# Amlodipine Side Effects in Cats: What to Expect Most cats handle amlodipine well, and the side effects owners notice most often are mild and temporary. The bigger danger is usually the high blood pressure itself, which can damage the eyes, brain, kidneys, and heart if it goes untreated [1]. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Amlodipine is a calcium channel blocker, and it is the antihypertensive drug used most often in cats with high blood pressure [1]. - Common, usually mild effects include sleepiness, wobbliness, and a drop in appetite during the first days of treatment. - The most serious concern is low blood pressure (hypotension), which can cause weakness, collapse, or fainting. - Blindness in a hypertensive cat is usually caused by the high blood pressure damaging the retina, not by amlodipine, so the drug is often part of the effort to protect vision. - Never change the dose on your own. Your veterinarian sets the dose from your cat's weight, blood pressure, and other health problems. ## What Amlodipine Is and Why Veterinarians Prescribe It Amlodipine besylate is an oral medication that belongs to a class called calcium channel blockers. In cats, it is used mainly to treat systemic hypertension, which means high blood pressure throughout the body. A survey of hypertensive cats in Japan found that amlodipine was used in every cat treated for high blood pressure, either alone or with other drugs [1]. High blood pressure in cats is often called the "silent killer" because owners rarely see signs until an organ is damaged. The brain, eyes, kidneys, and cardiovascular system are the main target organs [1]. Many hypertensive cats also have chronic kidney disease, and the two conditions often travel together. Amlodipine is sometimes prescribed for cats with certain heart conditions as part of a broader treatment plan. One report described a cat with a ventricular septal defect who received amlodipine along with pimobendan, furosemide, and clopidogrel before surgical repair [2]. That is a specialized situation, and it does not mean amlodipine treats all heart disease. ## How Amlodipine Works in a Cat's Body Amlodipine relaxes the smooth muscle in the walls of arteries. When those vessels widen, blood pressure falls. This is why the drug is so effective for the kind of hypertension cats get, which is driven largely by tightened peripheral arteries. The drug also interacts with the renin-angiotensin-aldosterone system (RAAS), the hormone network that controls blood pressure and fluid balance. In healthy cats given amlodipine, markers of plasma renin concentration rose by a median of about 44% compared with placebo [3]. In hypertensive cats with chronic kidney disease who were taking amlodipine, several RAAS components (angiotensin 1, angiotensin 1,7, angiotensin III, angiotensin 1,5, and ACE-2 activity) were higher than in normotensive cats, while ACE activity was lower [4]. Aldosterone was also significantly higher in the treated hypertensive group [4]. What does that mean for you? It means amlodipine lowers blood pressure effectively, and the body's hormone systems respond to that change. It is one reason your veterinarian may want to monitor kidney values and electrolytes over time, and it is why some cats need more than one medication. ## Dosing Basics: Who Decides and How to Give It Your veterinarian decides the dose. There is no universal number that fits every cat. The dose depends on your cat's weight, measured blood pressure, kidney function, and other medications. If you want to understand how dosing and monitoring fit together, this guide on [amlodipine cat hypertension dose and blood pressure monitoring](/knowledge/veterinary-medicine/calculators-clinical-tools/amlodipine-cat-hypertension-dose-blood-pressure-monitoring-guide) walks through the process. Amlodipine is given by mouth, usually once daily. It can be given with or without food. Many cats take it in a small treat, a pill pocket, or a compounded liquid if your veterinarian arranges that. Try to give it at the same time each day so blood pressure stays steady. If you miss a dose, do not double up. Give the next dose at the normal time and call your veterinarian if you are unsure. If you miss several doses, call before restarting, because blood pressure can climb again. Never split, crush, or change the dose unless your veterinarian tells you to. Some cats are started at a low dose and rechecked, then adjusted. Blood pressure rechecks are how your veterinarian knows the drug is working. ## Amlodipine for Cats Side Effects: What to Expect Most side effects are mild and show up in the first days of treatment or after a dose increase. Your cat's body is adjusting to lower blood pressure, and that adjustment can feel strange at first. | Side effect | How common or serious | What to do | |---|---|---| | Sleepiness or low energy | Common and usually mild | Give the drug as directed and watch for improvement over a few days. Call if it lasts or