Drug-induced thrombocytopeniaThrombocytopenia:Thrombocytopeniais any disorder in which there is an abnormally low amount(below 100,000cells/mm3) of platelets. Platelets are parts of the bloodthat help blood to clot. Drug-Induced Thrombocytopenia:When a drugs causesreduction in platelet count, it is called drug-induced thrombocytopenia.
Types of Drug-Induced Thrombocytopenia:Ø Drug-induced immune thrombocytopenia.Ø Drug-induced nonimmune thrombocytopenia.Drug-inducedimmune thrombocytopeniaDrug causesproduction of antibodiesand destroys the platelets, due to immunological reaction leading to drug-inducedimmune thrombocytopenia. Heparin causes drug-induced immune thrombocytopenia inmost of the cases. Mechanism :Hapten typereactions:The offendingdrug binds covalently to certain platelet Glyco Proteins (GPs).
Antibodies aregenerated that bind to these drug-bound GP epitopes. After the binding ofantibodies to the platelet surface, lysis occurs through complement activationor through clearance from the circulation by macrophages. Hapten-mediatedimmune thrombocytopenia usually occurs at least 7 days after the initiation ofthe drug, although it can occur much sooner if the exposure is actually areexposure to a previously administered drug.Antibody binding:Antibodies existin the blood that recognize an epitope on the platelet GP.( Quinine,anticonvulsants, vancomycin and nonsteroidal anti-inflammatory)Immunecomplex:Most serioustype of heparin-induced thrombocytopenia (HIT) type II is by formation ofimmune complex. Types: HITtype I: More common, mild, reversible, non-immune-mediated reaction that usually occurs within the first2 days of therapy, often asymptomatic.
HIT type II:Less common butmore severe and more complicated. The platelet count generally begins todecline 5 to 10 days after the start of heparin therapy. Patients undergone a recent surgery , patients receiving heparinfor thrombosis prophylaxis, cardiac surgery, orthopedic surgery are at highrisk. Diagnosis of HIT:Clinical basedand supported by laboratory testing. Several types of assays are availableplatelet activation assays, platelet aggregation studies and enzyme-linked immunesorbent assay method. Drug-induced non-immune thrombocytopenia:Drug causesdirect toxicity or bone marrow suppression. Chemotherapy drugsand antiepileptic drugs cause drug-induced non-immune thrombocytopenia. Symptoms:Decreased PlatletsAbnormalbleedingBleeding whenyou brush your teethEasy bruisingPinpoint redspots on the skin (petechiae) Treatment:Stop the offending drug and treat symptomatically.
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For people who havelife-threatening bleeding, treatments may include:Immunoglobulin therapy (IVIG) Plasma exchange (plasmapheresis)Platelet transfusionsCorticosteroidsReferences:Kamakshi V. Rao.Drug-Induced HematologicDisorders: Pharmacotherapy: A Pathophysiologic Approach. Joseph T. DiPiro, etalhttps://medlineplus.gov/ency/article/000556.htmBy:K.Bharathi Priya Assistant Professor Department of Pharmacy Practice