Drug reference

Griseofulvin

Antifungal agent (microtubule inhibitor) · Antifungal

Also known as Griseofulvin microsize, Griseofulvin ultramicrosize

START

Confirm dermatophyte infection (KOH prep or culture). Verify not pregnant. Baseline LFTs for long courses. Counsel on need for prolonged therapy and taking with fatty meals.

TYPICAL MAX

1g/day microsize. Duration is the key variable—must continue until infected tissue is replaced. Nail infections require months of therapy.

STOP IF

Severe rash, jaundice, signs of porphyria (abdominal pain, neuropsychiatric symptoms), severe photosensitivity, lupus-like symptoms.

WATCH

LFTs for courses >8 weeks. Photosensitivity—sun protection essential. Efficacy depends on drug depositing in new keratin—takes weeks to see clinical improvement. Terbinafine and itraconazole are generally preferred for onychomycosis (better efficacy, shorter courses).

CDSCO approvedHATC D01AA08

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 1h · Onset ~1 hour
PEAK: 4h · Tmax 2-6 hours (microsize)
t½: 16h · t½ ~9-24 hours
DURATION: 1d · 24 hours (QD)

EXCRETION

Renal as metabolites (~50%)

route + CYP

INTERACTIONS

12 major

SEVERE in our sources

PREGNANCY

Contraindicated in pregnancy—teratogenic in animals (conjoined twins reported). Effective contraception required during and for 1 month after treatment (both sexes).

FDA category + note

Top interactionssee all 12 →

PhenobarbitoneSevereTextbookKDT 7e · p791
Aminolevulinic AcidSevereDatabaseDDInter
DienogestSevereDatabaseDDInter
DrospirenoneSevereDatabaseDDInter

Available in India

76 branded formulations. Look up specific brands in the Drugs workspace.

Mechanism

Depolymerizes fungal microtubules by interacting with tubulin, inhibiting fungal mitosis and cell division. Fungistatic. Selectively concentrates in keratin precursor cells, making newly formed hair, skin, and nails resistant to fungal invasion.

Indications

Dermatophyte infections of scalp (tinea capitis)Dermatophyte infections of body (tinea corporis)Dermatophyte infections of nails (tinea unguium / onychomycosis—less effective than newer agents)Tinea pedis / tinea cruris (when topical therapy fails)

Dosing

Adult: Microsize: 500mg PO daily (single or divided). Ultramicrosize: 330-375mg PO daily. Tinea capitis: 500mg-1g/day x 4-8 weeks. Onychomycosis: 500mg-1g/day x 6-12 months (fingernails) or 12-18 months (toenails). Take with fatty meal.
Pediatric: Microsize: 10-20mg/kg/day (max 1g). Ultramicrosize: 5-10mg/kg/day. Tinea capitis: 6-8 weeks.
Renal adjustment: No adjustment needed.
Hepatic adjustment: Use caution; avoid in severe hepatic impairment.
Geriatric: No specific adjustment.
Max dose: 1g/day (microsize); 750mg/day (ultramicrosize)

Pharmacokinetics

Onset

Weeks to months (must wait for new keratin to replace infected tissue)

Peak effect

Tmax 2-6 hours (microsize); 1-2 hours (ultramicrosize); accumulates in keratin over weeks

Duration

24 hours (QD dosing)

Half-life

~9-24 hours (dose-dependent; ultramicrosize has better absorption)

Bioavailability

~25-70% (highly variable; ultramicrosize 1.5x better absorbed than microsize; enhanced by fatty meals)

Protein binding

~82%

Metabolism

Extensive hepatic via demethylation and glucuronidation

Excretion

~50% renal (metabolites); ~35% fecal

Contraindications

Hypersensitivity to griseofulvin
Porphyria (can trigger acute attacks)
Severe hepatic disease
Systemic lupus erythematosus (may exacerbate)
Pregnancy (contraindicated—teratogenic)

Side effects

Common

HeadacheNausea and vomitingDiarrheaFatigueDizzinessInsomniaPhotosensitivityRash

Serious

Severe hepatotoxicity
Severe cutaneous reactions (SJS/TEN)
Acute porphyria attacks
Blood dyscrasias (leukopenia, neutropenia)
Lupus-like syndrome
Angioedema
Severe photosensitivity reactions

Pregnancy & lactation

Pregnancy

Contraindicated in pregnancy—teratogenic in animals (conjoined twins reported). Effective contraception required during and for 1 month after treatment (both sexes).

Lactation

Excreted in breast milk; avoid during breastfeeding (theoretical risk to infant).

Drug interactions

Phenobarbitone

Severe

Textbook

Failure of griseofulvin therapy may occur.

Source: KDT 7e · p791

Aminolevulinic Acid

Severe

Database

Drug interaction classified as: synergy

Source: DDInter

Dienogest

Severe

Database

Clinical effect not specified

Source: DDInter

Drospirenone

Severe

Database

Clinical effect not specified

Source: DDInter

Ethinylestradiol

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Etonogestrel

Severe

Database

Drug interaction classified as: metabolism

Source: DDInter

Levacetylmethadol

Severe

Database

Clinical effect not specified

Source: DDInter

Levonorgestrel

Severe

Database

Clinical effect not specified

Source: DDInter

Lumateperone

Severe

Database

Clinical effect not specified

Source: DDInter

Medroxyprogesterone Acetate

Severe

Database

Decreased plasma concentrations and efficacy of medroxyprogesterone acetate, leading to potential breakthrough bleeding or reduced contraceptive efficacy.

Consider alternative or additional contraceptive methods during and for at least 4 weeks after stopping griseofulvin. Monitor for reduced efficacy.

Source: DDInter

Norethisterone

Severe

Database

Reduced plasma concentrations of norethisterone, potentially leading to decreased contraceptive efficacy and increased risk of breakthrough bleeding or unintended pregnancy.

Advise patients to use an additional barrier method of contraception during griseofulvin treatment and for at least 4 weeks after discontinuation. Consider alternative antifungals if possible.

Source: DDInter

Norgestimate

Severe

Database

Clinical effect not specified

Source: DDInter