Gris-Peg

Systemic Dermatological Antifungals

Bioavailability varies between microsize and ultramicrosize formulations as well as manufacturers (see Pharmacokinetics).

Ultramicrosize griseofulvin tablets:
Administer orally with a fatty meal to increase absorption.
Tablets can be swallowed whole or crushed and sprinkled onto 1 tablespoonful of applesauce and swallowed immediately without chewing.
Microsize griseofulvin tablets:
Administer orally with a fatty meal to increase absorption.

Microsize griseofulvin suspension:
Administer orally with a fatty meal to increase absorption.
Shake the suspension well prior to administration.

Stevens-Johnson syndrome / Delayed / Incidence not known
lupus-like symptoms / Delayed / Incidence not known
toxic epidermal necrolysis / Delayed / Incidence not known
angioedema / Rapid / Incidence not known
erythema multiforme / Delayed / Incidence not known
GI bleeding / Delayed / Incidence not known
coagulopathy / Delayed / Incidence not known
proteinuria / Delayed / Incidence not known
teratogenesis / Delayed / Incidence not known

peripheral neuropathy / Delayed / Incidence not known
confusion / Early / Incidence not known
candidiasis / Delayed / Incidence not known
elevated hepatic enzymes / Delayed / Incidence not known
hepatitis / Delayed / Incidence not known
hyperbilirubinemia / Delayed / Incidence not known
jaundice / Delayed / Incidence not known
leukopenia / Delayed / Incidence not known
neutropenia / Delayed / Incidence not known

dizziness / Early / Incidence not known
headache / Early / Incidence not known
insomnia / Early / Incidence not known
fatigue / Early / Incidence not known
paresthesias / Delayed / Incidence not known
diarrhea / Early / Incidence not known
abdominal pain / Early / Incidence not known
vomiting / Early / Incidence not known
nausea / Early / Incidence not known
rash / Early / Incidence not known
photosensitivity / Delayed / Incidence not known
urticaria / Rapid / Incidence not known

Fulvicin P/G, Fulvicin U/F, Grifulvin V, Gris-Peg, Grisactin

Rx

Oral antifungal antibiotic produced by certain species of Penicillium. Marketed in several formulations to increase bioavailability and decrease GI intolerance. Used for tinea and other fungal infections, including onychomycosis.NOTE: On April 10, 2007, Ortho-McNeil and the FDA informed of a nationwide recall of griseofulvin oral suspension, due to 2 reports of glass fragments found in bottles of this liquid. The recall is limited to this liquid formulation (roughly 100 lots) from this manufacturer and does not include any other dosage form. The voluntary recall is being conducted by Ortho Dermatological, Division of Ortho-McNeil Pharmaceutical, Inc., manufacturer of GRIFULVIN V® and also of griseofulvin oral suspension under the Patriot Pharmaceuticals, L.L.C., label. Consumers should contact their pharmacy to see if they have the product that has been recalled. It is not clear that the recall will cause any shortages.

500 mg PO once daily or divided 2 to 4 times daily until organism is completely eradicated.

20 to 25 mg/kg/day (Max: 500 mg/day) PO divided twice daily. Continue treatment until organism is completely eradicated. The FDA-approved labeling states that 10 mg/kg/day PO is usually an effective dose and recommends that children weighing 14 kg to 23 kg receive 125 to 250 mg/day PO and that children weighing more than 23 kg receive 250 to 500 mg/day PO in divided doses.

375 mg PO given either once daily or divided 3 times daily until organism is completely eradicated.

10 to 15 mg/kg/dose (Max: 375 mg/dose) PO once daily. Continue treatment until organism is completely eradicated. The FDA-approved labeling states that 7.3 mg/kg/day PO is usually an effective dose and recommends that children weighing 16 kg to 27 kg receive 125 to 187.5 mg/day PO and that children weighing more than 27 kg receive 187.5 to 375 mg/day PO.

750 to 1,000 mg PO once daily or divided 2 to 4 times daily for 4 to 8 weeks or until organism is completely eradicated.

