Beta-blockers Poisoning in Dogs

Beta-blockers are used for heart disease in the regulation of blood pressure in humans. They are also prescribed to dogs to regulate the heartbeat; however, it is prescribed carefully by veterinarians. When an overdose occurs by a dog, heart failure and kidney failure can ensue. Beta-blockers decrease the workload of the heart by altering the response to nerve impulses, and an overdose can very quickly lead to adverse effects.

Propranolol is a common beta-blocker that is successful in blocking the beta-1 and beta-2 receptors, known as norepinephrine and epinephrine. These receptors are responsible for the elevation of the heart rate during stressful situations. Beta-blockers decrease the heart rate, thus the amount of oxygen required for the cardiovascular system to work properly.

Propranolol can negatively interfere with other medications. It is important to only have this beta-blocker prescribed under a veterinarian’s care, as the veterinarian is aware of the other medications the dog is taking. Anesthetic agents, thyroid medications, hydralazine, cimetidine, insulin, lidocaine, and antacids are some of the medications that can interfere with propranolol.

Beta-blockers poisoning in dogs is a result of dogs ingesting human beta-blocker medication, such as propranolol, or overdosing on a beta-blocker medication that has been prescribed to them.

Beta-blockers can poison a dog very rapidly and it only takes a small amount to do so. Symptoms of beta-blocker poisoning in dogs include:

• Vomiting
• Nausea
• Decreased heart rate
• Lethargy
• Weakness
• Slow breathing
• Slow heart rate
• Seizures
• Collapse

Types

Propranolol can also be referred to a beta-blocker with another name. If your dog has ingested a beta-blocker medication prescribed to you, it is important to know the other names of these types of medications. Alternate names include:

• Heart medication
• Esmolol
• Nadolol
• Sotalol
• Metoprolol
• Timolol
• Carvedilol
• Atenolol
• Generic cardiac medication
• Generic blood pressure medication

Causes of beta-blocker poisoning in dogs occurs when dogs overdose on human beta-blocker medication, or are given an overdose of their own medication. Causes of the toxicity within the dog’s systems include:

• Negative chronotropic and inotropic actions affect the cardiovascular system
• The rapid blocking of adrenergic receptors
• Depression of the central nervous system

A very small amount of beta-blocker overdose can quickly result in toxicity. If your dog has overdosed on beta-blockers, call your veterinarian immediately. The veterinarian will perform a physical examination, including blood work, a biochemistry profile, and urinalysis. The veterinarian will be checking the blood potassium levels, as well as the blood glucose and plasma levels. The serum electrolyte levels will also be tested.  The physician will also come to a definitive diagnosis by observing the clinical signs, as he is aware that treatment must begin very quickly in order for the dog to survive.  It is important to communicate with the veterinarian the type and amount of medication the dog ingested.

The veterinarian will perform an electrocardiogram to check the heart rate and function in order to determine a slowed heartbeat, severe low blood pressure, and any other symptoms that may be associated with an overdose of this type of medication. The ECG will be a vital tool in diagnosing an overdose of beta-blockers, and when combined with the clinical signs, the veterinarian will be able to diagnose the situation.

It is very important that treatment be started immediately to help reverse the effects of the poisoning. Treatment methods include:

Decontamination

Gastric lavage, a procedure used to flush out the toxins that were ingested, may be performed. This will also be followed up with the use of activated charcoal to help absorb any of the toxic substance. Vomiting may be induced in place of gastric lavage, and this depends on the amount ingested and what the veterinarian feels is necessary.

Monitoring

The veterinarian will closely monitor the dog’s blood pressure and heart rate. He will also monitor the bloodwork on a regular basis.

IV fluids

Intravenous fluids will be given to keep the dog hydrated and to help excrete the substance during urination. Intravenous fluids are also very helpful to stabilize the electrolyte levels and to help the kidneys continue to function properly. Calcium can also be given intravenously, and has been proven to increase the amount of calcium in the cells. Once the calcium is released into the cytoplasm of the dog, blood pressure can stabilize, cardiac output can strengthen, and inotropy can occur. 

Insulin

In severe cases of beta-blocker toxicosis, insulin therapy may be given. This type of treatment option has recently emerged as being quite effective in treating severe beta-blocker toxicity. In some cases, IV lipid emulsion therapy is also used.

If the dog was able to receive immediate treatment, and the dosage level was not too high, the prognosis is fair to good. Unfortunately, an overdose of beta-blockers can prove fatal in many cases. If your dog has survived treatment, your veterinarian may want to keep him for at least 24 hours to monitor his system. More than likely, your dog may be hospitalized for longer periods if he is stabilized and responding to treatment.

Once you bring your dog home, the veterinarian will give you directions on how to care for your dog. He will want to see him for follow-up visits to be sure he is recovering properly. He will also tell you what to watch for in terms of side-effects from the treatment or any new symptoms. If your dog begins to exhibit any new behaviors or symptoms, it is very important to contact your veterinarian.