For example, the mechanism of action of aspirin involves irreversible inhibition of the enzyme cyclooxygenase, therefore suppressing the production of prostaglandins and thromboxanes, thereby reducing pain and inflammation. However, some drug mechanisms of action are still unknown. For example, phenytoin is used to treat symptoms of epileptic seizures, but the mechanism by which this is achieved is still unknown, despite the fact that the drug has been in use for many years.