20 to 25 mg/kg/day (Max: 1 g/day) PO divided twice daily. Treat for 4 to 8 weeks or until organism is completely eradicated. The FDA-approved labeling states that 10 mg/kg/day PO is usually an effective dose and recommends that children weighing 14 to 23 kg receive 125 to 250 mg/day PO and that children weighing more than 23 kg receive 250 to 500 mg/day PO in divided doses.

750 mg PO once daily or divided 2 to 3 times daily for 4 to 8 weeks or until organism is completely eradicated.

10 to 15 mg/kg/dose (Max: 750 mg/dose) PO once daily. Treat for 4 to 8 weeks or until organism is completely eradicated. The FDA-approved labeling states that 7.3 mg/kg/day PO is usually an effective dose and recommends that children weighing 16 kg to 27 kg receive 125 to 187.5 mg/day PO and that children weighing more than 27 kg receive 187.5 to 375 mg/day PO.

500 mg PO once daily or divided 2 to 4 times daily for at least 6 weeks or until organism is completely eradicated.

20 to 25 mg/kg/day (Max: 500 mg/day) PO divided twice daily for at least 6 weeks or until organism is completely eradicated. The FDA-approved labeling dose is 10 mg/kg/day PO and 125 to 250 mg/day PO or 250 to 500 mg/day PO in divided doses for children weighing 14 to 23 kg or more than 23 kg, respectively.

375 mg PO once daily or divided 3 times daily for at least 6 weeks or until organism is completely eradicated.

10 to 15 mg/kg/dose (Max: 375 mg/dose) PO once daily for at least 6 weeks or until organism is completely eradicated. The FDA-approved dose is 7.3 mg/kg/day PO and 125 to 187.5 mg/day PO or 187.5 to 375 mg/day PO for children weighing 16 to 27 kg or more than 27 kg, respectively.

500 mg PO once daily or divided 2 to 4 times daily for 2 to 4 weeks or until organism is completely eradicated.

20 to 25 mg/kg/day (Max: 500 mg/day) PO divided twice daily. Treat for 2 to 4 weeks or until organism is completely eradicated. The FDA-approved labeling states that 10 mg/kg/day PO is usually an effective dose and recommends that children weighing 14 kg to 23 kg receive 125 to 250 mg/day PO and that children weighing more than 23 kg receive 250 to 500 mg/day PO in divided doses.

375 mg PO once daily or divided 3 times daily for 2 to 4 weeks or until organism is completely eradicated.

10 to 15 mg/kg/dose (Max: 375 mg/dose) PO once daily. Treat for 2 to 4 weeks or until organism is completely eradicated. The FDA-approved labeling states that 7.3 mg/kg/day PO is usually an effective dose and recommends that children weighing 16 kg to 27 kg receive 125 to 187.5 mg/day PO and that children weighing more than 27 kg receive 187.5 to 375 mg/day PO.

750 to 1,000 mg PO once daily or divided 2 to 4 times daily for at least 4 months, depending on growth rate.

20 to 25 mg/kg/day (Max: 1 g/day) PO divided twice daily. Treat for at least 4 months, depending on growth rate. The FDA-approved labeling states that 10 mg/kg/day PO is usually an effective dose and recommends that children weighing 14 to 23 kg receive 125 to 250 mg/day PO and that children weighing more than 23 kg receive 250 to 500 mg/day PO in divided doses.

750 mg PO once daily or divided 2 to 3 times daily for at least 4 months, depending on growth rate.

10 to 15 mg/kg/dose (Max: 750 mg/dose) PO once daily. Treat for at least 4 months, depending on growth rate. The FDA-approved labeling states that 7.3 mg/kg/day PO is usually an effective dose and recommends that children weighing 16 kg to 27 kg receive 125 to 187.5 mg/day PO and that children weighing more than 27 kg receive 187.5 to 375 mg/day PO.

750 to 1,000 mg PO once daily or divided 2 to 4 times daily for at least 6 months, depending on growth rate.

20 to 25 mg/kg/day (Max: 1 g/day) PO divided twice daily. Treat for at least 6 months, depending on growth rate. The FDA-approved labeling states that 10 mg/kg/day PO is usually an effective dose and recommends that children weighing 14 to 23 kg receive 125 to 250 mg/day PO and that children weighing more than 23 kg receive 250 to 500 mg/day PO in divided doses.

750 mg PO once daily or divided 2 to 3 times daily for at least 6 months, depending on growth rate.

