What is Griseofulvin Ultramicrocrystalline?
Griseofulvin ultramicrocrystalline is a specific pharmaceutical formulation of the antifungal drug griseofulvin that has been processed into extremely small particles to enhance absorption from the gastrointestinal tract, allowing for lower doses compared to the standard micronized formulation. 1
Pharmaceutical Formulation and Absorption
- Griseofulvin is available in several particle size formulations including micronized, ultramicronized (also called ultramicrocrystalline), and suspension forms 1
- The ultramicrocrystalline formulation improves bioavailability because the smaller particle size increases the surface area available for absorption 2
- Absorption is significantly enhanced when taken with fatty food, which should be recommended to all patients regardless of formulation 1, 3
- Peak plasma concentrations occur approximately 4 hours after oral administration 2
Dosing Differences Between Formulations
- Dosage recommendations vary according to the type of formulation used and how easily it is absorbed 1
- The ultramicrocrystalline form requires lower doses than the micronized form to achieve equivalent therapeutic effects 1
- For tinea capitis in children, the standard licensed dose is 20 mg/kg daily (can be given as single or divided doses) for 6-8 weeks if body weight is less than 50 kg 1
- In resistant cases, doses up to 25 mg/kg daily may be necessary for more prolonged periods 1, 3
Mechanism of Action
- Griseofulvin is a fungistatic drug that inhibits nucleic acid synthesis and arrests cell division at metaphase 1
- It impairs synthesis of the fungal cell wall and interferes with the function of microtubules 1, 2
- The drug is deposited in newly formed keratin cells of skin, hair, and nails, making these tissues resistant to fungal invasion 2
Clinical Context and Current Status
- Griseofulvin remains the only licensed oral antifungal product for use in the treatment of tinea capitis in children in the U.K., with over 50 years of clinical experience 1
- The suspension formulation is no longer licensed in the U.K., and griseofulvin tablets are no longer available in some European countries, having been superseded by other agents 1, 4
- The drug has become increasingly expensive and not widely available in certain formulations 1
Important Clinical Caveat
- While ultramicrocrystalline griseofulvin offers improved absorption, the drug itself has significant limitations: it shows poor efficacy for toenail onychomycosis (only 30-40% mycological cure rates), requires lengthy treatment durations (12-18 months for toenails), and has been superseded by newer agents like terbinafine for most dermatophyte infections except Microsporum tinea capitis 1, 3