Imipramine-Induced Hyperpigmentation

Comment

Drug-induced hyperpigmentation accounts for 10% to 20% of all cases of acquired hyperpigmentation.¹ Common causative drugs include amiodarone, antimalarials, minocycline, and rarely psychotropics including phenothiazines and tricyclic antidepressants such as imipramine.^1-4 Although amiodarone-induced hyperpigmentation is associated with lipofuscin in addition to melanin, most other medications, including imipramine, induce cutaneous effects through deposition of melanin and/or hemosiderin. A review of the histopathologic staining characteristics in pigment anomalies caused by these drugs is summarized in the Table.

Imipramine-induced hyperpigmentation presents as slate gray discrete macules and patches on sun-exposed skin that may appear anywhere from 2 to 22 years after initiating the medication.^1-4 Affected areas include the malar cheeks, temples, periorbital areas, hands, forearms, and seldom the iris and sclera.^2-4 Although the blue to slate gray coloring is classic, other colors have been described including brown, golden brown, and purple.²

Histopathology of imipramine-induced hyperpigmentation shows golden brown, round to oval granules in the superficial dermis and within dermal macrophages.^1,3 Generally, Fontana-Masson staining is positive for melanin and Perls Prussian blue staining is negative for iron.^1,2,4

Imipramine-induced hyperpigmentation likely results from photoexcitation of imipramine or one of its metabolites. These compounds activate tyrosinase, increasing melanogenesis and leading to formation of melanin-imipramine or melanin-metabolite complexes.^1-3 Complexes are deposited in the dermis and basal layer or are engulfed by dermal macrophages and darkened on sun exposure due to their high melanin content.¹ Other possible mechanisms of hyperpigmentation include nonspecific inflammation caused by the drug in the skin, hemosiderin deposition from vessel damage and subsequent erythrocyte extravasation, or deposition of newly formed pigments related to the drug.¹

Most patients report satisfactory resolution of imipramine-induced discoloration within 1 year of stopping imipramine or switching to a different antidepressant.^1,4 Patients who are unwilling to discontinue imipramine may achieve resolution with alexandrite or Q-switched ruby laser therapy.^1,4 Strict sun protective measures are necessary, both to prevent new deposition of melanin and to prevent darkening of existing pigment.

Despite the advent of new psychotropic medications, imipramine remains the antidepressant of choice for many patients. Although rare, it is important to be able to recognize imipramine-induced hyperpigmentation and to encourage patient-psychiatrist communication to determine an antidepressant regimen that avoids unnecessary cutaneous side effects.