THE MERCK VETERINARY MANUAL
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Herbal Supplements (Toxicity)

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Ma Huang (Ephedrine) and Guarana (Caffeine)

Several herbal supplements, sold with the claim of providing weight loss and energy, contain guarana (Paullinia cupana), a natural source of caffeine, and ma huang (Ephedra sinica), a natural source of ephedrine. The amount of ma huang and guarana present in herbal products may vary considerably (labels should be read for amounts). In people, use of herbal supplements containing guarana and ma huang have been linked to acute hepatitis, nephrolithiasis, hypersensitivity myocarditis, and sudden death. In dogs, accidental ingestion of herbal supplements containing ma huang and guarana can have synergistic effects when ingested together and can lead to severe hyperactivity, tremors, seizures, vomiting, tachycardia, hyperthermia, and death within a few hours of exposure. The use of ephedra-containing supplements has been banned by the FDA. For treatment, see Pseudoephedrine and Ephedrine.

5-Hydroxytryptophan

Several OTC herbal supplements containing 5-hydroxytryptophan (5-HTP) or Griffonia seed extracts claim to treat depression, headaches, insomnia, and obesity. Orally, 5-HTP is rapidly absorbed and constitutively converted to serotonin (5-hydroxytryptamine). In cases of 5-HTP overdose, excessive concentrations of serotonin at target cells (GI, CNS, cardiovascular, and respiratory systems) can lead to a serotonin-like syndrome in dogs (eg, seizures, depression, tremors, ataxia, vomiting, diarrhea, hyperthermia, transient blindness, and death). Clinical signs can develop within 4 hr after ingestion and last up to 36 hr. Treatment consists of early decontamination, control of CNS signs (diazepam, barbiturates, phenothiazines such as acepromazine or chlorpromazine), thermoregulation (cool water bath, fans), fluid therapy, and administration of a serotonin antagonist such as cyproheptadine (1.1 mg/kg, PO or rectally for dogs, and 2–4 mg per cat, once or twice at an 8-hr interval).

Last full review/revision August 2014 by Safdar A. Khan, DVM, MS, PhD, DABVT

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