Griseofulvin (griseofulvin, microsize)

Dosage of griseofulvin varies depending on whether the drug is administered as griseofulvin microsize or griseofulvin ultramicrosize. In addition, dosage recommendations for ultramicrosize griseofulvin vary slightly depending on the manufacturer and the particular formulation of the drug.

Dosage and duration of griseofulvin therapy should be individualized according to the requirements and response of the patient. Griseofulvin therapy generally needs to be continued for at least 4-12 weeks for the treatment of tinea capitis; at least 2-4 weeks for the treatment of tinea corporis; at least 4-8 weeks for tinea pedis; and from 4-6 months to a year or longer for tinea unguium.

Griseofulvin is administered orally as a single daily dose or in 2-4 equally divided doses.

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Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Selected Photosensitizers/Tretinoin-Mequinol

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Tretinoin, anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides are all known photosensitizers.(1)

CLINICAL EFFECTS: Concurrent use of tretinoin in patients taking anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides may increase the risk of phototoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer states that tretinoin-mequinol should not be administered to patients receiving photosensitizers including anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides.(1)

DISCUSSION: Because of the risk of increased photosensitivity, the US manufacturer states that tretinoin-mequinol should not be administered to patients receiving photosensitizers including anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), methotrexate, phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides.(1)

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Griseofulvin/Contraceptives

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Unknown. However, possibly due to increased metabolism of oral contraceptives.

CLINICAL EFFECTS: Decreased effectiveness of oral contraceptives, producing breakthrough bleeding, amenorrhea and unintended pregnancy.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The patient should use an alternative method of contraception during and for one month after receiving griseofulvin. Increasing the dose of estrogen may be necessary in patients on low-dose estrogen. For emergency contraception, the UK's Medicines & Healthcare Products Regulatory Agency (MHRA) recommends that women who have used an inducer in the previous 4 weeks should consider a non-hormonal emergency contraceptive (ie a copper IUD). If a non-hormonal emergency contraceptive is not an option, double the usual dose of levonorgestrel from 1.5 to 3 mg. Advise the patient to have a pregnancy test to exclude pregnancy after use and to seek medical advice if they do become pregnant.

DISCUSSION: Loss of oral contraceptive efficacy has been reported following the addition of griseofulvin to the patient's drug therapy. Loss of efficacy was indicated by breakthrough bleeding, amenorrhea and unintended pregnancy.

Selected Photosensitizers/Aminolevulinic Acid

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Aminolevulinic acid, anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides are all known photosensitizers.(1)

CLINICAL EFFECTS: Concurrent use of aminolevulinic acid in patients taking anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides may increase the risk of phototoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer states that aminolevulinic acid should be avoided in patients receiving photosensitizers including anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides for 24 hours before and after administration of aminolevulinic acid.(1)

DISCUSSION: Because of the risk of increased photosensitivity, the US manufacturer states that aminolevulinic acid should be avoided in patients receiving photosensitizers including anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides for 24 hours before and after administration of aminolevulinic acid.(1)

Selected Photosensitizers/Methoxsalen

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Methoxsalen causes photosensitivity due to residual drug which is present in all parts of the skin from photopheresis. Anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides are other known photosensitizers.(1)

CLINICAL EFFECTS: Concurrent use of methoxsalen in patients taking anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides may increase the risk of phototoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of methoxsalen states that concurrent use of methoxsalen with anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides should be avoided.(1)

DISCUSSION: All patients who have received methoxsalen become photosensitive. It is unknown what the risk of photosensitivity reactions is when methoxsalen is used concurrently with other photosensitizing agents.(1)

Selected Photosensitizers/Porfimer

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Porfimer causes photosensitivity due to residual drug which is present in all parts of the skin. Anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides are other known photosensitizers.(1)

CLINICAL EFFECTS: Concurrent use of porfimer in patients taking anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides may increase the risk of phototoxicity.(1)

PREDISPOSING FACTORS: Patients with any hepatic impairment and patients with severe renal impairment have reduced drug elimination and may remain photosensitive for 90 days or longer.(1)

PATIENT MANAGEMENT: The US manufacturer of porfimer states that concurrent use of porfimer with photosensitizers including anthralin, coal tar and derivatives, fluoroquinolones, griseofulvin, organic staining dyes (such as methylene blue, rose bengal, or toluidine blue), phenothiazines, selected NSAIDs (such as diclofenac, ketoprofen, nabumetone, naproxen, piroxicam, and tiaprofenic acid), methotrexate, St. John's wort, sulfonamides, sulfonylureas, tetracyclines, and thiazides should be avoided.(1) Since the photosensitive effect of porfimer may persist for at least 30 days (and for 90 days in some patients), it would be prudent to avoid other photosensitizing agents for at least 30 days after administration of porfimer.

