A method of detecting an activity of a COX-2 enzyme in a subject that includes obtaining a sample of the subject; detecting an amino acid eicosanoid metabolite in the sample, wherein the presence of the amino acid eicosanoid metabolite indicates the activity of the COX-2 enzyme of the subject. Preferably the amino acid eicosanoid metabolite is a PGH.sub.2-Gly or HETE-Gly metabolite. The metabolite may be detected based on metabolism of a COX-2-selective substrate. Preferably, the substrate is a lipoamino acid. More preferably, the lipoamino acid is selected from NAGly, N-arachidonyl-alanine, and .delta.-arachidonyl aminobutuyic acid.
