Acetylsalicylic acid in the treatment of headache.

Acetylsalicylic acid (ASA) is used to treat a broad range of symptoms and disorders. Since its discovery in 1897, it has been used to treat fever and rheumatic pain, to inhibit the formation of thrombocytes, to prevent myocardial ischemia and strokes, and as preventive medication against neoplasms. ASA is best known, however, as a headache medication. For this function alone, ASA underwent an evolution: from powder to tablet to effervescent and chewable tablets. In addition to these oral formulations, an injectable form was developed in the 1970s for intravenous and intramuscular application. Furthermore, coated (slow-releasing) tablets are now used in the prophylactic treatment of migraine. The various forms of ASA used to treat headache are discussed and the controlled studies conducted to evaluate ASA's efficacy in headache treatment are summarized.