# Transdermal and Liquid Meds for Cats: Zonisamide and Benazepril Compounded transdermal gels and liquid medicines can help when a cat is hard to pill, but they are not a simple swap for every drug. Transdermal zonisamide for cats is sometimes used for seizures, and transdermal benazepril is sometimes used for heart or kidney problems, yet absorption through cat skin is unpredictable and varies by drug, by formula, and by cat. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Zonisamide is an antiseizure medicine. In one study of 57 cats, oral zonisamide reduced seizures by a median of 1 seizure per month and 1 seizure day per month [1]. - Benazepril is an ACE inhibitor used for heart and kidney conditions. It is often given more than once daily for best effect, which can make compliance harder [2]. - Transdermal absorption is not equal across drugs. Some medicines, like mirtazapine, have good owner-reported results when applied to the ear, but that does not mean every drug absorbs well that way [3]. - Your veterinarian decides the dose, the form, and the schedule based on your cat's weight, condition, and other medicines. - Never switch from a pill to a gel, or change the dose, without talking to your veterinarian first. ## What Are Zonisamide and Benazepril? Zonisamide is an antiseizure medication. Veterinarians use it in cats with seizures, especially when phenobarbital alone does not control seizures well or when a cat cannot safely take phenobarbital [1]. In a Japanese referral hospital study, three cats with idiopathic epilepsy were treated with zonisamide alone, and two of them reached the treatment goal of fewer than one seizure every three months [4]. Two of three cats on phenobarbital plus zonisamide also reached that goal [4]. Benazepril is an angiotensin-converting enzyme (ACE) inhibitor. It is used in cats with chronic kidney disease to reduce protein loss in urine, and it is also used in cats with certain heart conditions [2]. For a given daily dose, benazepril works better when it is given several times a day, but frequent dosing can lower compliance [2]. That is one reason owners and veterinarians look for easier options. Compounded transdermal medicines are custom-made gels or ointments that are rubbed onto the inner surface of the ear. Compounding lets a pharmacy create a form or flavor that is not sold commercially [5]. A liquid is another compounded option, usually given by mouth. Both forms exist because pilling a cat can be hard on everyone. ## How Do These Medicines Work? Zonisamide works by stabilizing electrical activity in the brain. It is metabolized mainly by liver enzymes called CYP450 [6]. In dogs, when zonisamide is given with phenobarbital, zonisamide is cleared faster and its half-life gets shorter [6]. The same interaction has not been fully worked out in cats, but it is one reason your veterinarian may adjust doses or check drug levels when two antiseizure medicines are used together. For more on testing drug levels, see [Therapeutic Monitoring of Antiepileptic Drugs in Dogs and Cats](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/therapeutic-monitoring-antiepileptic-drugs-dogs-cats). Benazepril blocks ACE, an enzyme that tightens blood vessels and drives hormone changes that stress the heart and kidneys. Blocking it lowers blood pressure inside the kidney's filtering units and reduces protein leaking into urine [2]. In a study of a benazepril-containing renal diet, cats eating the medicated diet had lower total drug exposure than cats given once-daily tablets, yet ACE inhibition was at least as good in cats with chronic kidney disease and even better in healthy cats [2]. That finding shows how much the delivery method can change drug behavior. Transdermal absorption depends on the drug's molecule size, how much it dissolves in fat, and the condition of the skin. The ear pinna is thin and has good blood flow, which is why it is the usual application site. Even so, a gel that works for one drug may fail for another. Mirtazapine transdermal ointment is a well-studied example. In a survey of 70 owners, 97% said applying it to the ear was easy, 91% alternated ears as directed, and 77% thought it worked to stimulate appetite [3]. That success does not automatically transfer to zonisamide or benazepril. ## Dosing Basics for Transdermal Zonisamide and Benazepril in Cats ### Who Decides the Dose? Your veterinarian does. The dose depends on your cat's weight, kidney and liver health, seizure frequency, other medicines, and the concentration of the compounded product. Compounded gels are not standardized the way commercial pills are, so two pharmacies can make products that behave differently. Never measure or guess a dose yourself. ### How Is It Given? For a transdermal gel, you part the fur on the inner ear, place the measured amount on the skin, and rub it in gently. Wear gloves if your veterinarian or