Chocolate toxicity in pets

With Halloween approaching, the criticalists at NorthStar VETS thought this would be a good time to pool their collective experiences and offer some suggestions for managing dogs that ingest chocolate. The tips and points provided below are as much based on their experiences in various settings treating many affected dogs, as what may be found in texts and citations. With that, they hope some of the information below will be helpful to you.

Understanding chocolate toxicity in pets

• In most chocolate compounds, theobromine is the predominant toxic compound, with methylxanthines and caffeine present in much lower concentrations.
• It is not always clear how much or what kind of chocolate a pet consumed after-the-fact. For animals that ingested chocolate from home-made products or from bakeries, it is especially difficult to identify the exact amount of chocolate used.
• The Veterinary Information Network (VIN) provides easy-to-use calculators to determine if a pet consumed a toxic amount of chocolate. There are excellent tables and calculators available for smart phones, as well. Regardless, using good clinical judgment, assessing each patient individually and often is more important than trying to forecast what signs to expect and when. As with other intoxications, there is lots of interpatient variability. We become concerned about toxicity and likely need for inpatient observation when dogs eat more than 2 oz/kg of milk chocolate.

Diagnosing chocolate toxicity in pets

• While not something to share with every client, chocolate ingestion is seldom fatal if pets are treated symptomatically, appropriately and aggressively, even when early decontamination is not possible. When dogs succumb, it is generally due to arrhythmias, respiratory failure, or severe pancreatitis.
• Typically, chocolate produces marked emesis such that the actual exposure is less than what the dog actually ate.
• EXCEPTION: YOUNG LAB RETRIEVERS and the like!
• If they do vomit, they will often eat it if not careful.
• Almost all dogs will become mildly symptomatic 2-3 hours after ingestion.
• Initial clinical signs (observed within 6-8 hours after ingestion): polydipsia, restlessness, vomiting and diarrhea.
• Polyuria, tremors, tachycardia, tachypnea, hyperthermia, arrhythmias are generally seen after 8-12 hours.
• If a client suspects chocolate ingestion, and no signs are observed six hours after suspected exposure, it is unlikely this dog will become sick.
• Some intoxicated dogs will have “paradoxic” signs, e.g.
  miosis, sedation, bradycardia – Absence of classic signs does not rule out exposure.
• Because of high fat content of many chocolate products, pancreatitis may develop 24-48 hours following ingestion.

Treating chocolate toxicity in pets

• In general 3% hydrogen peroxide is the only product we occasionally advise for “at home” emesis induction. Salt and ipecac are not recommended. 1 ml/lb, up to a maximum of 45 mls (3 tablespoons) may be given safely.
• Outdated peroxide (flat, not fizzing) will not work. Peroxide may be mixed with a small amount of peanut butter, yogurt or vanilla ice cream without compromising efficacy.
• Peroxide is more likely to work if the dog is walked after it is given versus sitting in one place after administration.
• Apomorphine (dogs only) may be given in-hospital, either IV or conjunctival. In rare cases when marked sedation is observed, naloxone will reverse depression induced by apomorphine, but may actually exaggerate the vomiting. This is not ideal, as repeated vomiting will cause further dehydration in an already compromised pet. Bottom line: try not to reverse unless the pet is obtunded or hypoventilating.
• Typical apomorphine IV doses are 0.03 to 0.04 mg/kg.
• Xylazine (0.44mg/kg) IM is the emetic of choice in cats (for which chocolate ingestion is admittedly rare).
• Consider prescribing maropitant (Cerenia) or dolasetron (Anzemet) after emesis has been successful to help with patient comfort, without the risks associated with naloxone as noted above.
• Theobromine has a long half-life and undergoes entero-hepatic recirculation. Thus, repeated doses of activated charcoal (AC) are given. Recommendations vary, but we give 1-2 g/kg (~5 ml/lb of Toxiban) every 4-6 hours (while symptomatic), almost never needing to be given after 24 hours following ingestion. Most activated charcoal suspensions are available with and without cathartic.
• A generally safe rule of thumb (that may be applied to most, though not all intoxications) is to give AC with a cathartic (e.g. sorbitol or MgSO4) for the first dose, then AC WITHOUT a cathartic for subsequent doses.
• While acepromazine is not an anxiolytic in the dog, it appears to be very effective for managing the marked agitation observed with this toxicity. We do not give acepromazine in rare cases when seizures occur. We prefer to manage seizures in this setting with a constant rate infusion of benzodiazepine, such as diazepam. Propofol is also reasonable, but its use requires uninterrupted patient observation (for apnea).
• Barbiturates are likely effective but currently not available.
• Muscle tremors often respond to methocarbamol. If the injectable form is not available or IV access is not possible, tablets can be crushed and given per rectum.
• Try to avoid aggressive cooling measures in hyperthermic dogs, such as cold water baths.
• We do not treat modest tachycardia; however a heart rate > 160 beats/min in a dog with associated symptoms should probably be treated. Some sources advise using metoprolol, or other seldom prescribed anti-arrhythmics not stocked in most practices. Propranolol, to effect, is acceptable, and can be given rectally if other access not available.
• Theobromine accumulates in urine and can be re-absorbed through the bladder wall. Thus, dogs should be walked hourly. If recumbent, place a urinary catheter and evacuate the bladder hourly or continuously (closed collection system).

