Effect of Phenothiazine on the Red Cells of Paroxysmal Nocturnal Haemoglobinuria

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Abstract
Summary. A phenothiazine derivative (chlorpromazine hydrochloride) was investigated as a possible means of reducing the transfusion requirement of patients with paroxysmal nocturnal haemoglobinuria. Results of in‐vitro studies have indicated that the drug has both beneficial and detrimental effects on the PNH red cell. Thus, while the osmotic haemolysis time is increased and the degree of acid haemolysis (Ham's test) is decreased, the osmotic fragility is increased on incubation. An in‐vivo survival study of ficin‐treated rabbit red cells showed no beneficial effect when the rabbits were primed with phenothiazine. It is therefore suggested that whenever drugs of the phenothiazine family are used, it should be with an awareness of potential haemolytic side effects in PNH and possibly in other haemolytic disorders.