Pharmacokinetics
Isotretinoin, when administered orally, is best absorbed when taken after a high-fat meal, as it has a high level of lipophilicity. In a crossover study, the peak plasma concentration was found to be more than doubled when taken after a high-fat meal versus a fasted condition. Isotretinoin is primarily (99.9%) bound to plasma proteins, mostly albumin. At least three metabolites have been detected in human plasma after oral administration: 4-oxo-isotretinoin, retinoic acid, and 4-oxo-retinoic acid. Isotretinoin also oxidizes, irreversibly, to 4-oxo-isotretinoin. The metabolites of isotretinoin are excreted through both urine and feces. The mean elimination half-life is 21 hours, with a standard deviation from this mean of 8.2 hours.
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