pharmacist tells you to. Alternate ears unless told otherwise, since owners in one survey who alternated ears reported good results with that routine [3]. For a liquid, use the syringe or dropper provided by the pharmacy, not a kitchen spoon. If your cat fights the liquid, ask about flavoring or a different form. Wash your hands after handling any compounded medicine. Keep the tube or bottle capped and store it as the label directs. If you have other pets or children, keep the product out of reach, since these are human drugs in concentrated form. ### What About a Missed Dose? If you miss a dose, do not double up. Give the next dose at the regular time unless your veterinarian gave you different instructions. For seizure medicine, missed doses can trigger breakthrough seizures, so call your veterinarian if you miss more than one dose or if you cannot keep the medicine down. For benazepril, a single missed dose is usually less urgent, but repeated gaps can reduce the drug's benefit [2]. ## Side Effects: What to Watch For | Side effect | How common or serious | What to do | |---|---|---| | Sleepiness, wobbliness, poor appetite | Common with zonisamide in cats, usually mild | Note the timing and call your vet if it lasts more than a day or two | | Vomiting or diarrhea | Possible with either medicine | Call your vet if it repeats or your cat stops eating | | Increased vocalization, ear redness, restlessness | Reported in about 20% of owners using transdermal mirtazapine, a different drug [3] | Check the ear, stop if the skin is raw, and call your vet | | Low blood pressure, weakness, fainting | Uncommon with benazepril but serious | Emergency visit right away | | Worsening kidney values | Possible with benazepril, which is why bloodwork is checked | Keep scheduled lab appointments | | Increased seizures | Possible if a dose is missed or a drug level is too low | Call your vet the same day | Zonisamide can raise phenobarbital levels in dogs, sometimes above the range linked to liver toxicity, which required dose reductions in that report [6]. If your cat takes both drugs, your veterinarian may check phenobarbital levels more often. For general information on sedating or calming medicines in cats, see [Gabapentin For Cats](/knowledge/veterinary-medicine/clinical-methods/gabapentin-for-cats) and [Benadryl Diphenhydramine Cat Dose: Feline Allergy and Sedation Guide](/knowledge/veterinary-medicine/calculators-clinical-tools/benadryl-diphenhydramine-cat-dose-feline-allergy-and-sedation-guide). ## Who Should Not Take These Medicines, and What Interacts With Them? Cats with known liver disease need extra caution with zonisamide because it is broken down by liver enzymes [6]. Cats with dehydration, low blood pressure, or certain kidney problems may not be good candidates for benazepril. Pregnant or nursing cats, and cats with a history of reactions to either drug, should not receive them without a clear discussion with your veterinarian. Drug interactions matter. Zonisamide and phenobarbital interact in dogs, with phenobarbital levels rising after zonisamide is added [6]. Benazepril can interact with diuretics, other blood pressure medicines, and potassium supplements. Always tell your veterinarian about every product your cat gets, including supplements and over-the-counter items. If you use a compounded gel, tell the veterinarian the exact concentration and pharmacy so the dose can be checked. ## Overdose and When to Call for Help If your cat licks off a full dose of gel, chews the tube, or drinks the liquid, treat it as a possible overdose. Signs can include severe sleepiness, wobbling, vomiting, a slow heart rate, or collapse. Call your veterinarian or a pet poison control service right away. Two options in the United States are the ASPCA Animal Poison Control Center at (888) 426-4435 and the Pet Poison Helpline at (855) 764-7661. A consultation fee may apply. Do not wait for symptoms to appear. Bring the product packaging with you so the veterinary team knows the drug, the strength, and the amount involved. If your cat stops breathing or cannot be woken, go to an emergency clinic immediately. ## Limitations and When to Contact a Veterinarian Compounded transdermal medicines are not FDA-approved products, and their absorption can differ from batch to batch and cat to cat. A gel that seems to work may still deliver less drug than a pill, and a liquid may deliver more. That is why response is judged by results, not by how easy the routine feels. Contact your veterinarian the same day if your cat has more seizures than usual, seems sedated or unsteady, refuses food for more than 24 hours, or develops redness or crusting on the ear where the gel is applied. Go to an emergency clinic now if your cat has a seizure that lasts more than a few minutes, has repeated seizures without recovering, collapses, breathes with an open mouth, or cannot be roused. Schedule a