This mechanistic, proof of concept laboratory study will test the pharmacological properties of diclofenac in individuals with AUD. Participants will complete two sessions in which they will receive a single dose of diclofenac (100 mg) or matched placebo in a randomized and double blind fashion. The primary aim is to assess whether this dose of diclofenac, vs. placebo, increases circulating levels of kynurenic acid. This finding would provide evidence that diclofenac (100 mg) inhibits the kynurenine 3-monooxygenase enzyme.