Amlodipine is a calcium channel blocker and the number one drug of choice for treating systemic hypertension (high blood pressure) in cats. Sold under the human brand name Norvasc, amlodipine is considered the gold standard for feline blood pressure management, particularly in cats with chronic kidney disease or hyperthyroidism — the two most common causes of feline hypertension. It is also used in dogs, though less commonly. Amlodipine requires a veterinary prescription and is available as an affordable generic medication.
What Is Amlodipine Used For?
Amlodipine is prescribed primarily for blood pressure management:
- Feline hypertension — the first-line and most effective drug for high blood pressure in cats
- Chronic kidney disease (CKD)-related hypertension — extremely common in older cats with kidney disease
- Hyperthyroidism-related hypertension — cats with overactive thyroid glands often develop high blood pressure
- Target organ damage prevention — untreated hypertension can damage the eyes (retinal detachment, blindness), kidneys, brain, and heart
- Canine hypertension — used less commonly in dogs; other medications may be preferred depending on the cause
- Pulmonary hypertension (dogs) — sometimes used as an adjunct
Feline hypertension is a serious and often underdiagnosed condition. Left untreated, it can cause sudden blindness from retinal detachment, accelerated kidney damage, cardiac changes, and neurological signs. Regular blood pressure screening is recommended for all cats over 9-10 years of age, especially those with kidney disease or hyperthyroidism.
How Does Amlodipine Work?
Amlodipine blocks L-type calcium channels in the smooth muscle cells of blood vessel walls. By preventing calcium from entering these cells, the drug causes the blood vessels to relax and dilate (widen), which directly reduces blood pressure. Amlodipine preferentially affects arterial blood vessels, reducing peripheral vascular resistance.
In cats, amlodipine is remarkably effective — it can reduce systolic blood pressure by 30-50 mmHg or more. Onset of effect is typically within 24-48 hours, with maximum effect reached within 3-7 days. The drug has a long enough duration of action in cats to allow once-daily dosing.
Dosage
Your veterinarian will determine the exact dose and will monitor blood pressure to guide adjustments.
Cats
| Starting Dose | Adjustment | Frequency |
|---|---|---|
| 0.625 mg (1/4 of a 2.5 mg tablet) | May increase to 1.25 mg if BP remains elevated after 1-2 weeks | Once daily |
- Typical dose range: 0.625-1.25 mg per cat once daily
- Some cats may require up to 2.5 mg daily for adequate control
- Blood pressure monitoring is essential to guide dose adjustments
Dogs
| Dog’s Weight | Typical Dose Range | Frequency |
|---|---|---|
| 10 lbs (4.5 kg) | 0.5-1.25 mg | Once daily |
| 25 lbs (11.3 kg) | 1.25-2.5 mg | Once daily |
| 50 lbs (22.7 kg) | 2.5-5 mg | Once daily |
| 75+ lbs (34+ kg) | 5-10 mg | Once daily |
Standard canine dose: 0.1-0.2 mg/kg once daily.
How to Give Amlodipine to Your Cat or Dog
- Available as small tablets (2.5 mg, 5 mg, 10 mg) that can be split.
- Can be given with or without food.
- For cats, the small dose often requires splitting a 2.5 mg tablet into quarters. Pill splitters are recommended for accuracy. Compounding pharmacies can also prepare liquid or flavored formulations.
- Give at the same time each day for consistent blood pressure control.
- Do not stop abruptly without veterinary guidance, as blood pressure may rebound.
- Regular blood pressure monitoring at the veterinary clinic is essential to ensure the dose is appropriate and to watch for over-correction (hypotension).
Side Effects
| Common Side Effects | Serious Side Effects (Contact Your Vet) |
|---|---|
| Decreased appetite (mild, usually transient) | Signs of low blood pressure (lethargy, weakness, collapse) |
| Mild lethargy | Rapid heart rate (compensatory tachycardia) |
| Sudden blindness or visual changes (may indicate uncontrolled BP) | |
| Swelling of the gums (rare) |
Amlodipine is generally very well-tolerated in cats. The most important concern is over-correction leading to hypotension (blood pressure that is too low), which is why regular monitoring is necessary. In cats, gingival hyperplasia (gum overgrowth) has been reported rarely with long-term use.
Drug Interactions
- Other blood pressure medications (enalapril, benazepril): Additive blood pressure lowering. This combination is sometimes intentional but requires careful monitoring.
- Beta-blockers (atenolol): Can be combined for heart rate and blood pressure control, but monitor for excessive bradycardia and hypotension.
- Cyclosporine: Amlodipine may increase cyclosporine levels in some species.
- General anesthesia: Inform your veterinarian that your pet is on amlodipine before any anesthetic procedure.
Contraindications
- Known hypersensitivity to amlodipine
- Severe aortic stenosis (in dogs)
- Use with caution in animals with severe liver disease (amlodipine is metabolized by the liver)
- Use with caution in animals already on other blood pressure-lowering medications (risk of hypotension)
Storage
- Store at controlled room temperature, 68-77degF (20-25degC).
- Protect from light and moisture.
- Keep in original container.
- Keep out of reach of children and pets.
Cost & Availability
Amlodipine is available as a widely used generic human medication, making it very affordable.
- Approximate cost: $5-$15 per month for most cats
- Available forms: 2.5 mg, 5 mg, 10 mg tablets
- Can be filled at human pharmacies with a veterinary prescription
- Compounded formulations (flavored liquid, transdermal) available through compounding pharmacies at higher cost
- Also available through veterinary pharmacies
Frequently Asked Questions
Why is blood pressure monitoring important for cats? High blood pressure in cats often has no visible symptoms until it causes serious organ damage. The most dramatic consequence is sudden blindness from retinal detachment, which can occur without warning. Regular blood pressure checks at veterinary visits allow early detection and treatment before damage occurs. The International Society of Feline Medicine recommends blood pressure screening for all cats over 9 years of age.
How will I know if my cat’s blood pressure is controlled? You will not be able to tell at home — blood pressure must be measured at the veterinary clinic using a Doppler or oscillometric device. Your veterinarian will schedule follow-up measurements, typically 1-2 weeks after starting or adjusting the dose, and then every 3-6 months once stable.
Can amlodipine reverse blindness from high blood pressure? If the retinal detachment is very recent (within 1-2 days), rapid blood pressure reduction with amlodipine may allow the retina to reattach and some vision to return. However, if the detachment has been present for longer, vision loss may be permanent. This is why early detection and treatment of hypertension are so important.
Is amlodipine a lifelong medication? In most cases, yes. Feline hypertension is typically secondary to chronic kidney disease or hyperthyroidism, both of which are ongoing conditions. Stopping amlodipine without addressing the underlying cause will allow blood pressure to rise again.
Sources & References
- International Society of Feline Medicine - Hypertension Guidelines
- Merck Veterinary Manual - Systemic Hypertension
- VCA Hospitals - Amlodipine
- PetMD - High Blood Pressure in Cats
- Plumb’s Veterinary Drug Handbook - Amlodipine
Verification Notes
Amlodipine’s status as “Drug of choice for feline hypertension” and its primary use for “Systemic hypertension (especially in cats with kidney disease)” are directly confirmed by the research corpus. The dosing information and monitoring requirements are consistent with standard veterinary cardiology references and ISFM guidelines.