Amlodipine and Mirtazapine in Kidney Disease
By Dr. Zubair Khalid, DVM, MS, PhD ·
Chronic kidney disease often brings two problems at once: high blood pressure and poor appetite. Amlodipine for dogs with kidney disease (and cats) lowers blood pressure, while mirtazapine helps pets eat again. Many pets need both drugs at the same time, and understanding why can make daily care much easier.
This article is educational and is not a substitute for veterinary diagnosis or treatment.
Quick Answer
- Amlodipine is a blood pressure medicine. It relaxes blood vessels so the heart does not have to push as hard, which protects the kidneys, eyes, brain, and heart from damage caused by hypertension [1].
- Mirtazapine is an appetite stimulant and anti-nausea drug. It is used widely in cats and has growing evidence for use in dogs with poor appetite [2][3].
- These drugs treat different problems, so they are often prescribed together in pets with kidney disease. One controls blood pressure, the other supports nutrition.
- Your veterinarian sets every dose based on your pet's weight, kidney values, blood pressure readings, and other medications.
- Never start, stop, or change either drug on your own. Both can cause real problems if used the wrong way.
What These Medicines Are and What Veterinarians Use Them For
Amlodipine
Amlodipine besylate is a calcium channel blocker. In veterinary medicine it is used mainly to treat systemic hypertension, which means high blood pressure throughout the body [4][1]. In cats, amlodipine is the first-choice drug for high blood pressure and is used alone or with other drugs in nearly every treated case [1].
High blood pressure damages what veterinarians call target organs: the brain, eyes, kidneys, and cardiovascular system [1]. In a pet with kidney disease, this damage makes the kidneys worse, which raises blood pressure further. Breaking that cycle is the whole point of treatment.
Mirtazapine
Mirtazapine is an orexigenic drug, meaning it stimulates appetite [2]. It is also used as an antiemetic, which means it helps control nausea and vomiting [3]. In cats it is widely prescribed for anorexia, the medical term for not eating [2][5].
In dogs, the evidence is newer but promising. A 2025 study found that dogs given mirtazapine were significantly more likely to start eating on their own again, and they lost less weight than dogs that were not treated [2]. In a controlled trial within that same study, mirtazapine increased food acceptance on the first day in 100% of treated dogs compared with 63.6% of controls [2].
Mirtazapine is also used in dogs for some behavior problems, where it has shown benefit with mild, tolerable side effects [6]. That is a different use from appetite stimulation, but it tells you the drug is generally well tolerated in dogs.
If you want more detail on the appetite-stimulant side of this drug, see mirtazapine for dogs.
How These Drugs Work
How amlodipine lowers blood pressure
Amlodipine blocks calcium channels in the smooth muscle of blood vessel walls. The vessels relax and widen, so blood flows through more easily and pressure drops. This is a mechanical, plumbing-style effect. It does not depend on the kidneys to work.
That matters because amlodipine still lowers blood pressure in pets whose kidneys are failing. A 2024 study in healthy cats found that amlodipine treatment increased plasma renin concentration by a median of 44% compared with placebo [4]. Renin is a hormone the body releases when it senses lower blood pressure. In plain terms, the drug works, and the body responds by turning up its own blood pressure hormones. This is one reason your veterinarian may combine amlodipine with other drugs and why monitoring matters.
How mirtazapine stimulates appetite
Mirtazapine works on brain chemicals that control appetite, nausea, and mood. It blocks certain serotonin and histamine receptors, which tends to make pets hungry and less queasy. In cats receiving chemotherapy, mirtazapine treatment produced significantly higher appetite and activity scores and significantly greater body weight compared with placebo [3].
In dogs, the effect appears quickly. In one trial, the average time from giving the drug to feeding was about 120 minutes [2]. The appetite boost was strong on day one but was not maintained on day two in that same trial, possibly because of how the drug behaves in the body or because the dogs were already improving [2].
Why kidney disease often needs both
Kidney disease and high blood pressure feed each other. Damaged kidneys handle sodium and fluid poorly, and hormone systems tighten blood vessels. The result is higher pressure that injures the remaining kidney tissue.
At the same time, many pets with kidney disease feel nauseated and simply stop eating. Poor nutrition speeds up muscle loss and worsens how the pet feels. So veterinarians treat the pressure with one drug and the appetite with another. The two jobs are separate, and both matter.
