Association between drug use and acute immune thrombocytopenia in adults: a case-control study from the Berlin Pharmacovigilance Center PVZ-FAKOS

Background and Aim: Drug induced acute immune thrombocytopenia (ITP) can be triggered by numerous medications. Aim of our study was to quantify the risk of acute ITP for a wide range of drugs. Materials and Methods: Case-control study including 135 cases of acute ITP leading to hospitalization and 731 control patients aged 18 years and older. Cases were defined as patients with idiopathic or symptomatic ITP and patients with suspected drug induced ITP who had a platelet count ≤100.000/µl. Patients with heparin-induced immune thrombocytopenia were not included as cases. Cases and controls were recruited in 51 hospitals in Berlin within the framework of the active surveillance conducted by the Berlin Pharmacovigilance Centre. Detailed drug information was obtained in a standardized personal interview. Odds ratios of ITP associated with drug exposure within one week before the index date (onset of ITP, day of hospital admission for controls) were calculated by logistic regression analysis adjusting for sex and age. Results: Use of triamteren combined with hydrochlorothiazide (adjusted OR 4.9; 95% CI, 1.2–19), drospirenone combined with ethinylestradiol (OR 7.4; CI 1.2–58.4), cotrimoxazole (OR 7.1; CI 1.5–37), and amitriptyline (OR 12.8; CI 1.2–279.3) were significantly associated with an increased risk of developing acute ITP. Increased risk estimates, although not significant, were observed for phenprocoumon (OR 2.0; CI 0.9–4.2), amlodipine (OR 2.1; CI 0.9–4.6), and chlormadinone combined with ethinylestradiol (OR 8.9; CI 0.8–194.4). No increased risks were observed for non-steroidal anti-inflammatory drugs (NSAIDs), ACE inhibitors or antidiabetic drugs. Conclusion: Our study showed increased risks for several medications. Drug induced acute ITP should be considered in a patient presenting with unexpected sudden thrombocytopenia who is receiving these medications. Acknowledgement: PVZ-FAKOS is being funded by the Federal Institute for Drugs and Medical Devices, Germany