Will any over-the-counter anti-inflammatory agents help with achilles tendonitis?

Yes: Some may help manage the symptoms but stretching is the most helpful to alleviate the problem.

Yes, sometimes: You may get some relief of pain and inflammation from otc nsaids. Topical nsaids may also help. I would suggest resting the area, use ice, lift the heel with a heel lift, and avoid exercises that may stress the achilles. A physician or physical therapist may be able to tape the foot in plantarflexion for immediate relief of pain.