic enzymes that metabolize estrogens at an enhanced rate, including the estrogen component of oral contraceptives, thereby causing possible decreased contraceptive effects and menstrual irregularities. As griseofulvin may alter prothrombin activity in some patients, it is recommended that prothrombin times be determined at least 2 or 3 times a week with patients on anticoagulant therapy if griseofulvin is added to the regimen. Concomitant administration of phenobarbital and griseofulvin may result in reduced blood levels of griseofulvin due to the enzymatic acceleration of griseofulvin metabolism. During therapy with griseofulvin, patients should be advised to avoid exposure to intense natural or artificial sunlight.
Severe reactions occur infrequently.
Headache may occur, but usually disappears when the drug is taken with meals. Nausea, epigastric distress, heartburn, abdominal cramps, vomiting or diarrhea have been reported in a few patients. Chest pain, dryness of the mouth, breathlessness, arthralgia, neuritic pains, vertigo, and fever have also been reported. Allergic reactions, occurring rarely, include urticaria and angioneurotic edema, serum sickness, lupus erythematosus. Fatigue, lethargy, vertigo, decreased mental acuity, and secondary monilial skin infections have been reported as well as a few cases of photosensitivity.