With the rising popularity of home brewing, hops ingestion and toxicity in dogs is becoming more common in the ER. Ingestion of hops in dogs causes malignant hyperthermia, however the mechanism of action is unknown. The toxic component of the plant is also unknown, but essential oils, resins, phenolic compounds or nitrogenous constituents have been considered. Toxicity can occur from both raw and spent hops.
Body temperature often exceeds 105°F in cases of hops ingestion. Additional signs of hops toxicity in dogs include tachycardia, tachypnea, panting, anxiety, vomiting and abdominal pain. Myoglobinuria may be seen. Electrolyte abnormalities include hyperkalemia, hypercalcemia, hyperphosphatemia, and hypermagnesemia. Other labwork findings include elevated CK, elevated liver enzymes, azotemia and metabolic acidosis. More severe cases may progress to coagulopathy/DIC. Death can occur within 6 hours of ingestion and onset of rigor mortis is rapid. Breeds predisposed to malignant hyperthermia may be more susceptible to toxicity: Greyhounds, Labrador Retrievers, Golden Retrievers, Saint Bernards, Pointers, Dobermans, Border Collies, English Springer Spaniels, and northern breeds.
Treatment of hops toxicity is aimed at treatment of malignant hyperthermia and its sequelae. Emesis should be induced in asymptomatic patients within 1-2 hours of ingestion. IV fluids should be administered. Cooling measures may be performed as with heat stroke (see Tip #2). Additional supportive care may include antiemetics, analgesics and sedatives.
Dantrolene is a skeletal muscle relaxant used in the treatment of malignant hyperthermia. It antagonizes ryanodine receptors in skeletal muscle, thus inhibiting the release of calcium ions from the sarcoplasmic reticulum and ultimately inhibiting muscle contraction. The dose is 2 - 3 mg/kg IV or 3.5 mg/kg PO q8-12h. Cyproheptadine has also been suggested in treating hops toxicity, however there is no evidence for its effectiveness. NSAIDs and steroids should not be used in the treatment of malignant hyperthermia.