Calcium Channel Blockers Poisoning in Dogs

Calcium channel blockers are used to treat hypertension and heart disease. These medications aid in relaxing the blood vessels while increasing the supply of oxygen and blood to the heart. This is accomplished while also decreasing the workload of the heart. While treating high blood pressure, calcium channel blockers also are quite effective at treating angina, diastolic heart failure, cardiac arrhythmia, and coronary artery disease.

Calcium channel blockers work by reducing the amount of calcium that is passed into the cells of the muscles of the heart. This type of medication causes the muscles of the heart to remain relaxed when contracting. Calcium channel blockers are quite effective at widening the arteries which help reduce blood pressure. When dogs ingest calcium channel blockers they can become poisoned quite rapidly. Calcium channel blockers are absorbed rapidly from the gastrointestinal tract, in the dog can show signs of poisoning within 20 to 45 minutes. This also depends on the amount ingested. 

Calcium channel blockers poisoning in dogs occurs when dogs ingest this type of heart medication, usually given to humans for a variety of heart disorders.

Symptoms occur quite rapidly when a dog has consumed calcium channel blockers. Symptoms can include:

• Nausea
• Vomiting
• Slow heart rate (bradycardia)
• Lethargy
• Weakness
• Collapse

Types

Calcium channel blockers can have a variety of names. If your dog has ingested any medication, do not hesitate to take the bottle to the veterinarian. Alternate names for this type of medication include:

• Verapamil
• Amlodipine 
• Nifedipine
• Nimodipine
• Nicardipine
• Nisoldipine
• Felodipine
• Isradipine
• Clevidipine
• Generic heart medication
• Generic cardiac medication

The cause of calcium channel blocker poisoning occurs when a dog overdoses on this type of heart medication, even in very small amounts. Causes of calcium channel blocker poisoning specifically occur as a result of:

• Causing abnormal potassium levels
• Electrolyte disturbances
• Pulmonary edema

If your dog has ingested calcium channel blockers, it is important to seek medical treatment immediately. Once you have taken your dog to the veterinarian, he will begin a complete physical examination, including blood work, urinalysis, and biochemistry profile. The veterinarian will check the level of electrolytes and the blood potassium level.

By looking at the symptoms and by knowing if the dog has possibly or definitely ingested calcium channel blockers, he will begin to perform an electrocardiogram. The electrocardiogram will show the veterinarian if the dog has any junctional rhythms, a very slow heart rate (bradycardia), or an atrioventricular block.

The veterinarian will be able to come up with a definitive diagnosis of calcium channel blocker toxicity by relying on the dog’s clinical signs, his knowledge of the history of ingestion of the medication, and the electrocardiogram. These alone will help the veterinarian be able to begin treatment very quickly.

Treatment of calcium channel blockers must start immediately in order for it to be successful. Treatment methods include:

Decontamination

Gastric lavage or emesis may be given if large amounts were ingested. Activated charcoal, in addition to a cathartic, will absorb and further increase the excretion of any remaining poison. Decontamination may only occur if the dog is stable, as it is very important to protect the airway. Activated charcoal may  be given every 4 to 6 hours and may be repeated as the veterinarian deems necessary.

Monitoring

The veterinarian will monitor the dog’s cardiovascular functionality with electrocardiograms, and by measuring the blood pressure and repeated checking of the blood glucose levels in the concentrations of serum electrolytes.

Medications

There are several medications that can be given to help a dog that is suffering from toxicity. Intravenous lipid emulsions, calcium, atropine, vasopressin, glucagon, and vasopressin are options in treatment with medication. The veterinarian will make the decision on which medications would be more effective in treating your dog.

Intravenous calcium

Calcium is highly effective in treating channel blocker toxicity, as it increases the concentration of calcium within the cells. This, in turn, stimulates the sarcoplasmic reticulum and encourages it to release a greater quantity of calcium into the dog’s cytoplasm. Calcium may help with stabilizing and increasing blood pressure, inotropy, and cardiac output.

If your dog received immediate medical treatment for an overdose of calcium channel blockers, the prognosis is fair to good. This depends on the amount of medication ingested and how much time had passed before treatment. The veterinarian will want to continuously monitor your dog once he is stabilized. When you are able to take him home, the veterinarian will guide you in the monitoring care of your dog. He will also want to see him for follow-up visits to be sure he is continuing to recover.

If your dog is on medications prescribed by the veterinarian, it will be very important for you to administer them properly carefully. If you see any side-effects from any medication, or if any new symptoms occur with or without any medication, it will be very important for you to contact your veterinarian.