[Trans-acitretin is metabolized back to etretinate. Importance for oral retinoid therapy]

The oral retinoid etretinate (Tigason) has recently been replaced by trans-acitretin (Neotigason) in the treatment of severe psoriasis, primarily because of its short half-life and the assumption that a shorter period of subsequent contraception would be required. After introduction of the new drug, however, circulating quantities of etretinate were detected in patients treated with trans-acitretin. Thus far, re-esterification has been detected in at least 83 cases. The 2-month period of strict contraception initially recommended after oral intake of trans-acitretin has been extended to 2 years, as with etretinate. We review some aspects of trans-acitretin metabolism, with special emphasis on etretinate formation. Re-esterification of trans-acitretin into etretinate takes place under varying conditions in volunteers and patients, as well as in animal models. Ethanol is a co-factor for the enzymatic re-esterification of trans-acitretin. It is unclear whether the introduction of trans-acitretin has been of any significant benefit to patients. Monitoring of plasma retinoid levels during and after retinoid therapy remains of decisive importance in managing difficult cases and or in approving decisions for pregnancy.