Clopidogrel

What it is

Clopidogrel is an antiplatelet drug. It is a prodrug converted in the liver into an active form that irreversibly blocks the P2Y12 receptor on platelets, so they clump together far less readily for the rest of their lifespan. It is used to prevent clots in arteries, including after stenting and for stroke prevention.

A usual adult range, not a national label — the dose and the timing differ by country and by product.

Used for

• Thrombosis
• Stroke prevention

Approved uses differ by country — some of these may be off-label or unapproved where you live.

What to know while taking it

Food does not matter, but continuity does, since the effect fades only as new platelets are made. Bleeding risk is the main trade-off, and it rises further with acetylsalicylic acid, a combination sometimes prescribed deliberately and sometimes not; anticoagulants such as warfarin alongside it are generally avoided. Omeprazole and esomeprazole inhibit the enzyme that activates clopidogrel and can blunt its effect, so another stomach drug is often chosen instead. Hemoglobin and platelets are checked to catch quiet blood loss, and any surgeon or dentist should be told about the drug before a procedure.

When to see a doctor

Black or bloody stools, blood in vomit or urine, bleeding that will not stop, or sudden severe headache after a knock to the head all mean seeing a doctor without delay.

Worth knowing

• Raises bleeding risk
• Tell the surgeon before any operation

Markers to watch

• Hemoglobin
• Platelets