Amantadine for Chronic Pain

Uses/Indications:

Amantadine may have efficacy and clinical usefulness against some veterinary viral diseases, but presently the greatest interest for its use in small animals is as an NMDA antagonist in the adjunctive treatment of chronic pain, particularly those tolerant to opioids. Amantadine antagonizes the N-methyl-D-aspartate (NMDA) receptor, and chronic pain can be maintained or exacerbated when glutamate or aspartate bind to this receptor. This receptor is important in allodynia (sensation of pain from a non-noxious stimulus), therefore in combination with other analgesic (e.g. opiates, NSAIDs) is can help alleviate chronic pain.

–    Treatment of arthritis pain

–    Treatment of neurologic pain

–    Treatment of pain associated with cancer

–    Treatment of pain associated with surgery

Study:

In a randomized, blinded, and placebo-controlled study with parallel groups (days 21-42), 31 dogs treated with an NSAID with continued pelvic limb lameness were studied over 42 days when given an adjunctive dose of amantadine. On day 0, analgesic medications were discontinued. On day 7, all dogs received meloxicam for 5 weeks. On day 21, all dogs received amantadine (3–5 mg/kg once daily) or placebo for 21 days, in addition to receiving meloxicam. Assessments were performed before the study and on days 7, 21, and 42 using a client-specific outcome measures (CSOM). For CSOM activity, there was a significant time by treatment effect (P = .009). On the basis of the planned post hoc t-tests of post-randomization means, there was a significant difference between treatment groups on day 42 (P = .030), with the amantadine group being more active.

Adverse Effects for Dogs & Cats:

Agitation, loose stools, flatulence or diarrhea, usually experienced early in therapy.

Dosing:

(As adjunctive therapy for chronic pain in dogs & cats.)

Approximate dose: 3 – 5mg/kg PO once daily

Monitoring Parameters:

Adverse effects (GI, agitation), Efficacy