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Minocycline can cause hyperpigmentation of skin, nail beds, thyroid, sclera, bones, and teeth. Oral pigmentation, which has rarely been reported, is considered to be due to visualization through the oral mucosa of dark, insoluble salts of minocycline in bone. In this study, 331 patients who had taken at least 100 mg minocycline daily for a minimum of six months for acne were examined for oral pigmentation.
Thirty-three patients had blue or blue-black oral pigmentation. This was localized to areas with bone beneath the mucosa, but not gingival or buccal mucosa, as has been reported in other studies. Darkening of skin, nails, or teeth was not seen. Only five patients were aware of discoloration. The incidence of pigmentation increased with dos…