Cyproheptadine for Dogs and Cats: Uses and Side Effects

Cyproheptadine is a prescription antihistamine that veterinarians commonly prescribe as an appetite stimulant in cats and, in certain situations, to help treat serotonin syndrome in dogs and cats.

Although it is FDA-approved for people, it is prescribed extra-label in veterinary medicine.

Here’s how cyproheptadine works, when it’s prescribed, possible side effects, dosing guidance, and important safety information.

What Is Cyproheptadine?

Cyproheptadine is a prescription antihistamine most commonly used as an appetite stimulant in cats and dogs. Veterinarians may also prescribe it as part of the treatment for serotonin syndrome.

Unlike some antihistamines, cyproheptadine is not used to relieve itching associated with allergies in dogs and cats or to manage asthma in cats.

FDA approval: Cyproheptadine is FDA-approved for human use as a generic medication. Although it is not FDA-approved as a veterinary medication, veterinarians may legally prescribe it extra-label (off-label) when appropriate.

Compounded cyproheptadine: In some cases, your veterinarian may recommend a compounded formulation when:

• Your pet has difficulty taking the commercially available formulation.
• The required dosage strength is not commercially available.
• Your pet is allergic to an ingredient in the FDA-approved medication.

Compounded medications are not FDA-approved. They are prepared by a veterinarian or licensed pharmacist to meet an individual patient's specific needs.

Safety Considerations for Cyproheptadine

Cyproheptadine is not appropriate for every pet and should be avoided in animals with certain medical conditions.

Do not use cyproheptadine in pets with:

• Urinary obstruction
• Gastrointestinal obstruction
• Glaucoma (elevated eye pressure)

Before starting cyproheptadine, tell your veterinarian about all of your pet's medications and medical conditions, as drug interactions may increase the risk of side effects.

How Cyproheptadine Works

Cyproheptadine works by blocking the effects of serotonin in the brain, helping stimulate appetite and reduce the effects of excess serotonin.

When the hypothalamus, a region of the brain involved in regulating appetite, is exposed to serotonin, appetite is suppressed. Cyproheptadine blocks serotonin from binding to receptors in the hypothalamus, which helps stimulate appetite.

Because it blocks serotonin, cyproheptadine is also useful in treating serotonin syndrome, a condition caused by excessive serotonin activity in the brain.

How To Give Cyproheptadine

Give cyproheptadine exactly as directed by your veterinarian.

Administration tips:

• Follow the directions on the prescription label or those provided by your veterinarian.
• Cyproheptadine may be given with or without food.
• Giving the medication with food may help reduce the risk of digestive upset.

Missed a Dose?

If you miss a dose of cyproheptadine, contact your veterinarian for guidance. In many cases, they may recommend giving the missed dose when you remember. 

However, if it is almost time for your pet's next scheduled dose, they may advise skipping the missed dose and resuming the normal dosing schedule.

Do not give extra or double doses.

Cyproheptadine Side Effects

Cyproheptadine is generally well tolerated, but side effects can occur.

Possible side effects include:

• Drowsiness, which often becomes less noticeable over time
• Hyperexcitability (especially in cats)
• Dry mouth
• Abnormally high heart rate
• Difficulty urinating due to urinary retention

Human Side Effects

Cyproheptadine is also a prescription medication for people, but human and veterinary doses differ. Pets should never receive medication prescribed for humans.

If you accidentally ingest a pet medication, contact your physician immediately or call the National Poison Control Center at 800-222-1222.

When To Call Your Veterinarian

Contact your veterinarian if:

• Your pet develops severe side effects.
• Your pet's condition worsens or does not improve with treatment.
• You suspect your pet has received an overdose.
• You have additional questions or concerns about using cyproheptadine.

Cyproheptadine Overdose

A cyproheptadine overdose can cause serious neurologic and cardiovascular side effects and requires immediate veterinary attention.

Signs of an overdose may include:

• Sedation
• Hyperexcitability
• Seizures
• Dry mouth
• Abnormally high heart rate
• Difficulty urinating due to urinary retention
• Fever
• Low blood pressure

If you suspect your pet has received an overdose, contact your veterinarian immediately, seek emergency veterinary care, or contact an animal poison control center. Consultation fees may apply.

• Pet Poison Helpline: (855) 764-7661
• ASPCA Animal Poison Control: (888) 426-4435

How To Store Cyproheptadine

Store cyproheptadine according to the product label to help maintain its safety and effectiveness.

Storage instructions:

• Store cyproheptadine at controlled temperatures between 68 F and 77 F (20 C–25 C).
• Keep the container tightly closed to protect the medication from moisture and light.
• Store compounded formulations according to the instructions provided by the compounding pharmacy.
• Keep out of reach of children and pets.