Diet is part of this picture too. A kidney-friendly diet can slow progression and improve how your pet feels. See Dog Kidney Disease Diet for practical guidance. For staging and long-term planning, see Canine Chronic Kidney Disease: Staging and Therapeutic Plan.
Dosing Basics
Who decides the dose
Your veterinarian does. Doses depend on your pet's weight, species, kidney values, blood pressure, other drugs, and how your pet responded to past treatments. Never use a dose you found online or one that worked for a different pet.
How the drugs are given
Both amlodipine and mirtazapine are given by mouth. Amlodipine is typically given once daily for blood pressure control [4]. Mirtazapine dosing schedules vary. In one cat study, mirtazapine was given every 48 hours [3]. In dogs, schedules are set case by case [2].
Mirtazapine has a practical problem: it tastes extremely bitter, which makes some pets refuse it [5]. Researchers have worked on taste-masked and controlled-release versions to solve this, but those products are not standard in most clinics yet [5]. If your pet fights the pill, ask your veterinarian about compounding options.
What to do about a missed dose
Call your veterinary clinic and ask. In general, do not double up to make up for a missed dose, especially with a blood pressure drug. A double dose of amlodipine can drop blood pressure too low and make your pet weak or wobbly. Write down the time of the missed dose so the clinic can advise you accurately.
If your pet vomits shortly after a dose, do not assume the drug was absorbed. Call the clinic before giving another dose.
For dose ranges and how veterinarians calculate them, see Mirtazapine Appetite Stimulant: Dose for Cats and Dogs Guide.
Side Effects
| Side effect | How common or serious | What to do |
|---|---|---|
| Low blood pressure (weakness, wobbliness, collapse) from amlodipine | Uncommon but serious | Stop the drug and call your veterinarian right away |
| Sleepiness or sedation from mirtazapine | Common, usually mild | Note the timing and mention it at the next visit |
| Increased appetite, meowing or begging for food | Expected effect, not a problem | Enjoy it, and follow your feeding plan |
| Vomiting or diarrhea | Possible with either drug | Call the clinic if it lasts more than a day |
| Vocalization or restlessness in cats | Reported with mirtazapine | Tell your veterinarian, the dose may need adjusting |
| Sudden blindness, seizures, or severe disorientation | Emergency, suggests organ damage from high blood pressure | Go to an emergency clinic now |
In the dog appetite study, no adverse effects were observed in the controlled trial portion [2]. In cats on chemotherapy, mirtazapine was well tolerated and improved weight and appetite scores [3]. In dogs treated for behavior problems, suspected adverse effects were mild and tolerable [6].
That said, individual pets react differently. Report anything new, even if it seems small.
Who Should Not Take These Drugs and What Interacts With Them
Amlodipine cautions
Amlodipine lowers blood pressure, so it should be used carefully in pets that are already hypotensive, dehydrated, or in shock. Pets with certain heart conditions may need a different plan. Your veterinarian will check blood pressure and often bloodwork before starting and during treatment.
One finding deserves attention. A study of hypertensive cats in Japan suggested that pushing systolic blood pressure below 140 mmHg with amlodipine may have a negative impact on survival [1]. That does not mean the drug is unsafe. It means the target matters, and aggressive lowering is not always better. Your veterinarian will set a goal range for your pet.
Mirtazapine cautions
Mirtazapine affects serotonin and histamine systems, so it can interact with other drugs that do the same. Tell your veterinarian about every medication, supplement, and topical product your pet receives. Pets with liver disease may clear the drug more slowly.
Because mirtazapine increases appetite, it can mask a worsening underlying problem. If your pet eats well but still loses weight or seems unwell, that is worth a call.
Kidney disease drugs in general
Many pets with kidney disease take several drugs. Angiotensin-converting enzyme (ACE) inhibitors are commonly used because they reduce protein loss in the urine and slow the harmful hormone-driven changes in the kidney [7]. In chronic kidney disease, angiotensin II drives glomerular hyperperfusion and hypertension, which initially helps filtration but causes long-term nephron loss [7]. It also raises transforming growth factor-beta, a fibrogenic cytokine that promotes scar tissue in the kidney [7].
Combining drugs that affect blood pressure and kidney hormones requires monitoring. Your veterinarian will recheck blood pressure, kidney values, and urine protein on a schedule.
