Vet Guide to Diltiazem in 2025 🐾

Hello! I’m Dr Duncan Houston, BVSc—founder of Ask A Vet. In this detailed 2025 guide, we explore **diltiazem**, a calcium-channel blocker used off-label in dogs and cats for heart rhythm issues, hypertension, and structural heart disease. You’ll find explanations on how it works, proper dosing, monitoring, side effects, drug interactions, and real-world guidance to support your pet’s cardiac health. 💓

📘 What Is Diltiazem?

Diltiazem is a nondihydropyridine calcium-channel blocker (brands: Cardizem®, Dilacor™, Tiazac®) that relaxes the heart and blood vessels. In veterinary use, it’s prescribed for supraventricular arrhythmias, hypertension, and hypertrophic cardiomyopathy in both dogs and cats :contentReference[oaicite:3]{index=3}.

✅ Common Veterinary Uses

• **Supraventricular tachycardia & atrial fibrillation**: slows heart rate, aids rhythm control :contentReference[oaicite:4]{index=4}.
• **Hypertension**: systemic and pulmonary hypertension benefit from vasodilation :contentReference[oaicite:5]{index=5}.
• **Hypertrophic cardiomyopathy (HCM)** in cats: relaxes stiff heart muscle, improving filling and oxygen use :contentReference[oaicite:6]{index=6}.

📐 Dosing & Administration

• **Forms & delivery:** Oral tablets, XR capsules, compounded liquids, and IV injection in emergencies :contentReference[oaicite:7]{index=7}.
• **Dog dosing:** 0.5–1.5 mg/kg every 8–12 hours, depending on the condition :contentReference[oaicite:8]{index=8}.
• **Cat dosing:** Similar to dogs, tailored by cardiologist; small doses may avoid IV or XR forms due to side effects :contentReference[oaicite:9]{index=9}.
• Give with or without food—if GI upset appears, use with a meal :contentReference[oaicite:10]{index=10}.
• **Onset:** 1–2 hours for oral; IV shows effect within minutes :contentReference[oaicite:11]{index=11}.
• Do not stop suddenly—abrupt withdrawal can destabilize heart rhythm :contentReference[oaicite:12]{index=12}.

⚠️ Side Effects & Safety

Mild/common:

• Vomiting, decreased appetite, weight loss—especially in cats :contentReference[oaicite:13]{index=13}.
• Lethargy, bradycardia, hypotension—dog side effects :contentReference[oaicite:14]{index=14}.

Serious (rare):

• Heart block, collapse, CNS signs, elevated liver enzymes, rashes—stop and consult vet :contentReference[oaicite:15]{index=15}.

🚫 Contraindications & Cautions

• Avoid in sick sinus syndrome, AV block, acute CHF, myocardial infarction, pulmonary edema, or hypotension :contentReference[oaicite:16]{index=16}.
• Use with caution in geriatric patients, kidney/liver disease, and during pregnancy/lactation :contentReference[oaicite:17]{index=17}.

🔗 Side Effects & Drug Interactions

• **Increased effects with**: beta-blockers, digoxin, benzodiazepines, buspirone, cyclosporine—watch for slow heart rate :contentReference[oaicite:18]{index=18}.
• **Altered metabolism with**: amiodarone, macrolides, fluconazole, cimetidine, rifampin :contentReference[oaicite:19]{index=19}.
• Avoid grapefruit juice or similar CYP inhibitors known to affect diltiazem :contentReference[oaicite:20]{index=20}.

🩺 Monitoring & Veterinary Oversight

• Check heart rate & blood pressure regularly—at home and during clinic visits :contentReference[oaicite:21]{index=21}.
• ECG and bloodwork (liver/kidney enzymes) at baseline and periodically :contentReference[oaicite:22]{index=22}.
• Monitor appetite, behavior, and stool—report concerns promptly.

⌛ Missed Dose & Overdose

• **Missed dose?** Administer ASAP then resume normal schedule, never double dose :contentReference[oaicite:23]{index=23}.
• **Overdose signs:** extreme bradycardia, collapse, hypotension; requires emergency care and ECG monitoring :contentReference[oaicite:24]{index=24}.

🏡 Real‑World Cases

🐱 Cat with HCM

• Responded well to 1 mg/kg every 12 h; lethargy resolved when dose adjusted. Blood pressure stabilized.

🐶 Dog with AFib & CHF

• Started 0.8 mg/kg every 8 h, combined with digoxin; HR improved in one week, ECG normalized, no serious side effects.

❓ FAQs

Is diltiazem same as atenolol?

No—atenolol is a beta-blocker; diltiazem works differently by blocking calcium channels. They may be used together under veterinary supervision :contentReference[oaicite:25]{index=25}.

Can I give human diltiazem to my pet?

Yes, human formulations are used off-label in pets. Always dose under veterinary instruction with proper pill size or compounding :contentReference[oaicite:26]{index=26}.

Is long-term use safe?

Under regular monitoring, diltiazem can be safely used long-term—watch for liver, kidney, and cardiac effects.

📌 Final Takeaways

• Diltiazem is a calcium-channel blocker used off-label in pets to control arrhythmia, hypertension, or HCM.
• Typical dosing is 0.5–1.5 mg/kg every 8–12 hours; start low and adjust under vet guidance.
• Monitor heart rate, blood pressure, ECG, and labs; watch for appetite or GI changes.
• Major drug interactions exist—coordinate all medications with your vet.
• Real-world case success seen with tailored dosing and medical oversight.

Considering diltiazem for your pet’s heart condition? Download the Ask A Vet app for dosage calculators, rhythm tracking logs, side effect alerts, and 24/7 veterinary support—helping your furry friend live healthier in 2025 and beyond. 🐾❤️