10 to 15 mg/kg/dose (Max: 750 mg/dose) PO once daily. Treat for at least 6 months, depending on growth rate. The FDA-approved labeling states that 7.3 mg/kg/day PO is usually an effective dose and recommends that children weighing 16 kg to 27 kg receive 125 to 187.5 mg/day PO and that children weighing more than 27 kg receive 187.5 to 375 mg/day PO.

Specific dosage adjustments in hepatic impairment are not available. Griseofulvin does undergo hepatic metabolism; therefore, use with caution in patients with hepatic impairment. Griseofulvin is contraindicated in hepatocellular failure.

No dosage adjustment needed.

Acetaminophen; Aspirin, ASA; Caffeine: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Acetaminophen; Aspirin: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Acetaminophen; Aspirin; Diphenhydramine: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Albuterol; Budesonide: (Moderate) Theoretically, induction of the cytochrome P450 3A4 isoenzyme by griseofulvin may result in a lowering of budesonide plasma concentrations, reducing the clinical effect.
Aminosalicylate sodium, Aminosalicylic acid: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Butalbital; Caffeine: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Caffeine: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Caffeine; Orphenadrine: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Carisoprodol: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Carisoprodol; Codeine: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Citric Acid; Sodium Bicarbonate: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Dipyridamole: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Omeprazole: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Aspirin, ASA; Oxycodone: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Barbiturates: (Minor) Barbiturates can impair the oral absorption of griseofulvin, resulting in decreased serum concentrations and, potentially, decreased antifungal efficacy. The clinical significance of this interaction is uncertain, but the manufacturer recommends that these drugs not be co-administered.
Benzoic Acid; Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Bismuth Subsalicylate: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Bismuth Subsalicylate; Metronidazole; Tetracycline: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Budesonide: (Moderate) Theoretically, induction of the cytochrome P450 3A4 isoenzyme by griseofulvin may result in a lowering of budesonide plasma concentrations, reducing the clinical effect.
Budesonide; Formoterol: (Moderate) Theoretically, induction of the cytochrome P450 3A4 isoenzyme by griseofulvin may result in a lowering of budesonide plasma concentrations, reducing the clinical effect.
Budesonide; Glycopyrrolate; Formoterol: (Moderate) Theoretically, induction of the cytochrome P450 3A4 isoenzyme by griseofulvin may result in a lowering of budesonide plasma concentrations, reducing the clinical effect.
Butalbital; Aspirin; Caffeine; Codeine: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Choline Salicylate; Magnesium Salicylate: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Cyclosporine: (Moderate) Griseofulvin has been reported to reduce cyclosporine serum concentrations. Although very few reports of this interaction are known, the sequelae from this combination are significant. Closely monitor cyclosporine levels during concurrent treatment with griseofulvin. An increase in cyclosporine dose may be necessary if griseofulvin is added. The cyclosporine dosage may need to decreased if griseofulvin is discontinued.
Dichlorphenamide: (Moderate) Use dichlorphenamide and griseofulvin together with caution. Dichlorphenamide increases potassium excretion and can cause hypokalemia and should be used cautiously with other drugs that may cause hypokalemia including antifungals. Measure potassium concentrations at baseline and periodically during dichlorphenamide treatment. If hypokalemia occurs or persists, consider reducing the dichlorphenamide dose or discontinuing dichlorphenamide therapy.
Dronabinol: (Major) Oral solutions of dronabinol contain ethanol. Administration of dronabinol oral solution to patients receiving or who have recently received griseofulvin may result in disulfiram-like reactions (e.g., abdominal cramps, nausea/vomiting, headaches, and flushing). A disulfiram reaction would not be expected to occur with non-ethanol containing formulations of dronabinol (e.g., capsules).
