What are the side effects and interactions of antiplatelet drugs?
There are numerous forms of antiplatelet drugs and they all work in a similar fashion, although there are also drug interactions and side effects associated with these forms of medication. In the case of aspirin, it has been speculated that when it is taken in conjunction with ibuprofen that it may inhibit its antiplatelet effect. Also, when taken with anti-coagulants, it may further increase this effect, putting the patient at an increased risk of bleeding. This bleeding is a key adverse effect of aspirin. Due to this, it is only given to those where a benefit outweighs the risk, such as those with CVD and in stroke prevention. Also, to prevent GI bleeding, the maximum dose given is 75mg, which is the dose that maximum platelet inhibition will be achieved. Also, it is not given in children since this may result in Reyes syndrome.
In the case of Dipyridamole, it has been found that antacids may reduce the efficacy of it, thereby causing a reduction in ant-platelet effect. Also, like aspirin, when given in conjunction with anticoagulants it may further increase their effect. It can also further increase the effect of antihypertensives, in some cases to the extent that it can result in hypotension. In terms of adverse effects, 4/10 patients will stop taking it due to the severe headaches that it causes. Also, it can cause flushing, vomiting, nausea and diarrhoea. It may also initiate a hypersensitivity reaction, resulting in bronchospasm, urticaria and also rash.
With Clopidogrel, it should be used with caution in those receiving Gp IIb/IIIa inhibitors and oral anticoagulants are not recommended in conjunction with it since it may make any bleeding more intense. Linked to this is the use of NSAIDs which increased the risk of blood loss. However, it is not clear if this is with all NSAIDs, and as a result they should be used with caution. With regard to side effects, these range from common to rare.
Common side effects include bruising, dyspepsia (which may prompt the patient to take antacids, however this will not interfere with its antiplatelet activity unlike dipyridamole), GI bleeding, nausea, diarrhoea, and also haematoma. Rare side effects include vertigo, neutropenia and also taste disturbances. Uncommon side effects include intracranial haemorrhage, eye bleeding and also gastric and duodenal ulcers. There was a newer drug released called Ticlopide, however, this caused a severe reduction in platelets as well as it resulting in agranulocytosis.