Photosensitivity and hyperpigmentation in amiodarone-treated patients: incidence, time course, and recovery.

Amiodarone (AD) induces photosensitivity in 75% of the patients treated with this drug. Phototoxic reactions can be experimentally elicited with UVA but not with UVB. The UVA-MED is significantly reduced after 12 months of treatment. The development of photosensitivity depends on the total dose of AD; 40 g is the minimal cumulative dose requirement. Under the regimens commonly used, photosensitivity can be expected after 4 months of continuous AD treatment and appears to be unrelated to the skin type. Photosensitivity gradually decreases and returns to normal between 4 and 12 months after the withdrawal of AD. AD-related hyperpigmentation develops after an average of 20 months of continuous AD treatment and a minimal total dose of 160 g AD in about 8% of the patients (mainly of skin type I). Electron microscopic examination of the sun-exposed skin of patients without AD discoloration shows pigment deposits similar to those already described in patients with AD hyperpigmentation in exposed and non-exposed skin. Light and electronmicroscopic examination of sun-exposed skin of both clinically photosensitive and non-photosensitive patients reveals perivascular inflammation even in the absence of a clinical rash. Reduplications of vascular basal laminae occur in sun-exposed skin of both patients with and without UVA photosensitivity but are absent from non-exposed skin. In one patient, followed for 33 months after drug withdrawal, massive AD-induced hyperpigmentation was found to be reversible.