Posted: Dec. 14, 2020
Harpagoside is a glycoside derived from the Devil’s Claw plant (Harpagophytum procumbens). It is a non-steroidal anti-inflammatory drug that inhibits COX-1 and COX-2, similar to phenylbutazone. There are no FDA-approved harpagoside-containing products.
To the extent that Devil’s Claw products exist, they are manufactured absent regulatory oversight—with unknown safety, efficacy, stability, and purity. Harpagoside is assigned a 4/B classification in the Association of Racing Commissioners International Uniform Classification of Foreign Substances, consistent with other NSAIDs lacking FDA approval.
The detection of harpagoside in a post-race sample can result in a horse’s disqualification, a fine, and suspension for the trainer. Devil’s Claw products are marketed in a variety of over-the-counter formulations as herbal remedies for a range of conditions including arthritis, fever, and muscular pain.
Harpagoside content can be highly variable from one product to the next, as well as from batch to batch for a single product. Additionally, the amount of harpagoside may differ substantially from that declared on the label contents. For these reasons, there is no reliable withdrawal guidance for the use of these products.
Further, labels may not clearly indicate the presence of harpagoside or Devil’s Claw but simply refer to a “proprietary blend of herbs” so the end-user may be unaware that the product contains a prohibited substance.
The Devil’s Claw plant is indigenous to southern Africa, growing in dry sandy soil; it is not native to North America and is not a constituent of bedding, forage or hay. Therefore, the introduction of Devil’s Claw, or its derivatives, into a horse’s environment can be prevented by common sense hygiene practices and stable management.
Horsemen are advised to exercise caution in using these products in proximity to a race. Should a veterinarian determine harpagoside treatment is warranted for a specific patient, clearance testing is recommended.