Estrogens affected by CYP3A inducers: (Major) Women taking both estrogens and griseofulvin should report breakthrough bleeding to their prescribers. If used for contraception, an alternate or additional form of contraception should be considered in patients prescribed griseofulvin. Higher-dose hormonal regimens may be indicated where acceptable or applicable. The alternative or additional contraceptive agent may need to be continued for 1 month after discontinuation of griseofulvin. Patients taking these hormones for other indications may need to be monitored for reduced clinical effect while on griseofulvin, with dose adjustments made based on clinical efficacy. Concurrent administration may increase estrogen elimination; the mechanism by which griseofulvin enhances estrogen elimination has not been fully elucidated.
Ethanol: (Major) Advise patients to avoid alcohol consumption while taking griseofulvin. Nausea, vomiting, flushing, tachycardia, and severe hypotension have been reported following alcohol ingestion during griseofulvin therapy. (Moderate) Although the injection of alcohol used for therapeutic procedures is not expected to produce significant systemic effects of ethanol, use caution with concomitant use of griseofulvin. Disulfiram-like side effects, including nausea, vomiting, tachycardia, headache, flushing, and abdominal cramps, may occur.
Food: (Moderate) Food can affect the oral bioavailability of griseofulvin. Microsize griseofulvin absorption may be enhanced by concomitant intake of a high-fat meal, but results have been variable.
Halobetasol; Tazarotene: (Moderate) The manufacturer states that tazarotene should be administered with caution in patients who are also taking drugs known to be photosensitizers, such as griseofulvin, as concomitant use may augment phototoxicity. Patients should take care and use proper techniques to limit sunlight and UV exposure of treated areas.
Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate; Sodium Biphosphate: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Lopinavir; Ritonavir: (Major) Oral solutions of lopinavir; ritonavir contain ethanol. Administration of lopinavir; ritonavir oral solution to patients receiving or who have recently received griseofulvin may result in disulfiram-like reactions (e.g., abdominal cramps, nausea/vomiting, headaches, and flushing). A disulfiram reaction would not be expected to occur with non-ethanol containing formulations of lopinavir; ritonavir (e.g., tablets). (Major) Ritonavir oral solution and capsules contain ethanol. Administration of ritonavir oral solution and capsules to patients receiving or who have recently received griseofulvin may result in disulfiram-like reactions (e.g., abdominal cramps, nausea/vomiting, headaches, and flushing). A disulfiram reaction would not be expected to occur with non-ethanol containing formulations of ritonavir (e.g., tablets or oral powder).
Magnesium Salicylate: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Methenamine; Sodium Salicylate: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Methoxsalen: (Moderate) Use methoxsalen and griseofulvin together with caution; the risk of severe burns/photosensitivity may be additive. If concurrent use is necessary, closely monitor patients for signs or symptoms of skin toxicity.
Nirmatrelvir; Ritonavir: (Major) Ritonavir oral solution and capsules contain ethanol. Administration of ritonavir oral solution and capsules to patients receiving or who have recently received griseofulvin may result in disulfiram-like reactions (e.g., abdominal cramps, nausea/vomiting, headaches, and flushing). A disulfiram reaction would not be expected to occur with non-ethanol containing formulations of ritonavir (e.g., tablets or oral powder).
Perampanel: (Major) Start perampanel at a higher initial dose of 4 mg once daily at bedtime when using concurrently with griseofulvin due to a potential reduction in perampanel plasma concentration. If introduction or withdrawal of griseofulvin occurs during perampanel therapy, closely monitor patient response; a dosage adjustment may be necessary. Griseofulvin is a CYP3A4 inducer, and perampanel is a CYP3A4 substrate.
Photosensitizing agents (topical): (Moderate) Griseofulvin may induce photosensitivity and may increase the effects of photosensitizing agents.
Porfimer: (Major) Avoid coadministration of porfimer with griseofulvin due to the risk of increased photosensitivity. Porfimer is a light-activated drug used in photodynamic therapy; all patients treated with porfimer will be photosensitive. Concomitant use of other photosensitizing agents like griseofulvin may increase the risk of a photosensitivity reaction.
