Pharmacokinetic data of gamma-linolenic acid in healthy volunteers after the administration of evening primrose oil (Epogam).

Defects in the metabolism of gamma-linolenic acid are thought to play a major role in the pathogenesis of atopic eczema, but little is known about the pharmacokinetic behavior of this fatty acid and its metabolic products. We investigated the serum level-time courses of 8 fatty acids after the administration of Epogam, a preparation of evening primrose oil which contains gamma-linolenic acid as an active ingredient. From 6 volunteers, serum concentration time curves of gamma-linolenic acid and 7 other fatty acids were profiled 24 h with and without the administration of Epogam. Six capsules of Epogam were administered to each subject in the morning at 7:00 and further 6 capsules in the evening at 19:00. On the days of investigation the volunteers had a diet of low fat meals. The serum concentrations of the fatty acids were determined as their methyl esters by means of gas chromatography mass spectrometry. Gamma-linolenic acid shows an absorption-elimination pattern after the administration of Epogam and its AUC24h and Cmax are significantly increased over the baseline values. After the evening administration, t(max) is shorter (2.7 +/- 1.2 h) than after the morning administration (4.4 +/- 1.9 h). The other fatty acids show no significant increase in their concentrations, especially dihomo-gamma-linolenic acid and arachidonic acid, which are metabolic products of gamma-linolenic acid. Conclusively, an effect of the administration of gamma-linolenic acid on the serum concentrations of dihomo-gamma-linolenic acid and arachidonic acid and, therefore, on the biosynthesis of prostaglandin PGE1 and PGE2 could not clearly be established in healthy volunteers. Further investigations will show if there is a significant effect in patients suffering from atopic eczema.