Medication-induced oral hyperpigmentation is an adverse drug reaction that may develop rapidly after taking a drug once or for several continuous days or years.<br />On oral examination, MIOH appear as localized or generalized areas of blue to ill-defined black pigmentation in any site in the oral cavity. Gingiva, tongue and buccal mucosa are the most commonly affected. Diagnosis depends on detailed medical history and clinical manifestations. The exact mechanism of MIOH is unknown but it is proposed that it may be due to increased number of melanocytes in tissues, melanin production, and/or deposition/accumulation of drug metabolites.<br />The practitioners and dentists should be aware of medications associated with oral hyperpigmentation to accomplish full patient reassurance and monitoring the potential side effects.<br />Common medications that cause MIOH include: minocycline, antimalarials, clofazimine, oral contraceptives, amiodarone, zidovudine, chlorpromazine, ketoconazole, busulfan, doxorubicin, bleomycin, cyclophosphamide, 5- fluorouracil, nicotine, heroin, nitrogen mustard, phenothiazines, arsenic, silver, lead, mercury, progesterone, and imatinib mesylate.<br /> Sometimes one or more well- demarcated, round or oval, slate- brown colored macules appear after cotrimoxazole and tetracycline therapy. Nonsteroidal anti-inflammatory drugs or a number of antihypertensive medications can cause post- inflammatory hyperpigmentation when lichenoid drug eruption resolves.<br /><br />Assistant lecturer <br />Hanadi H. Al-Khafaji<br />