Etretinate has a low therapeutic index and a long elimination half-life (t1/2) of 120 days, which make dosing difficult. Etretinate is an aromatic retinoid, and therefore highly lipophilic. It is stored and released from adipose tissue, so its effects can continue long after dosage stops. It is detectable in the plasma for up to three years following therapy. Etretinate has been replaced by acitretin, a safer metabolite of etretinate. Etretinate is a teratogen, and may cause birth defects long after use. Therefore, birth control is advised during therapy, and for at least three years after therapy has stopped. Etretinate should be avoided in children, as it may interfere with bone growth. If a patient has ever taken etretinate, he or she is not eligible to donate blood, due to the risk of birth defects. Etretinate is an aromatic retinoid given orally to treat severe psoriasis, a chronic disease that often requires long-term therapy.
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