Amlodipine for Cats in 2025: Vet‑Approved Hypertension Treatment Guide 🐱💊🫀

By Dr Duncan Houston, BVSc
Updated July 2025

💡 Amlodipine besylate (brand names: Norvasc®, Istin®) is a calcium channel blocker increasingly used to manage hypertension in cats—and occasionally dogs. This 2025 guide explains how it works, when to use it, how to give it, what to watch for, and how to safely monitor your pet’s blood pressure.

🔬 How It Works

Amlodipine blocks calcium entry into arterial muscle cells, causing vessels to relax and dilate. This lowers systemic blood pressure without significantly weakening the heart’s pumping strength, making it ideal for treating feline hypertension.

📌 When to Use

• Systolic blood pressure ≥160 mmHg, especially if associated with kidney disease, hyperthyroidism, cardiomyopathy, or retinal changes
• Higher risk when BP ≥180 mmHg due to organ damage concerns

⏳ Administration & Timing

• Available in 2.5 mg, 5 mg, and 10 mg tablets
• Given once daily—can be with or without food
• Onset of action: 4–6 hours in cats and dogs
• If a dose is missed, give when remembered—never double the next dose
• Store at room temperature, protected from light
• Performs best when tablet pieces are accurately sized—consider pill cutters or compounding pharmacies for accurate dosing

⚠️ Common Side Effects

• In cats: rare reports of elevated kidney values, low potassium, lethargy, increased heart rate, and weight loss—monitor these closely
• In dogs: gingival gum overgrowth affects ~8.5% of treated pets
• Human-reported side effect of headaches likely goes undetected in pets

⚖️ Monitoring Expectations

• Recheck blood pressure 1–2 weeks after starting and periodically thereafter
• Conduct annual or biannual bloodwork—evaluate kidney, liver, and electrolyte status
• Watch for lethargy, appetite changes, or weakness—could indicate overtreatment (hypotension)
• Have ophthalmic exams to monitor for hypertension-related retinal damage

🔄 Drug Interactions

• May cause excessive blood pressure drops if combined with diuretics, ACE inhibitors, beta-blockers, or fentanyl
• Elevates cyclosporine levels—monitor accordingly
• Amlodipine levels may increase when taken with ketoconazole or itraconazole
• May reduce the effectiveness of clopidogrel (blood thinner)

🚨 Special Precautions

• Adjust dosage for pets with liver disease—slower metabolism increases effect
• Use cautiously in animals with existing heart failure
• Avoid use in pregnant pets due to safety concerns
• Encourage owners to give doses consistently and monitor for missed doses—abrupt discontinuation can elevate blood pressure rapidly

📱 Ask A Vet App Integration

Need help managing feline hypertension, tracking blood pressure trends, or adjusting dosing? The Ask A Vet app offers:

• 📊 Personalized monitoring plans and reminder tools
• ⚕️ Access to veterinary advice for dosage adjustments
• 🩺 Support in detecting early signs of hypotension or interaction concerns

➡️ Download the app today to work closely with your vet on your cat’s cardiovascular care. Visit AskAVet.com.

✅ Final Takeaways from Dr Duncan Houston

• Amlodipine is now the most commonly prescribed antihypertensive in cats—and a useful option in dogs with hypertension
• Once-daily dosing and minimal cardiac impact enhance compliance and safety
• Side effects are typically mild but monitoring blood pressure and kidney function is critical
• Drug interactions and liver impairment should guide care decisions

🫀💊 With thoughtful use, amlodipine can greatly improve quality of life for hypertensive cats in 2025—supporting ongoing health with measurable monitoring and professional oversight.