Etretinate. A review of its pharmacological properties and therapeutic efficacy in psoriasis and other skin disorders.

Etretinate (Ro 10-9359) is a new aromatic retinoic acid derivative for the treatment of severe psoriasis and other dyskeratoses. The pharmacological profile of etretinate suggests that it acts by normalizing pathological changes in epidermal and dermal skin, particularly inhibiting hyperkeratinization and cell differentiation, although its specific mode of action in different disorders remains to be elucidated. Etretinate is rapidly and presystemically metabolised to an active metabolite which appears in plasma at about the same time as parent drug. A 'deep' storage compartment with a very extended elimination half-life gives rise to detectable plasma levels of drug for at least 3 to 4 months after discontinuation of long term therapy. Studies suggest that etretinate at an initial dose of 1 mg/kg/day, reducible during maintenance therapy, is an effective alternative to PUVA and other conventional therapy in severe psoriasis. Its greatest immediate value is in the control of eruptive and treatment-resistant psoriasis, and in its potential for use in combination with other therapy to improve the response. In Darier's disease it appears to be the treatment of choice, and preliminary studies also suggest its usefulness in ichthyosis, and most other dyskeratoses and possibly in basal cell carcinoma. Side effects affecting the mucocutaneous system occur in nearly all patients, but rarely lead to drug withdrawal. When withdrawal does become necessary, the primary reason is usually hair loss. A few paradoxical observations of raised and lowered liver enzyme levels have been reported, and also a few cases of suspected liver damage. Etretinate is strictly contraindicated in women of child-bearing potential due to its severe teratogenic properties.