We have already blogged about the benefits of anti-platelet agents in stroke prevention.
We haven’t talked about how they work, or which one(s) are best.
Platelets are an important component of blood clotting (or hemostasis) – the normal process that stops us bleeding and facilitates healing after a cut or other injury:
This same platelet led coagulation cascade can lead to blood clot formation inside intact but diseased arteries laden with atheroma – the result of years of hypertension, high cholesterol and smoking:
These small blood clots then break off and travel down the artery causing (in the case of a cerebral blood vessel) a TIA or stroke.
There are three currently available anti-platelet medications – aspirin, modified release dipyridamole with aspirin (Aggrenox) and clopidogrel (Plavix) which inhibit platelet activation and aggregation.
Comparative studies have shown that all three drugs reduce the risk of ischemic stroke in high risk patients who have had a previous stroke or TIA. Aspirin is the cheapest of the three. Aggrenox is more effective than aspirin alone, but can cause troubling headache in some patients. Clopidogrel can be used in patients who are allergic or immune to aspirin.
Because these drugs work in different ways, investigators have asked whether combining them might be even more beneficial.
The initial studies said No. The MATCH (2004), CHARISMA (2006) and SPS3 (2012) trials all showed that long term use of the combination of aspirin and clopidogrel failed to reduce the risk of major vascular events and also led to significant increased life-threatening bleeding complications (mainly intracranial and gastrointestinal) compared with either drug alone.
However, new data from the CHANCE study presented at this year’s international stroke meeting shows that a short course of combined treatment might be helpful:
The study enrolled 5170 patients who had suffered a TIA or minor stroke within the previous 24hrs, randomly assigned to one of two treatment groups: The first group received aspirin (75-300 mg one-day loading dose followed by 75 mg/day). The second group received the same aspirin regimen plus clopidogrel (loading dose of 300 mg followed by 75 mg/day) for 21 days, then just the clopidogrel alone after that.
The study showed that the 90d stroke incidence was lower in those who received both aspirin and clopidogrel.
The risk of hemorrhagic stroke and other severe bleeding was the same in the two groups.
In other words, short term combination anti-platelet therapy might be more effective in preventing stroke in this high risk TIA and minor stroke group, and this is something we will be offering patients seen in Monmouth’s innovative TIA Rapid Evaluation Center.