By Rania Gollakner, BS, DVM, MPH

What is tadalafil? 


Tadalafil (brand names: Cialis, Adcirca) is a vasodilator used to treat high blood pressure in the lungs. It is mainly used in dogs. Its use in dogs and occasionally cats to treat high blood pressure in the lungs 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 direction may be significantly different from those on the label.

How is tadalafil given?

Tadalafil is given by mouth in the form of a tablet or a compounded liquid. It may be given with or without food, however, if vomiting occurs when dosed on an empty stomach, give future doses with food. If vomiting continues, contact your veterinary office. Liquid doses should be measured very carefully. Some liquid forms must be shaken well before dosing. Read the label for further instructions.

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?

You should give the missed dose as soon as you remember, and then wait the recommended amount of time between doses. You should not give your pet two doses at once and do not give extra doses.

Are there any potential side effects?

Studies are limited for this medication and consequently, information regarding side effects is also limited. In humans, side effects include headache, indigestion, nausea, muscle aches, back pain, skin flushing, and nose congestion. Rarely, more serious side effects can occur such as blindness, deafness, and seizures. The significance of these effects in dogs is unknown. Side effects of sildenafil, a related drug, include skin flushing in the groin region, and gastrointestinal upset such as decreased appetite, vomiting, and diarrhea.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Studies in animals are limited for this medication and because of this, information regarding risk factors is also limited. In humans, tadalafil should not be used by those that are allergic to it or similar medications, or by those currently taking nitrate medications. For pets, use very carefully in these cases. Use cautiously and adjust doses in pets with liver or kidney disease. Safety during pregnancy and in pets that are nursing has not yet been established. Use cautiously and only when benefits outweigh the risks.

Are there any drug interactions I should be aware of?

The following medications should be used with special attention when given with tadalafil: alpha-adrenergic antagonists, amlodipine, azole antifungals, blood pressure medications, cimetidine, clarithromycin, erythromycin, nitrates, nitroprusside sodium, phenobarbital, phenytoin, or rifampin. 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?

Blood pressure in the lungs and in the body should be monitored regularly. Monitor your pet to be sure that the medication is working by noting improvements in ability to exercise, cough, breathing effort, or weight gain. Also, monitor for any side effects.

How do I store tadalafil?

Store this medication at room temperature between 59°F and 86°F (15°C and 30°C). For compounded forms of the medication, store according to 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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