Progestins: (Major) The concurrent use of griseofulvin and oral contraceptives can reduce contraceptive efficacy and result in an unintended pregnancy and/or breakthrough bleeding. This risk is particularly serious because griseofulvin is contraindicated during pregnancy due to the risk of teratogenic and abortifacient effects. An alternate or additional form of contraception should be used during concomitant treatment and continued for 1 month after griseofulvin discontinuation. If these drugs are used together, counsel the patient about the risk of pregnancy and teratogenic effects, and instruct the patient to notify the prescriber if they experience breakthrough bleeding while receiving these drugs together. Additionally, patients taking non-oral combination contraceptives or progestins for hormone replacement therapy may also experience reduced clinical efficacy.
Ritonavir: (Major) Ritonavir oral solution and capsules contain ethanol. Administration of ritonavir oral solution and capsules to patients receiving or who have recently received griseofulvin may result in disulfiram-like reactions (e.g., abdominal cramps, nausea/vomiting, headaches, and flushing). A disulfiram reaction would not be expected to occur with non-ethanol containing formulations of ritonavir (e.g., tablets or oral powder).
Rivaroxaban: (Minor) Coadministration of rivaroxaban and griseofulvin may result in decreased rivaroxaban exposure and may decrease the efficacy of rivaroxaban. Griseofulvin is an inducer of CYP3A4, and rivaroxaban is a substrate of CYP3A4. If these drugs are administered concurrently, monitor the patient for signs of lack of efficacy of rivaroxaban.
Saccharomyces boulardii: (Major) Because Saccharomyces boulardii is an active yeast, it would be expected to be inactivated by any antifungals. The manufacturer does not recommend taking in conjunction with any antifungal agents. Patients should avoid use of this probiotic yeast until the fungal or yeast infection is completely treated.
Salicylates: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Salsalate: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
Sulfonylureas: (Moderate) Additive photosensitization may be seen with concurrent administration of sulfonylureas and other photosensitizing agents including griseofulvin. Prevention of photosensitivity includes adequate protection from sources of UV radiation (e.g., avoiding sun exposure and tanning booths) and the use of protective clothing and sunscreens on exposed skin.
Tazarotene: (Moderate) The manufacturer states that tazarotene should be administered with caution in patients who are also taking drugs known to be photosensitizers, such as griseofulvin, as concomitant use may augment phototoxicity. Patients should take care and use proper techniques to limit sunlight and UV exposure of treated areas.
Tretinoin, ATRA: (Moderate) Griseofulvin may increase the CYP450 metabolism of tretinoin, ATRA, potentially resulting in decreased plasma concentrations of tretinoin, ATRA. No specific studies have been done with oral tretinoin and griseofulvin, however, patients should be closely monitored for decreased clinical effects of tretinoin, ATRA while receiving concomitant therapy. Additionally, a manufacturer of topical tretinoin states that tretinoin, ATRA should be administered with caution in patients who are also taking drugs known to be photosensitizers, such as griseofulvin, as concomitant use may augment phototoxicity. Patients should take care and use proper techniques to limit sunlight and UV exposure of treated areas.
Ulipristal: (Major) Avoid administration of ulipristal with drugs that induce CYP3A4. Ulipristal is a substrate of CYP3A4 and griseofulvin is a CYP3A4 inducer. Concomitant use may decrease the plasma concentration and effectiveness of ulipristal.
Verteporfin: (Moderate) Use caution if coadministration of verteporfin with griseofulvin is necessary due to the risk of increased photosensitivity. Verteporfin is a light-activated drug used in photodynamic therapy; all patients treated with verteporfin will be photosensitive. Concomitant use of other photosensitizing agents like griseofulvin may increase the risk of a photosensitivity reaction.
Warfarin: (Major) The anticoagulant effect of warfarin can be decreased if griseofulvin is used concurrently. The griseofulvin-warfarin drug interaction is one of the most well-documented warfarin drug interactions. The mechanism of this interaction is unclear. It is commonly believed that griseofulvin enhances the hepatic metabolism of warfarin. The interaction between warfarin and griseofulvin may require up to 12 weeks to fully manifest and may be more significant with the ultramicrocrystalline formulation of griseofulvin. The international normalized ratio (INR) should be monitored closely if griseofulvin is either added to or discontinued from warfarin therapy.

