Nifedipine-induced agranulocytosis: A rare case report and literature review

Drug-induced agranulocytosis (DIAG) is a fatal idiosyncratic reaction characterized by a peripheral neutrophil count <0.5 × 109/L. Almost all classes of medications have been implicated with DIAG. However, agranulocytosis induced by antihypertensive drugs is rare worldwide. To the best of our knowledge, this is the first case of nifedipine-associated agranulocytosis with a positive rechallenge. An 82-year-old man was admitted to our hospital due to uncontrolled fasting blood sugar. He had a history of hypertension and underwent treatment with nifedipine 6 years prior to admission. Blood tests showed white blood cell count of 2.30 × 109/L with a neutrophil count of 0.49 × 109/L. Other malignancies that contributed to agranulocytosis were excluded, and the patient was diagnosed with DIAG. At first, gliclazide, rather than nifedipine, was considered as the culprit for DIAG and it was discontinued. Neutrophil count improved upon hematopoietic growth factors and traditional Chinese medicine. During the follow-up, the neutrophil count decreased again, and nifedipine was thought to be the offending agent for agranulocytosis. The neutrophil count increased to 0.91 × 109/L 2 months after nifedipine discontinuation. However, the patient was re-exposed to nifedipine and the neutrophil count decreased to 0.70 × 109/L. Nifedipine-induced agranulocytosis is a rare but serious adverse drug reaction. For any patients with clinical suspicion or diagnosis of DIAG, a full drug history should be chronologically and completely taken in order to identify the suspected agents. Sometimes diagnosis of DIAG is challenging since some patients may be entirely asymptomatic. Management of DIAG starts with immediate discontinuation of the implicated drug. Empirical broad-spectrum antibiotics and hematopoietic growth factors may improve patient outcomes and reduce recovery time.