By Rania Gollakner, BS, DVM, MPH

What is cyproheptadine?

Cyproheptadine (brand names: Periactin®, Ciplactin®, Cyheptine®, Cyprogin®, Cyprono®, Cyprosian®, Klarivitina®, Nuran®, Periactine®, Periactinol®, Peritol®, Polytab®, Practin®, Preptin®, Supersan®, Trimetabol®) is an antihistamine used to treat itchiness and allergic skin diseases. It is also used as an appetite stimulant in cats or to treat certain toxicities.

Its use in cats, dogs, horses to treat allergic conditions, toxicities, and stimulate appetite is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is cyproheptadine given?

Cyproheptadine is given by mouth in the form of a tablet or a liquid syrup. It may be given with or without food; however, if your pet vomits when dosed on an empty stomach, give future doses with food. Measure liquid forms carefully. Allow free access to fresh, clean water at all times while your pet is taking this medication.

This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose and you are giving this medication once daily, give it when you remember and then continue with the regular dosing schedule. If you are giving this medication twice daily, skip the dose you missed and give it at the next scheduled time. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Common side effects include sleepiness, increased appetite, and dry mouth. Cats may exhibit excitability rather than sleepiness. In horses, side effects may include mild depression, sleepiness, and lack of appetite. Uncommon side effects include vomiting, diarrhea, and decreased appetite.

This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Cyproheptadine should not be used in pets that are allergic to it or pets undergoing skin allergy testing within the next two weeks. It should be used cautiously in geriatric pets or those with enlarged prostate, overactive thyroid, urinary obstruction, severe heart disease, seizures, glaucoma, or gastrointestinal obstruction. Use cautiously in pregnant and lactating pets as safety has not been thoroughly established.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with cyproheptadine: cholinergic agonists, central nervous system depressant medications, mirtazapine, selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants, or tramadol.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

This medication may also interact with skin allergy testing, so discontinue this medication 2 weeks prior to allergy testing. It may also interact with certain thyroid levels (thyroid stimulating hormone).

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet for serious side effects. With long-term use, blood cell counts should be monitored.

How do I store cyproheptadine?

Store this medication at room temperature and protect from freezing. The liquid form may be stored in the refrigerator or room temperature.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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