Ketoconazole
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Ketoconazole
Nizoral (oral discontinued in US for most fungal indications; topical still widely available)
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Summary
Common uses
Seborrheic dermatitis (topical)0, Tinea versicolor (topical)0, Medical management of Cushing's syndrome (off-label oral, specialty use)0, Off-label oral in advanced prostate cancer (rare)0
Pharmacy
Starting dose
Topical 2% shampoo twice weekly for seborrheic dermatitis or tinea versicolor; oral use restricted by 2013 FDA action to indications where alternatives have failed
Preparations
1% (OTC), 2% (Rx) shampoo; 2% cream; 2% gel; 200 mg oral tablet (rarely used now)
US FDA Max
Topical: regimen-specific; oral: 400 mg/d in remaining specialty indications
Pharmacology
Routes
Topical (cream, shampoo, gel); oral (restricted)
Onset
Topical hours; oral days
Duration
Hours per application (topical); 24 hours (oral)
Half-life
Topical: not meaningfully described; oral 2-8 hours[1]
Bioavailability
Topical: minimal systemic; oral: pH-dependent, requires gastric acid[1]
Pregnancy
Topical generally safe; oral avoided.[citation needed]
Legal status
OTC (1% shampoo) and Rx-only (higher strengths, oral) in US. Oral form carries a Boxed Warning for hepatotoxicity and is restricted by FDA to refractory fungal infections where no alternatives are available
Purported mechanism
Ketoconazole inhibits fungal cytochrome P450 14α-demethylase (CYP51), blocking conversion of lanosterol to ergosterol and disrupting fungal cell membrane integrity.0 Off-target inhibition of mammalian CYP enzymes (especially CYP17, CYP11) at therapeutic systemic concentrations underlies the anti-androgen and anti-cortisol effects exploited in prostate cancer and Cushing's, but also drives oral ketoconazole's adverse profile (gynecomastia, adrenal insufficiency, hepatotoxicity, QT prolongation). Topical use largely avoids these systemic toxicities[1].
References
edit- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Nizoral (ketoconazole), Janssen, current revision (with 2013 black box and indication restriction). https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/018533s039lbl.pdf