By Rania Gollakner, BS, DVM, MPH

What is imipramine?

Imipramine (brand names: Tofranil®, Impril®) is a tricyclic antidepressant used to treat urinary incontinence, sudden muscle weakness, and certain behavior disorders. It may also be used in conjunction with other medications to treat chronic pain. In horses, it has been used for narcolepsy and ejaculatory dysfunction.

Its use in cats, dogs, and horses to treat behavior and medical conditions 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 imipramine given?

Imipramine is given by mouth in the form of a tablet or capsule. It may also be compounded into an oral liquid to be given by mouth or injectable liquid to be used in the clinic setting. It may be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food. Measure liquid forms carefully. Do not give this medication in conjunction with aged cheese or while using amitraz-containing flea/tick collars. Allow free access to water while giving this medication.

This medication can take up to a few weeks before full effects are noted, and at times improvement may not be visibly obvious; your veterinarian may need to run further tests to determine if the drug is working appropriately.

What if I miss giving my pet the medication?

If you miss giving your pet a dose, give the next dose as soon as you remember, but if it is closer than 12 hours before the next scheduled dose, either:

  1. skip the dose you missed, give it at the next scheduled time, and continue with the regular dosing schedule, OR
  2. give the missed dose and then wait the recommended interval before giving the next dose (continue giving it regularly at that new time).

Are there any potential side effects?

Studies are limited for this medication and therefore information regarding side effects is also limited. However, common side effects are typically similar to other tricyclic antidepressants and include sleepiness, dry mouth, and constipation. Other side effects may include diarrhea, vomiting, or trouble urinating. Serious side effects include excitability, shaking, seizures, bleeding, fever, fast heartbeat, weakness, or collapse.

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?

Do not use this medication in pets that are allergic to it or other tricyclic antidepressants. Do not use this medication concurrently with monoamine oxidase inhibitors (MAOIs). Do not use in pets that are pregnant or nursing. Use cautiously in pets that are very young or old, or in pets with seizures, diabetes, adrenal gland problems, glaucoma, dry eye syndrome (KCS), or liver, thyroid, or heart disease.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with imipramine: albuterol, alprazolam, anticholinergic agents, cimetidine, cisapride, clonidine, CNS depressants, cyclobenzaprine, linezolid, metoclopramide, nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, phenobarbital, phenothiazines, quinidine, rifampin, selective serotonin reuptake inhibitor (SSRIs), sympathomimetic agents, MAOIs, thyroid agents, or tramadol.

Imipramine may also interact with blood glucose testing.

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

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 at home for serious side effects.

How do I store imipramine?

Store the tablets and capsules at room temperature and protect from light. For compounded forms, follow the storage instructions on the label.

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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