Arachidonic acid has been found to be the major source of prostaglandins. Phospholipase A2 converts phospholipid to arachidonic acid as it is released from the cell membrane. The cyclooxygenase (COX) enzyme catalyzes the formation of prostanoids from arachidonic acids. During inflammatory responses, prostaglandin E2 (PGE2) has been the most closely associated prostanoid, and it is for this reason, that PGE2 presence is often considered an indicator of local COX activity. Although most nonsteroidal anti-inflammatory drugs (NSAIDs) are rapidly absorbed in their oral forms, the amount of drug absorption from the gastric tract is more important than the rate. Additionally, most members of this class of drugs are weak acids, maintain very good lipid solubility, and usually are highly bound to plasma proteins.