increase in cholesterol, triglycerides, liver enzymes, and bleeding. Hematological Use of ticlopidine has been associated with neutropenia, thrombocytopenia, thrombotic thrombocytopenic purpura (TTP), and aplastic anemia. Because of this risk, patients who are started on ticlopidine are typically monitored with blood tests to test their cell counts every two weeks for the first three months. Pregnancy and lactation Ticlopidine is a FDA pregnancy risk category B. There have been no studies done in humans. Studies in rats show that high drug levels could cause toxicity in both mother and fetus, but there are no known birth defects associated with its use. There have been no studies to test whether ticlopidine goes into breast milk. Studies in rats have shown that it is passed in rats’ milk. Interactions Ticlopidine interacts with several classes of medications. It increases the antiplatelet effects of aspirin and other NSAIDs. Taking ticlopidine at the same time as antacids decreases the absorption of ticlopidine. Ticlopidine inhibits liver CYP2C19 and CYP2B6 and thus can affect blood levels of medications metabolized by these systems. Mechanism of action Ticlopidine is a thienopyridine which, when metabolized by the body, irreversibly blocks the P2Y12 component of the ADP receptor on the surface of platelets. Without ADP, fibrinogen does not bind to the platelet surface, preventing platelets from sticking to each other. By interfering with platelet function, ticlopidine prevents clots from forming on the inside of blood vessels. Anti-platelet effects start within 2 days and reach their maximum by 6 days of therapy. Ticlopidine’s effects persist for 3 days after discontinuing ticlopidine although it may take 1–2 weeks for platelet function to return to normal, as the medication affects platelets irreversibly. Therefore, new platelets must be formed before platelet function normalizes. Pharmacokinetics Ticlopidine is ingested orally with 80% bioavailability with rapid absorption. Even higher absorption can occur if ticlopidine is taken with food. It is metabolized by the liver with both renal and fecal elimination. Clearance is nonlinear and varies with repeated dosing. After the first dose the half life is 12.6 hours, but with repeated dosing the maximum half life is 4–5 days. Clearance is also slower in the elderly. The drug is 98% reversibly bound to proteins. Chemical properties Ticlopidine's systemic name is 5-[(2-chlorophenyl)methyl]-4,5,6,7-tetrahydrothieno[3,2-c]pyridine. Its molecular weight is 263.786 g/mol. It is a white crystalline solid. It is soluble in water and methanol and somewhat soluble in methylene chloride, ethanol, and acetone.