NorthStar VETS criticalists and emergency veterinarians are always happy to speak with you if you have concerns about any of your patients – please call us – we don’t bite – not even at Halloween!

Reid Groman, DVM, DACVIM, DACVECC
Diplomate, American College of Veterinary Emergency and Critical Care
Originally from Long Island, NY, Dr. Groman received his veterinary degree from Colorado State University in 1994. After completing an internship at Texas A&M University, he worked in general practice for two years only to return to the university to complete a residency in internal medicine in 2000. Because of his love of learning, Dr. Groman then went on to pursue and complete his residency in emergency medicine at the University of Pennsylvania in 2003. His passion for kidney disease led him to a fellowship in renal medicine and hemodialysis at the University of California-Davis in 2003.

Prior to joining NorthStar in October 2010, Dr. Groman spent eight years on clinical faculty at the University of Pennsylvania, where he remains an adjunct clinical assistant professor helping to mold future veterinarians. Dr. Groman is active on several committees within ACVIM and ACVECC. His professional interests include acute kidney disease, extracorporeal therapies, and general emergency medicine. Outside of work, Dr Groman likes golfing, hiking, and traveling with friends and family.

Joshua Portner, DVM, DACVECC
Diplomate, American College of Veterinary Emergency and Critical Care
Dr. Portner grew up in Southern New Hampshire. He obtained his bachelor’s degree in Biology/All-College Honors from Canisius College in Buffalo, New York, and his veterinary degree from Tufts University School of Veterinary Medicine in Massachusetts in 2004. After graduation from Tufts University, Dr. Portner completed a rotating internship in small animal medicine and surgery at Alameda East Veterinary Hospital in Denver, Colorado, and went on to complete his residency in Emergency and Critical Care at Ocean State Veterinary Specialists in Rhode Island in July of 2008. In 2009, Dr. Portner passed the specialist certification examination and became board certified in Emergency and Critical Care Medicine.

Dr. Portner has special interests in mechanical ventilation, nutrition for critical patients, and transfusion medicine. Along with membership in the Veterinary Emergency and Critical Care Society (VECCS), American Veterinary Medical Association (AVMA), and the New Jersey Veterinary Medical Association (NJVMA), he has also been a member of the International Veterinary Academy of Pain Management (IVAPM) and the International Sled Dog Veterinary Medical Association (ISDVMA), as well as several state associations. During his residency, he was a member of the Rhode Island Disaster Response Team, which is an organization responsible for providing medical care to sick and injured animals during a state of emergency.

Dr. Portner joined the NorthStar VETS team in November of 2008. He is currently an active member of the Policy and Procedure Comittee and runs the Blood Donor Program for the hospital. Dr. Portner has led several lectures for technicians and doctors in the hospital, as well as for members of our referral community. Most recently, he has become a member of the hospital’s Infection Control Comittee and was the lead team member during the control of a canine influenza outbreak in the central NJ region. Dr. Portner is currently working on a few publications for veterinary journals, one of which is expected to be published in 2010. In his spare time, he keeps busy by building furniture, playing indoor soccer, shooting archery, and going to the movies.