routine visit if you notice a slow decline in appetite, weight, or energy, or if refilling the prescription is coming due and you are unsure the medicine is helping. Every cat is different, and only your veterinarian can judge whether a compounded transdermal or liquid form is right for your cat. Bring your questions and your observations to each visit. ## Frequently Asked Questions ### Can I switch my cat from zonisamide pills to a transdermal gel on my own? No. Ask your veterinarian first. The dose and the expected absorption are different between forms, and a switch can change seizure control. Your veterinarian may want to adjust the amount or check drug levels after the change. ### Is a liquid easier to give than a gel? It depends on your cat. Some cats accept a flavored liquid more easily, while others fight anything near the mouth and do better with an ear gel. Owners in one survey found ear application easy and often preferred it to the oral form, though cost was a drawback for some [3]. ### How long does it take to know if the medicine is working? For seizures, veterinarians usually track seizure frequency and seizure days over weeks to months. In one study, cats on zonisamide showed a median drop of about one seizure per month [1]. For benazepril, kidney and heart benefits are judged with repeat bloodwork, urine tests, and exams over time [2]. ### Can I use the same gel for two different medicines? No. Each compounded product is made for one drug at one strength. Mixing or sharing products can give the wrong dose. Keep each tube labeled and separate, and ask your pharmacist if you are unsure which product goes on which ear. ### What if my cat hates having its ears touched? Tell your veterinarian. There are other options, including flavored liquids, pills hidden in food, or a different medicine. For step-by-step help with ear gels, see [How to Give Your Cat a Transdermal Medication: Tips for Success](/knowledge/veterinary-medicine/pet-medication-guide/how-to-give-your-cat-a-transdermal-medication-tips-for-success). ## Related Articles - [Gabapentin For Cats](/knowledge/veterinary-medicine/clinical-methods/gabapentin-for-cats) - [Therapeutic Monitoring of Antiepileptic Drugs in Dogs and Cats](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/therapeutic-monitoring-antiepileptic-drugs-dogs-cats) - [Benadryl Diphenhydramine Cat Dose: Feline Allergy and Sedation Guide](/knowledge/veterinary-medicine/calculators-clinical-tools/benadryl-diphenhydramine-cat-dose-feline-allergy-and-sedation-guide) - [How to Give Your Cat a Transdermal Medication: Tips for Success](/knowledge/veterinary-medicine/pet-medication-guide/how-to-give-your-cat-a-transdermal-medication-tips-for-success) - [Revolution Plus for Cats: Selamectin Sarolaner Feline Dose Guide](/knowledge/veterinary-medicine/calculators-clinical-tools/revolution-plus-for-cats-selamectin-sarolaner-feline-dose-guide) - [Cat Anxiety Medication: What You Need to Know](/knowledge/veterinary-medicine/anxiety-and-behavior-support/cat-anxiety-medication) - [Zonisamide for Cats: Dosage and Side Effects](/knowledge/veterinary-medicine/pet-medication-guide/zonisamide-for-cats) - [Benazepril for Cats: Uses for CKD and HCM](/knowledge/veterinary-medicine/pet-medication-guide/benazepril-for-cats-ckd-hcm) - [Transdermal and Liquid Fluoxetine or Mirtazapine for Cats](/knowledge/veterinary-medicine/pet-medication-guide/transdermal-liquid-fluoxetine-mirtazapine-cats) ## References 1. [A retrospective study of the efficacy of zonisamide in controlling seizures in 57 cats](https://pubmed.ncbi.nlm.nih.gov/38240116/). Journal of veterinary internal medicine, 2024. 2. [Why incorporating benazepril into a renal diet may improve treatment efficiency and compliance in cats with chronic kidney disease](https://pubmed.ncbi.nlm.nih.gov/42818666/). Frontiers in veterinary science, 2026. 3. [Owner's Perspective About the Use of Mirtazapine Transdermal Ointment in Cats-A Survey-Based Study](https://pubmed.ncbi.nlm.nih.gov/41153979/). Animals : an open access journal from MDPI, 2025. 4. [Evaluation of antiseizure medications including zonisamide in feline idiopathic epilepsy at a referral hospital in Japan](https://pubmed.ncbi.nlm.nih.gov/37614732/). Open veterinary journal, 2023. 5. [Pharmaceutical Compounding in Veterinary Medicine: Suspension of Itraconazole](https://pubmed.ncbi.nlm.nih.gov/38794238/). Pharmaceutics, 2024. 6. [The effect of oral zonisamide treatment on serum phenobarbital concentrations in epileptic dogs](https://pubmed.ncbi.nlm.nih.gov/38868500/). Frontiers in veterinary science, 2024. ## Further Reading - [Bnp Ointment for Cats (Pet Poison Helpline)](https://www.petpoisonhelpline.com/uncategorized/bnp-ointment-for-cats/) - [Bnp Ointment for Cats 2 (Pet Poison Helpline)](https://www.petpoisonhelpline.com/uncategorized/bnp-ointment-for-cats-2/) - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners)