hops (Humulus lupulus, incl. spent brewing hops)

Hops (Humulus lupulus) are an unusual case: a dog-specific toxicity with an actual antidote, which makes it a true emergency. Phenolic compounds in hops are suspected to uncouple oxidative phosphorylation, producing a malignant-hyperthermia-like syndrome. In practical terms, the dog cannot stop generating heat and body temperature climbs out of control. No threshold dose has been established. Spent hops from a single home-brew batch have killed dogs, and the ASPCA Animal Poison Control Center reports rising incidence tracking the growth of home brewing. The exposures to know are spent hops dumped after brew day, hop pellets, and hop-containing supplements. The classic accident is a compost pile or backyard heap of wet spent hops that the dog finds hours later. Signs can begin within a few hours; the Merck Veterinary Manual describes onset at 8-24 hours lasting 24-48 hours. Expect severe hyperthermia, panting, rapid breathing, tachycardia, vomiting, diarrhea, agitation and lethargy, progressing to seizures and death. Greyhounds and other breeds susceptible to malignant hyperthermia may be at higher risk. Call your veterinarian or the ASPCA Animal Poison Control Center at 888-426-4435 immediately and say the word hops on the phone, because that is what prompts the clinic to have dantrolene ready. Treatment centers on dantrolene at 2-3 mg/kg IV (or 3.5 mg/kg orally, up to 10 mg/kg) plus active cooling, both of which happen in hospital. Do not induce vomiting at home.