Clopidogrel

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Clopidogrel is a blood-thinning agent that can be used to prevent a heart attack or stroke and to treat circulatory disorders in the limbs (peripheral arterial disease). It is considered to be well tolerated, and its effectiveness is comparable to that of other "blood thinners". However, clopidogrel is significantly more expensive, which is why the active ingredient is only used as a second-choice agent. Here you can read everything you need to know about clopidogrel.

This is how clopidogrel works

Mechanism of action

The human body has an efficient system for closing wounds, which is activated immediately as soon as the smallest injuries occur. The blood platelets (thrombocytes) accumulate to form clots and close the open area so that no more blood can escape. For this wound closure, certain endogenous substances (including the so-called adenosine phosphate, ADP) are required, which signal the injury to the blood platelets and thus stimulate them to collect.

Patients who have already had a heart attack or who suffer from circulatory disorders in the limbs are often at risk of blood clots (thrombi) forming on the inner wall of the blood vessels. If these are carried away by the bloodstream, they can clog blood vessels in the brain or heart as so-called embolus, thus causing a (renewed) heart attack or stroke.

Clopidogrel can be given to reduce this risk. As a so-called platelet aggregation inhibitor, it prevents the blood platelets from accumulating quickly by blocking the transmission of signals to the blood platelets by the messenger substance adenosine phosphate. This prevents the blood from clotting too quickly. As a result, Clopidogrel efficiently reduces the risk of a heart attack or stroke.

Uptake, breakdown and excretion of clopidogrel

When taken by mouth, only about 50 percent of clopidogrel is absorbed from the intestines into the blood. Then the active ingredient has to be activated in the liver before it can take effect. The breakdown takes place in the liver; the breakdown products are excreted via the kidneys and stool.

When is clopidogrel used?

The areas of application (indications) of clopidogrel are:

• a heart attack seven to 35 days ago
• Circulatory disorders of the limbs (peripheral occlusive disease)

This is how clopidogrel is used

The active ingredient clopidogrel works for a relatively long time and therefore only needs to be taken once a day. This is usually done via tablets and regardless of meals. The usual daily dose for adults is 75 milligrams. Treatment is often started with a single "loading dose" of 300 milligrams of clopidogrel and then continued with 75 milligrams daily.

It can be useful to combine clopidogrel with other drugs to intensify the effect. It is often combined with acetylsalicylic acid. The two active ingredients have different points of attack in the inhibition of blood coagulation, which delays the agglomeration of blood platelets even more efficiently. This combination of active ingredients is often prescribed to patients after a so-called "stent" has been inserted. A stent is a small tube that ensures unimpeded blood flow in narrow blood vessels when a patient is at increased risk of heart attack or stroke.

What are the side effects of clopidogrel?

Often (that is, in one to ten percent of those treated), clopidogrel causes side effects such as bruising, bleeding in the gastrointestinal tract and general gastrointestinal complaints such as diarrhea and abdominal pain. Less than one percent of those treated, changes in the blood count (lack of platelets or leukocytes, increase in eosinophilic granulocytes), cerebral haemorrhage, headache, numbness, dizziness, drowsiness, eye bleeding, gastrointestinal ulcers Skin symptoms, blood in the urine and bleeding time prolonged.

What should be considered when taking clopidogrel?

Contraindications

Patients with severe liver dysfunction or acute abnormal bleeding should not take clopidogrel.

limitations

The clopidogrel effect lasts for several days. Therefore, in the case of planned operations (including dental operations), the active ingredient should be discontinued one week in advance in consultation with the doctor.

Patients with impaired kidney or liver function should consult their doctor before taking clopidogrel, as very little data have been collected on this.

Some people are called slow metabolisers of CYP2C19. With them, the active ingredient is only activated more slowly in the liver, which significantly reduces its effect. Certain tests can help predict how effective clopidogrel will be.

Interactions

The effects and side effects of clopidogrel are aggravated by other blood thinning agents (such as acetylsalicylic acid, heparin, abciximab, eptifibatide, tirofiban). The same goes for pain relievers like ibuprofen, naproxen, diclofenac, indomethacin, meloxicam, piroxicam, phenylbutazone, celecoxib, parecoxib, and etoricoxib.

Medicinal substances that reduce the activation of clopidogrel reduce its blood-thinning effect. These drugs include, for example, omeprazole (stomach acid inhibitor), fluoxetine and moclobemide (antidepressants), voriconazole and fluconazole (for fungal infections), ticlopidine (also an anti-platelet inhibitor), ciprofloxacin and chloramphenicol (antibiotics), cimbretidine (for stomach ulcers), and carbamazepine (for epilepsy).

Overdose

An overdose of clopidogrel can lead to a severe bleeding tendency. Therefore, a doctor should always be consulted if an overdose is suspected.

So far, there is no known antidote for poisoning with clopidogrel. One treatment option is the administration of canned platelets to restore blood clotting.

Age restrictions

The active ingredient clopidogrel must not be used in children and adolescents, as it has not been proven to be effective.

pregnancy and breast feeding period

Pregnant and breastfeeding women should only take the active ingredient clopidogrel after the doctor has carefully weighed the benefits and risks of the treatment against each other.

How to get medication with clopidogrel

Since regular examination by the attending physician is recommended for "blood-thinning" therapy, drugs containing clopidogrel require a prescription.

How long has clopidogrel been known?

Clopidogrel has not been known as an active ingredient for very long. It intervenes in the blood coagulation at a different point than the otherwise so often used blood-thinning agents such as acetylsalicylic acid (ASA). Gastrointestinal ulcers as side effects of treatment are less common with clopidogrel than with ASA. In studies, however, it was found that the active ingredient has the same effectiveness as its "counterparts", but at the same time is significantly more expensive. Therefore, clopidogrel is only used as a second choice, for example when intolerance to the first choice is to be expected.

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