Diltiazem HCl (Cardizem®, Dilacor XR®) for Cats and Dogs

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Overview of Diltiazem HCl for Cats and Dogs

  •  Diltiazem, commonly known by the brand name Cardizem® and Dilacor XR®, is used in dogs and cats to treat cardiac arrhythmias, hypertension (high blood pressure) and for the management of heart disease.
  • Diltiazem is categorized as a calcium channel blocker drug. Calcium is an important mineral in the function of the heart. Calcium enters the heart muscle cells through calcium channels, which are pores located in the cell membrane.
  • Calcium ions prompt the heart muscle to contract, stimulate the natural pacemaker of the heart and influence conduction of current across heart cells.
  • Calcium channels also are found in blood vessels. These channels allow calcium ions to enter the cell. The result is constriction (narrowing) of the vessel.
  • Calcium channels are carefully regulated by the nervous system and by a number of hormones.
  • Diltiazem HCl belongs to a general class of drugs known as calcium channel blockers. Other related drugs in this class include verapamil (Calan®, Isoptin®), nifedipine (Procardia®) and amlodipine (Norvasc®).
  • Diltiazem inhibits the entry of calcium into heart muscle cells by partially blocking some of the calcium channels. This reduces the strength of contraction in heart muscle cells.
  • In blood vessels, calcium channel blockers prevent calcium entry, leading to widening of the arteries, which lowers blood pressure and reduces the resistance to ejection of blood from the heart.
  • Diltiazem also affects electrical activity in the heart. The effects are slowing of the heart beat and delayed electrical conduction across the tissues between the upper chambers (atria) and lower chambers (ventricle).
  • Diltiazem is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
  • This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.
  • Brand Names and Other Names of Diltiazem HCl

  • This drug is registered for use in humans only.
  • Human formulations: Cardizem® (Hoechst Marion Roussel), Tiamate®, Dilacor XR® (Rhone-Poulenc Rorer) and Tiazac® (Forest)
  • Veterinary formulations: None

    Uses of Diltiazem for Dogs and Cats

  • The primary use of diltiazem is for treatment (and sometimes prevention) of cardiac arrhythmias, including atrial fibrillation, atrial flutter and supraventricular tachycardia.
  • Diltiazem is also used in management of some cats with the heart muscle disease hypertrophic cardiomyopathy.
  • Diltiazem can lower high blood pressure; however, other calcium channel blockers are more effective for this purpose.
  • Precautions and Side Effects

  • While generally safe and effective when prescribed by a veterinarian, diltiazem can cause side effects in some animals.
  • Diltiazem should not be used in animals with known hypersensitivity or allergy to the drug.
  • Diltiazem may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with diltiazem. Such drugs include digoxin, propranolol, cimetidine and cyclosporin.
  • Diltiazem may relax blood vessels or depress the heart contraction or rate to such a degree that some animals become weak due to low blood pressure.
  • Side effects include vomiting, diarrhea, loss of appetite and a slow heart rate. Any symptoms should be reported to your veterinarian.
  • Diltiazem must be given with care to animals with heart failure. High doses can depress heart muscle function.
  • Side effects are more likely when diltiazem is administered with other potent cardiovascular drugs, such as diuretics or other vasodilators (drugs that act to relax blood vessels).
  • How Diltiazem Hydrochloride Is Supplied

  • Diltiazem is available in 30 mg, 60 mg, 90 mg and 120 mg tablets.
  • Diltiazem extended-release tablets is supplied as 120 mg, 180 mg and 240 mg tablets.
  • Diltiazem extended-release capsules are supplied as 60 mg, 90 mg, 120 mg, 180 mg, 240 mg, 300 mg and 360 mg capsules.
  • Diltiazem injectable is supplied as 5 mg/ml.
  • Dosing Information of Diltiazem HCl for Dogs and Cats 

  • Medication should never be administered without first consulting your veterinarian.
  • Dilacor® or Cardizem CD® (long-acting forms of diltiazem) may be recommended for the convenience of once-daily dosing in cats and twice-daily dosing in dogs. 
  • The typical dose of diltiazem administered to dogs is 0.25 to 0.5 mg per pound (0.5 to 1.0 mg/kg) every eight hours, but the dose is quite variable depending on the response and underlying medical condition. When a sustained-release product is used in dogs, 1.5 to 2.5 mg per pound (3 to 5 mg/kg) orally twice daily is recommended. The dose can vary greatly depending on the underlying heart disease and your dogs response to treatment. 
  • The typical dose administered to cats is 7.5 mg to 15 mg per cat two to three times daily. When a sustained-release product is used in cats, 30 to 45 mg per cat orally once daily is recommended. 
  • An injectable version is available for emergency treatment of supraventricular arrhythmias. 
  • Frequently diltiazem is given with other drugs, especially in pets undergoing treatment for heart failure or arrhythmias (abnormal heart rhythm). In these situations, a lower initial dose may be prescribed to allow the pet time to adjust to the new medication.
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse.
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