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PHARMACOLOGICAL ACTIVITIES - TOXICOLOGY - DRUG INTERACTIONS

Harpagophytum procumbens (Devil’s Claw)

Radix Harpagophyti is documented as a supportive treatment of degenerative rheumatism, painful
arthrosis and tendonitis (WHO, 2007). Research conducted on Radix Harpagophyti in the early
seventies indicated that the anti-arthritic activity of Radix Harpagophyti was due to the redox
potential of the iridoid glycosides (Beresford, 2002). Radix Harpagophyti is chondro-protective,
possibly due to inhibition of inflammatory mediators, including cyclooxygenase-2 (COX-2),
leukotrienes, nitric oxide, tumour necrosis factor-alpha, and interleukin-1beta. It is believed that
the analgesic action of Radix Harpagophyti may be due to a complex interaction between various
active principles, suggesting that these, especially harpagoside interfere with the mechanisms
which regulate calcium in the cells (Occhiuto et al., 1985). Radix Harpagophyti also has
antioxidant effects by scavenging both superoxide and peroxyl free radicals in a dose dependent
manner (Langmead et al., 2002).

Toxicity for Radix Harpagophyti has not been documented in dogs and cats when administered orally in
therapeutic doses. A purified extract of Radix Harpagophyti containing 85% harpagoside showed an acute oral
LD of 511 mg/kg of body weight in mice. The intraperitoneal LD of harpagoside in mice amounted to 1 g/kg of
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TOXICOLOGY male Wistar rats, no significant haematological or gross pathological findings were evident following 21 days of
body weight, whereas the LD of harpagide was greater than 3.2 g/kg of body weight in the same conditions. In
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sub-acute oral treatment with 7.5 g/kg of body weight of Radix Harpagophyti (EMEA, 2009). In male and female
Swiss Webster mice the acute oral LD of Radix Harpagophyti was >13.5 g/kg of body weight (ESCOP, 2009).
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Equivalent toxic dose in 20 kg dog: >270 g PO of Radix Harpagophyti.
Equivalent toxic dose in 5 kg cat: >67.5 g PO of Radix Harpagophyti.

DRUG Validated interactions studies do not exist for Radix Harpagophyti preparations. Clinical
INTERACTIONS interactions with other drugs have not been reported. However, additive pharmacodynamic
anti-inflammatory effect of Radix Harpagophyti enables reduced drug dose and a reduction in
drug adverse effects for a range of NSAIDs (Stargrove, et al. 2008).

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