worsens. | | Wobbliness or unsteady walking | Fairly common early on | Keep your cat indoors and away from stairs. Call your veterinarian if it does not settle. | | Reduced appetite | Common early | Offer favorite foods. Call if your cat stops eating for more than a day. | | Vomiting or drooling | Uncommon | Call your veterinarian if it repeats or your cat cannot keep the pill down. | | Weakness, collapse, or fainting | Uncommon but serious | This can mean low blood pressure. Treat it as an emergency. | | Gums that look pale or gray | Serious | Emergency. Go to a veterinarian now. | | Swelling of the paws or limbs | Uncommon | Call your veterinarian. This can be a sign of fluid shifting. | | Kidney values that worsen | Possible over time | Detected on bloodwork, not at home. Keep monitoring appointments. | Two things are worth separating here. First, sleepiness and wobbliness often fade as your cat adapts. Second, true hypotension is different. It looks like profound weakness, a cat who will not stand, cold limbs, or collapse. That is not a wait-and-see situation. If your cat takes other medications for allergies, seizures, or pain, the same rule applies: watch for changes after any new drug starts. These guides on [Apoquel side effects in cats](/knowledge/veterinary-medicine/pet-medication-guide/apoquel-side-effects-cats), [seizure medication side effects in cats](/knowledge/veterinary-medicine/pet-medication-guide/seizure-medication-side-effects-cats), and [gabapentin side effects in cats](/knowledge/veterinary-medicine/pet-medication-guide/gabapentin-side-effects-cats) cover that ground. ### Amlodipine for Cats and Blindness: What Owners Need to Know This is the question that worries owners most, so let's be clear. Blindness in a hypertensive cat is caused by the high blood pressure, not by amlodipine. Sustained high pressure damages the small vessels in the retina, and the retina can detach. That damage can happen fast, sometimes within days. Amlodipine is given to lower that pressure and protect the eyes, brain, kidneys, and heart [1]. In other words, the drug is part of the defense against blindness, not the cause of it. If your cat is already blind when treatment starts, vision may or may not return. Some cats regain some sight, and some do not. Your veterinarian can assess the retina and give you a realistic picture. If your cat suddenly bumps into things, holds the head oddly, or has pupils that stay wide in bright light, that is an emergency. Call your veterinarian or an emergency clinic right away. ### Blood Pressure That Drops Too Low Amlodipine works by lowering blood pressure, so it can overshoot. This is more likely if the dose is too high, if your cat is dehydrated, or if other blood pressure drugs are on board. Signs of low blood pressure include extreme lethargy, reluctance to move, wobbling that does not improve, collapse, and pale gums. If you see these, stop giving the medication and contact a veterinarian immediately. Do not wait for the next scheduled recheck. One interesting finding from a Japanese survey: cats whose systolic pressure was pushed down into the normal range (below 140 mmHg) may have had a negative impact on survival compared with cats whose pressure stayed a bit higher [1]. That does not mean you should aim for high blood pressure. It means the target range is a clinical judgment, and your veterinarian will weigh the risks for your individual cat. ## Who Should Not Take Amlodipine and What Interacts With It Amlodipine is not right for every cat. Your veterinarian will consider the whole picture before prescribing it. Cats who should be evaluated carefully or may not be good candidates include: - Cats with very low blood pressure or shock - Cats who are severely dehydrated - Cats with certain heart conditions where vasodilation could be harmful - Cats with liver disease, since the liver processes the drug - Pregnant or nursing cats, because safety is not well established in veterinary research Drug interactions matter too. Amlodipine can add to the blood pressure-lowering effect of other antihypertensives, which raises the risk of hypotension. It is often combined with RAAS-suppressing drugs in cats with kidney disease, and that combination needs monitoring [4]. Tell your veterinarian about every medication, supplement, and topical product your cat receives, including flea and tick products. Because amlodipine affects the RAAS, cats on it may show changes in hormone markers and kidney values over time [3][4]. That is expected, and it is why follow-up bloodwork matters. ## Overdose: What to Do Right Now If your cat gets too much amlodipine, act fast. Signs of overdose include severe weakness, collapse, fainting, cold limbs, pale gums, vomiting, and a very slow or very fast heart rate. Call your veterinarian or an emergency clinic immediately. In the United States, you can also call the ASPCA Animal Poison Control Center at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661. Have