Prescription pillsWhat is Diltiazem?

Diltiazem is in the family of medications known as calcium channel blockers. It blocks the movement of calcium into muscle cells resulting in relaxation of heart muscle, dilation of arteries, and slowing of the electrical impulses through the heart. It is used in dogs and cats for the treatment of certain cardiac diseases and arrhythmias.


  • Hypertrophic Cardiomyopathy
  • Heart rate control in patients with Atrial Fibrillation
  • Supraventricular Arrhythmias
  • Rarely used to treat systemic and pulmonary hypertension

Adverse Effects 

[please contact CVCA should any of these symptoms be noted]

  • Vomiting and decreased appetite are the most common side effects
  • Due to its bitter taste it can cause excessive salivation and food aversion
  • Low blood pressure, weakness, lethargy and slow heart rates
  • Rarely elevation in liver function tests or worsening constipation can also occur

Client Information

  • Can be given with food and other cardiac medications as outlined by CVCA
  • Given in pill form or reformulated into a flavored liquid
  • Given 1 to 3 times daily depending on drug formulation and/or disease being treated
  • Close monitoring of the blood pressure and heart rate while on this medication is recommended
  • Do not abruptly stop or reduce therapy without veterinarian’s approval
  • Contact a veterinarian about the dosage if anesthesia is required

Interactions with Other Drugs

  • Increased risk of low heart rate and low blood pressure when used in combination with beta blockers (atenolol), amlodipine, acepromazine, ACEi (enalapril, benazepril)
  • Increases the strength of certain drugs (benzodiazepines like valium/alprazolam, and cyclosporine)
  • The doctors at CVCA have taken this into account, however, please feel free to contact us regarding any concurrent medications your pet may be prescribed

Dosage Forms

Diltiazem Tablets – 30mg, 60mg, 90mg, and 120mg

Diltiazem Extended Release Oral Capsules – 120, 180 and 240mg (May need to open the capsule and remove the four individual tablets and administer 1 or more of the tablets)

Cardizem CD Capsules – 120mg, 180mg, 240mg and 300mg (these capsules should be swallowed whole and not chewed)


(Diltiazem, Cardizem, Cardizem CD, Dilacor XR)

Drug Handouts