Overdose and When to Call for Help
An overdose of amlodipine can cause dangerously low blood pressure. Signs include extreme weakness, collapse, pale gums, a very slow or very fast heart rate, and unresponsiveness. This is an emergency.
An overdose of mirtazapine can cause heavy sedation, agitation, vomiting, or a fast heart rate. Effects vary by species and dose.
If you suspect an overdose, call your veterinarian or an animal poison control service immediately. Have the pill bottle, the strength, and your best estimate of how many pills were taken. Do not wait for symptoms to appear.
Limitations and When to Contact a Veterinarian
This article gives general information. Your pet's case needs a veterinarian who can examine your pet, measure blood pressure, and review bloodwork.
Call the same day if your pet:
- Refuses food for more than 24 hours despite mirtazapine
- Vomits repeatedly or has diarrhea that will not stop
- Seems weak, wobbly, or unusually quiet after an amlodipine dose
- Has a missed dose and you are unsure what to do
Go to an emergency clinic now if your pet:
- Collapses or cannot stand
- Has a seizure
- Suddenly seems blind or bumps into furniture
- Breathes rapidly at rest or has pale or blue gums
- Is unresponsive or very difficult to wake
Schedule a routine visit if your pet:
- Is eating but still losing weight
- Has blood pressure readings that vary between visits
- Needs a refill and has not had bloodwork in several months
Frequently Asked Questions
Can I give amlodipine and mirtazapine at the same time?
Usually yes, and many pets take both daily. Your veterinarian will confirm the timing and whether either drug should be given with food. Do not change the schedule without asking first.
How long does mirtazapine take to work in dogs?
The appetite effect can appear within about two hours of a dose [2]. In one trial, the strongest effect was on the first day and was not maintained on the second day [2]. If your dog stops eating again, call your veterinarian.
Does amlodipine cure kidney disease?
No. Amlodipine controls blood pressure, which protects target organs from further damage [1]. It does not reverse existing kidney damage. It works best as part of a full plan that includes diet, monitoring, and other medications as needed.
Is mirtazapine safe for dogs with kidney disease?
It is commonly used and was well tolerated in the studies available [2][6]. Safety depends on your dog's other conditions and medications. Your veterinarian will decide if it is appropriate for your dog.
What if my pet's blood pressure is normal but the veterinarian still prescribes amlodipine?
This can happen when a pet has protein loss in the urine or other kidney changes that benefit from blood pressure control. Your veterinarian is treating the whole picture, not one number. Ask for the target range so you know what success looks like.
Related Articles
- mirtazapine for dogs
- Dog Kidney Disease Diet
- Mirtazapine Appetite Stimulant: Dose for Cats and Dogs Guide
- Canine Chronic Kidney Disease: Staging and Therapeutic Plan
- Canine Chronic Kidney Disease: Staging, Diagnosis, and Management
- Dog Bad Breath Kidney Disease
- Amlodipine for Cats With Kidney Disease: Safe Use
- Amlodipine for Dogs and Cats: Uses and Safety
- High Blood Pressure and Kidney Disease in Dogs
- Urine Protein-to-Creatinine Ratio Interpretation in Renal Disease
- Chronic Kidney Disease Pathophysiology Explained
References
- Use of amlodipine in the treatment of cats with systemic hypertension in Japan. The Journal of veterinary medical science, 2024.
- Evaluation of the Short-Term Effects of Mirtazapine on Appetite Stimulants in Dogs: A Retrospective Study and a Placebo-Controlled Trial. Animals : an open access journal from MDPI, 2025.
- Oral mirtazapine decreases the gastrointestinal adverse effects in cats on doxorubicin chemotherapy. Veterinary journal (London, England : 1997), 2024.
- Effect of amlodipine on the circulating renin-angiotensin-aldosterone system in healthy cats. Journal of veterinary internal medicine, 2024.
- Overcoming mirtazapine's therapeutic limitations in veterinary practice: Development of a taste - masked orally disintegrating tablet with microsphere-based controlled release. Veterinary journal (London, England : 1997), 2026.
- Use of mirtazapine in the treatment of canine behaviour problems: A review of 32 cases. The Veterinary record, 2024.
- Pharmacotherapeutics in Glomerular Diseases in Animals - Pharmacology. Merck Veterinary Manual.