Known brand names include Plavix.
An oral antiplatelet drug that keeps platelets from clumping. It lowers the risk of heart attack and stroke after acute coronary syndrome, a recent heart attack or stroke, or with peripheral artery disease.
Clopidogrel is inactive until liver enzymes, mainly one called CYP2C19, change it into its working form. The working form locks onto the P2Y12 receptor on platelets, which normally responds to a chemical signal called ADP. With that receptor blocked, platelets cannot switch on and clump together. The binding is permanent, so a blocked platelet stays blocked for the rest of its life, about 7 to 10 days.
Some effect on platelets shows up within 2 hours of a single dose, and with daily doses it builds to a steady level between day 3 and day 7. After it is stopped, platelet clumping and bleeding time slowly return to normal, usually in about 5 days. With platelets less able to clump, clots are less likely to form in narrowed arteries, but bleeding becomes more likely. People whose CYP2C19 enzyme barely works make less of the working form and get less protection, and a gene test can identify them.
Clopidogrel is a pill that keeps platelets, the blood cells that clump together to form clots, from sticking together. Its goal is to lower the chance of a heart attack or stroke. Together with aspirin, it is used in people having a heart attack or a type of severe chest pain called unstable angina. It is also used by people who recently had a heart attack or stroke, or who have peripheral arterial disease, poor blood flow in the arteries to the legs.
It is a tablet taken by mouth with or without food, and it protects the heart and blood vessels only for as long as it is taken. Stopping it early raises the risk of a heart attack or stroke, and of a clot forming inside a stent. Its safety and benefit in children have not been shown.
Bleeding is the most common side effect: bruising, nosebleeds, and blood in the urine. Itching, rash, diarrhea, taste changes, and headache can also happen. The label treats major bleeding as dangerous, along with a rare blood clotting disorder called TTP, serious blood and skin reactions, a rare cause of severe low blood sugar, and heart attack, stroke, or a clotted stent after stopping it too early.
This is the boxed warning, the warning the FDA label prints first.
Reduced effect in CYP2C19 poor metabolizers. Clopidogrel works only after CYP2C19 converts it to its active form. Patients with two loss-of-function CYP2C19 alleles make less active metabolite and get less platelet inhibition. Genetic tests can identify them; consider another P2Y12 inhibitor for these patients.
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