Which compound is the active ingredient in aspirin?

The active ingredient in aspirin is acetylsalicylic acid.

Acetylsalicylic acid, often abbreviated ASA, is an organic compound with the formula C₉H₈O₄. It belongs to the salicylate family and is used for pain relief, fever reduction, and inflammation. At low doses, under medical guidance, it can also reduce platelet aggregation and help prevent certain cardiovascular events.

The modern drug was developed from earlier observations about willow bark and salicylates. In 1897, Felix Hoffmann at the Bayer company prepared acetylsalicylic acid in a form suitable for pharmaceutical use. The brand name Aspirin became widely associated with the compound.

Aspirin is not interchangeable with all pain relievers. Ibuprofen belongs to a different chemical class, while paracetamol has different pharmacological properties. Aspirin can cause stomach irritation and is generally avoided in children with viral illnesses because of the risk of Reye’s syndrome.