Simvastatin and amlodipine induced thrombocytopenia in the same patient: double trouble and a literature review

Abstract

Drug-induced thrombocytopenia (DITP) may be a fatal adverse reaction to many drugs. It is often misdiagnosed as primary immune thrombocytopenia (ITP), and thus diagnosis can be delayed and patients can be treated inappropriately. Amlodipine a calcium-channel blocker, and simvastatin, a statin, have very rarely been implicated in DITP. We report on an investigation of the causal relationship of amlodipine and simvastatin with thrombocytopenia occurring in the same patient, and review the literature. We present the case of a 78-year-old female hypertensive diabetic patient with three successive DITPs. The first attack of acute severe thrombocytopenia occurred after a 2-week course of amlodipine, and was initially misdiagnosed as ITP. Her platelet count normalized after the amlodipine was discontinued. The second attack followed her restarting simvastatin 3 weeks later. She had stopped it 2 months earlier having previously taken it for over 5 years. Again, she recovered once the simvastatin was discontinued. The third DITP attack occurred when she accidently took a single dose of amlodipine 9 months later. We provide clear evidence of a causal association of amlodipine with thrombocytopenia, and probable evidence of a causal association of simvastatin with thrombocytopenia. This is the first reported case of DITPs occurring with two of the most widely prescribed drugs in the same patient. Many hypertensive patients need to take multiple drugs in order to achieve their treatment goals and this increases their risk of drug-induced adverse reactions and makes identification of the causal drug (or drugs) extremely difficult.