Fulvicin P/G/Fulvicin U/F/Grifulvin V/Grisactin/Griseofulvin, Microcrystalline/Griseofulvin, Ultramicrocrystalline/Gris-Peg Oral Tab: 125mg, 250mg, 500mg
Grifulvin V/Griseofulvin, Microcrystalline Oral Susp: 5mL, 125mg

1 g/day PO of microsize griseofulvin; 750 mg/day PO of ultramicrosize griseofulvin.

1 g/day PO of microsize griseofulvin; 750 mg/day PO of ultramicrosize griseofulvin.

10 mg/kg/day (Max: 500 mg/day) PO of microsize griseofulvin is FDA-approved; however, doses up to 25 mg/kg/day PO (Max: 1 g/day) have been used off-label; 7.3 mg/kg/day (Max: 375 mg/day) PO of ultramicrosize griseofulvin is FDA-approved; however, doses up to 15 mg/kg/day PO (Max: 750 mg/day) have been used off-label.

3 to 12 years: 10 mg/kg/day (Max: 500 mg/day) PO of microsize griseofulvin is FDA-approved; however, doses up to 25 mg/kg/day PO (Max: 1 g/day) have been used off-label; 7.3 mg/kg/day (Max: 375 mg/day) PO of ultramicrosize griseofulvin is FDA-approved; however, doses up to 15 mg/kg/day PO (Max: 750 mg/day) have been used off-label.
1 to 2 years: Safety and efficacy have not been established.

Safety and efficacy have not been established.

Safety and efficacy have not been established.

Griseofulvin exerts its fungistatic activity primarily by disrupting the mitotic spindle structure of the fungal cell, which causes an arrest of metaphase of cell division. The result is similar to the effect colchicine has on mitosis, albeit by a different mechanism of action. Griseofulvin also may produce defective DNA that is unable to replicate. Griseofulvin is effective in the treatment of superficial dermatophyte infections because it is deposited in keratin precursor cells, creating an unfavorable environment for fungal infection. Infected skin, cells, and hair are then slowly replaced by tissue that is not infected by the dermatophyte. Griseofulvin also possesses a direct vasodilatory effect.

Griseofulvin is administered orally. Griseofulvin concentrates in the skin, hair, nails, fat, and skeletal muscles. It deposits in keratin precursor cells and is tightly bound to new keratin. Concentrations increase rapidly after the first dose and rapidly decrease to undetectable levels after discontinuation. Griseofulvin undergoes hepatic metabolism, mainly through oxidative demethylation and conjugation with glucuronic acid. The major metabolite, 6-desmethylgriseofulvin, is inactive. The half-life is 9—24 hours. Griseofulvin is excreted through the urine, feces, and perspiration.
 
Affected cytochrome P450 isoenzymes: CYP3A4
In vitro data suggest that griseofulvin may induce the CYP3A4 isoenzyme.

Oral griseofulvin is absorbed mainly from the duodenum. Griseofulvin is marketed in several oral formulations in an attempt to increase bioavailability and decrease GI intolerance. Ultramicrosize griseofulvin has almost complete absorption, while microsize griseofulvin has a variable (25—70%) and unpredictable oral absorption. Peak serum concentrations of 0.4—2 mcg/ml are attained 4—8 hours after administration of 500 mg of microsize griseofulvin or 250 mg of ultramicrosize griseofulvin in fasting patients. Microsize griseofulvin absorption may be enhanced by concomitant intake of a high-fat meal, but results have been variable.

Griseofulvin does not penetrate the skin well enough to be administered topically.

Due to possible teratogenic and abortifacient effects, use of griseofulvin during pregnancy is contraindicated. Since 1977, 2 cases of conjoined twins have been reported following first trimester use of griseofulvin. In both cases, surveillance by the FDA found griseofulvin use to be the only maternal drug exposure. In addition to congenital abnormalities, some women who received the drug during pregnancy have experienced spontaneous abortions. An analysis of data from 4,264 spontaneous abortions between 1980 and 1983 revealed 7 women exposed to griseofulvin within the preceding 3 months (RR = 2.5, 95% CI 1.01, 6.1). Pregnant women and women of childbearing age who may become pregnant should be notified of the potential risk to the fetus. Instruct women to use appropriate contraception both during and for 1 month after completing of griseofulvin therapy. Men are advised to wait 6 month after completing griseofulvin therapy before fathering a child. Of note, concurrent use has resulted in reduced oral contraceptive efficacy.  

Data are limited regarding the use of griseofulvin during breast-feeding and it is not known if it is excreted in human breast milk. Due to the potential for adverse effects in a nursing infant, use in a breast-feeding mother is not recommended. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.