the pill strength, the number of pills your cat may have eaten, your cat's weight, and the time it happened ready. Do not try to make your cat vomit unless a veterinarian tells you to. Do not wait to see if symptoms appear. Low blood pressure from an overdose can worsen quickly. ## Limitations and When to Contact a Veterinarian No article can tell you what is happening inside your specific cat. Blood pressure, kidney values, and retinal exams are how your veterinarian tracks treatment. Individual cases need a veterinarian. Contact your veterinarian the same day if your cat: - Refuses food for more than 24 hours - Vomits repeatedly or cannot keep the medication down - Seems more tired than usual for more than a few days - Develops wobbliness that does not improve - Has swelling in the limbs or face Go to an emergency clinic now if your cat: - Collapses or faints - Cannot stand or walk - Has pale, gray, or blue gums - Breathes rapidly or with effort - Suddenly seems blind, bumps into furniture, or has wide pupils that do not react to light - Has a seizure Keep routine rechecks on schedule. Blood pressure checks, bloodwork, and eye exams catch problems before you see them at home. If cost is a concern, ask your veterinarian which tests are most important at each visit. ## Frequently Asked Questions ### How long do amlodipine side effects last in cats? Most mild effects, such as sleepiness and wobbliness, ease within a few days as your cat adjusts to lower blood pressure. If they last longer or get worse, call your veterinarian. A dose adjustment may be needed. ### Can amlodipine cause blindness in cats? No. Blindness in hypertensive cats comes from the high blood pressure damaging the retina, and amlodipine is given to lower that pressure and protect the eyes [1]. Sudden vision loss is still an emergency, so call your veterinarian right away if it happens. ### What should I do if my cat seems weak after taking amlodipine? Stop the medication and call your veterinarian or an emergency clinic immediately. Weakness, collapse, or fainting can signal low blood pressure. Do not give another dose until a veterinarian tells you to. ### Can I give amlodipine with my cat's other medications? Sometimes, but it depends on the drugs. Amlodipine is often combined with other medications in cats with kidney disease, and that combination needs monitoring [4]. Always tell your veterinarian about every product your cat takes before mixing anything. ### Does my cat need blood tests while on amlodipine? Yes, periodic bloodwork is typical. Amlodipine affects the renin-angiotensin-aldosterone system, and treated cats can show changes in those markers and in kidney values over time [3][4]. Your veterinarian will set the schedule based on your cat's health. ## Related Articles - [What Are the Side Effects of Apoquel for Cats?](/knowledge/veterinary-medicine/pet-medication-guide/apoquel-side-effects-cats) - [What Are the Side Effects of Seizure Medication in Cats?](/knowledge/veterinary-medicine/pet-medication-guide/seizure-medication-side-effects-cats) - [Cat Allergy Medication Side Effects: What to Watch For](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-allergy-medication-side-effects) - [What Are the Side Effects of Gabapentin for Cats?](/knowledge/veterinary-medicine/pet-medication-guide/gabapentin-side-effects-cats) - [Amlodipine Cat Hypertension Dose: Blood Pressure Monitoring Guide](/knowledge/veterinary-medicine/calculators-clinical-tools/amlodipine-cat-hypertension-dose-blood-pressure-monitoring-guide) - [Cat Anxiety Medication: What You Need to Know](/knowledge/veterinary-medicine/anxiety-and-behavior-support/cat-anxiety-medication) - [Amlodipine for Dogs and Cats: Uses and Safety](/knowledge/veterinary-medicine/pet-medication-guide/amlodipine-dogs-cats) - [Missed Amlodipine Dose in Cats: What to Do Next](/knowledge/veterinary-medicine/pet-medication-guide/amlodipine-missed-dose-cats) - [Amlodipine for Cats With Kidney Disease: Safe Use](/knowledge/veterinary-medicine/senior-and-chronic-care/amlodipine-cats-kidney-disease) ## References 1. [Use of amlodipine in the treatment of cats with systemic hypertension in Japan](https://pubmed.ncbi.nlm.nih.gov/38569838/). The Journal of veterinary medical science, 2024. 2. [Surgical correction of ventricular septal defect in a cat](https://pubmed.ncbi.nlm.nih.gov/40334632/). Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology, 2025. 3. [Effect of amlodipine on the circulating renin-angiotensin-aldosterone system in healthy cats](https://pubmed.ncbi.nlm.nih.gov/38334012/). Journal of veterinary internal medicine, 2024. 4. [Evaluation of Renin-Angiotensin-Aldosterone System Components and Enzymes in Systemically Hypertensive Cats Receiving Amlodipine](https://pubmed.ncbi.nlm.nih.gov/38003097/). Animals : an open access journal from MDPI, 2023. ## Further Reading - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners) - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information)