亞甲藍是一種解毒藥，為深綠色、有銅光的柱狀結晶或結晶性粉末；無臭。高濃度時直接使血紅蛋白氧化為高鐵血紅蛋白。低濃度時，在還原型輔酶I脫氫酶（NADPH）作用下，還原成為還原型亞甲藍，能將高鐵還原型蛋白還原為血紅蛋白。在體內借酶的參與，起着遞氫體作用。不同劑量對血紅蛋白效應不同，大劑量（或高濃度）治療氰化物中毒。本藥靜脈注射作用迅速，並還原為無色亞甲藍，在6d內74%由尿排出，部分從膽汁排出。腎功能不良者，血濃度可升高。本藥主要損害胃腸道、心血管和中樞神經系統、腎臟等。亞甲藍不能做皮下、肌內和椎管內注射。椎管內注射易引起中樞神經系統永久性器質性損害，皮下注射易產生局部壞死性膿腫。

The patient had received 200 mg methylene blue (MB), i.v., for treatment of septic shock 90 min prior to death. Analysis of tissue samples by liquid extraction and liquid chromatography coupled to tandem mass spectrometry demonstrated different concentrations of MB and its metabolites azure A and B in the heart, lungs, kidneys, and liver. Our findings clearly demonstrate the relation of MB administration and organ discolouration at autopsy and shed a new light on MB distribution and accumulation in septic shock.