Drug-induced thrombocytopenia is a rare immune-mediated reaction in which platelet destruction is induced by several mechanisms, most important being bone marrow suppression and/ or antibody formation. The clinical presentation depends on the severity of thrombocytopenia, ranging from mild ecchymoses and petechiae to life-threatening central nervous system or gastrointestinal bleeding. After confirming low platelet count in blood work, a thorough patient history is essential to identify the drug responsible for thrombocytopenia.
Drug-induced thrombocytopenia is an uncommon phenomenon characterized by a reduced platelet count (< 50×10^9/L) after the use of various drugs    . Quinine, quinidine, antibiotics (trimethoprim-sulfamethoxazole, vancomycin, linezolid, rifampin, ceftriaxone and penicillins), antiepileptic drugs (carbamazepine), glycoprotein IIb/IIIa inhibitors (abciximab and eptifibatide), cytotoxic agents, and heparin are described as some of the most common drugs known to cause thrombocytopenia in the literature   . Signs and symptoms, in the form of bleeding disorders, usually start at least one week after drug use   . Some drugs, however, such as abciximab, can induce the formation of drug-dependent antibodies within hours . In patients with milder thrombocytopenia, principal signs include petechiae, epistaxis, ecchymoses, bruising, and mucosal bleeding, seen in up to two-thirds of patients  . On the other hand, severe gastrointestinal bleeding, hematuria, purpura of the skin and mucosal surfaces, but also intracranial hemorrhage that may be life-threatening, are reported in the case of severe thrombocytopenia (< 10x109/L)  . With the cessation of the offending drug, signs, and symptoms might completely disappear within a few days, but in the absence of an early diagnosis, fatal hemorrhage can occur  .
The sudden onset of symptoms related to bleeding disorders must raise suspicion toward an iatrogenic cause . Many authors have stressed the pivotal role of a properly obtained patient history to confirm whether prescribed drugs are responsible for the presenting signs and symptoms   . Physicians must perform a meticulous examination of the skin and mucosal tissues, and laboratory studies to confirm thrombocytopenia   . The severity of bleeding manifestations often (but not always) correlate with the degree of thrombocytopenia, and levels as low as 1x109/L have been documented . Additional laboratory tests that should be done are a full coagulation panel, fibrinogen, D-dimer, bilirubin, lactate dehydrogenase (LDH), haptoglobin, hematocrit, and a peripheral blood smear which is highly useful as well . Once a preliminary diagnosis is made, more advanced studies can be implemented in order to confirm the presence of drug-dependent antibodies (DDAs) . Various techniques are used, including enzyme-linked immunoassay (ELISA), flow cytometry and Western blotting (WB), to confirm the diagnosis   . However, due to the cost and the paucity of advanced laboratories with these methods throughout the world, drug-induced thrombocytopenia is often diagnosed based on clinical findings  .