| Absorption: |
| Plasma levels peak in ~4 hr after administration PO, but absorption from the GI tract continues over a prolonged period. Absorption is highly variable, being influenced by a number of factors. The rates of disaggregation and dissolution in the GI tract limit the bioavailability of griseofulvin; thus, microsized and ultramicrosized particles are usually used. High-fat meals, margarine, or propylene glycol significantly enhance GI absorption of griseofulvin and are indicated if
the microsized particles are used. |
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| Distribution: |
| Griseofulvin is deposited in keratin precursor cells within 4-8 hr of administration PO. Sweat and transdermal fluid loss appear to play an important role in griseofulvin transfer in the stratum corneum. When these cells differentiate, griseofulvin remains bound and persists in keratin, making it resistant to fungal invasion. For this reason, new growth of hair, nails, or horn is the first to become free of fungal infection. As the fungus-containing keratin is shed, it is
replaced by normal skin and hair. Only a small fraction of a dose of griseofulvin remains in the body fluids or tissues. |
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| Biotransformation and Pharmacokinetics: |
| Depending on the species, 10-50% of a griseofulvin dose is excreted almost exclusively as metabolites in the urine, and the remainder in the feces for ~4-5 days after administration. The elimination half-life of griseofulvin is ~24 hr in several species. The drug can be detected in 48-72 hr at the base level of the skin, in 6-12 days in the lower quarter, and in 2-19 days in the middle section of the horny layer. |
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