DISCUSSION: All patients who have received porfimer become photosensitive. It is unknown what the risk of photosensitivity reactions is when porfimer is used concurrently with other photosensitizing agents. When porfimer was used in clinical trials, photosensitivity reactions occurred in about 20% of cancer patients and in 69% of high-grade dysplasia in Barretts esophagus patients. Most of the reactions were mild to moderate erythema, but they also included swelling, pruritus, burning sensation, feeling hot, or blisters. The majority of reactions occurred within 90 days of porfimer administration.(1)

Moderate Interaction: Assess the risk to the patient and take action as needed.

Griseofulvin/Selected Anticoagulants (Vitamin K Antagonists)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Griseofulvin may induce the metabolism of Vitamin K antagonists, such as warfarin.

CLINICAL EFFECTS: Concurrent or recent use of griseofulvin may result in decreased anticoagulant response, which can increase the risk of thrombosis.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Use caution when griseofulvin is started or stopped in patients on anticoagulant therapy. Monitor INR closely and adjust the anticoagulant dose as necessary. The time of highest risk for a coumarin-type drug interaction is when the precipitant drug is initiated or discontinued. Contact the prescriber before initiating, altering the dose or discontinuing either drug.

DISCUSSION: Several case reports have shown that the administration of griseofulvin (500mg/day to 1000mg/day) to patients maintained on warfarin resulted in a decreased prothrombin time, requiring an increase in the dose of warfarin.(1,2) This interaction usually occurs after several weeks of concurrent therapy. In one patient, an overall increase of 41% in warfarin dosage (from 8.5mg/day to 12mg/day) was needed to maintain the therapeutic effect of warfarin after 12 weeks of co-administration. Nine weeks after the griseofulvin dosage was reduced (from 500mg/day to 250mg/day), the prothrombin time increased to 2.3 times control. A reduction in the dose of warfarin to 10mg/day maintained the prothrombin time between 1.6 and 1.8 times control for the next seven weeks.(1) In a small study in which patients served as their own controls, 4 of 10 subjects experienced a decrease in prothrombin times following two weeks of griseofulvin therapy.(3)

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• Hepatic failure
• Porphyria
• Pregnancy

• Disease of liver

• Alcohol use disorder
• Granulocytopenic disorder
• Lupus-like syndrome
• Systemic lupus erythematosus

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Less Frequent

• Acute cognitive impairment
• Granulocytopenic disorder
• Hepatitis
• Leukopenia
• Oral candidiasis
• Peripheral neuropathy
• Skin photosensitivity
• Skin rash
• Urticaria

Rare or Very Rare

• Abnormal hepatic function tests
• Angioedema
• Erythema multiforme
• Hyperbilirubinemia
• Lupus-like syndrome
• Stevens-johnson syndrome
• Toxic epidermal necrolysis

More Frequent

• Headache disorder

Less Frequent

• Diarrhea
• Dizziness
• Fatigue
• Gastrointestinal irritation
• Insomnia
• Nausea
• Proteinuria
• Vomiting

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Griseofulvin may cause fetal toxicity when administered to pregnant women. Griseofulvin is embryotoxic and/or teratogenic in animals. Fetal abnormalities have included multiple defects in rats; cleft palate in dogs; cleft palate and cardiac, CNS, and ocular defects in cats; and skeletal defects in mice. Although the potential risk to the fetus of maternal use of griseofulvin remains to be clearly established in humans, at least two women who received griseofulvin therapy during the first trimester of pregnancy delivered conjoined twins, and some women who received the drug during pregnancy reportedly have had spontaneous abortions or delivered infants with other congenital malformations. In an analysis of spontaneous or threatened abortion diagnoses in one large group of women, the estimated relative risk of spontaneous abortion in women who received griseofulvin within the 3 months prior to such diagnoses was estimated to be increased 2.5 times. Some experts state that while limited data indicate that the outcome for most pregnancies is likely to be normal after fetal exposure to the drug, evidence from the US Food and Drug Administration's teratogen information system indicates that an association between conjoined twins and griseofulvin use exists and data are insufficient to exclude a moderate association between use of the drug and other defects. However, other experts have questioned whether an association between use of the drug and conjoined twinning has been established. The manufacturers state that griseofulvin is contraindicated in women who are or may become pregnant. One manufacturer states that additional contraceptive precautions should be taken during and for 1 month after griseofulvin therapy and that griseofulvin should not be used in any woman who intends to become pregnant within 1 month after therapy with the drug would be discontinued. If griseofulvin is inadvertently administered during pregnancy or if the patient becomes pregnant while receiving the drug, the patient should be informed of the potential hazard to the fetus.

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