Viagra shows promise as a treatment for dogs with often-fatal eating disorders

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Sildenafil, the generic version of the drug known as Viagra, could be the long-awaited cure for a group of dogs with a rare disease called megaesophagus, according to a US study.

The condition involves an enlargement of the esophagus and a loss of the organ’s ability to move food into the stomach, which lets food accumulate in the lower esophagus. If left untreated, many animals regurgitate their food and suck food into their lungs, causing aspiration pneumonia.

“The literature tells us that many dogs with the disease die of aspiration pneumonia or are humanely euthanized due to poor quality of life within eight months of diagnosis,” said Dr. Jillian Haines, veterinarian at Washington State University who co-led the study, published in the American Journal of Veterinary Research.

Liquid sildenafil has been shown to relax the smooth muscle of the lower esophagus so that it opens up to allow food to pass into the stomach. Apart from a few rare gastrointestinal irritations, there are no side effects at the dose used in the study.

While sildenafil is best known for treating erectile dysfunction, the drug is also used to treat high pulmonary arterial pressure in dogs and humans.

“If you look at the literature, there are no drugs that we can use to manage megaesophagus. Sildenafil is the first to target these mechanisms and reduce regurgitation, which is important because that’s what that ultimately kills these dogs,” Dr. Haines said.

“It opens the lower esophageal sphincter for 20 minutes to an hour, which works really well for dogs because we only want it to open when they eat.”

Dr. Haines and his team used videofluoroscopy to monitor liquids and later wet mixed foods as they moved through the esophagus.

Ten dogs with megaesophagus enrolled in the study received either a placebo or sildenafil for two weeks at a time. The dogs then went for a week without any medication. Then the placebo and sildenafil groups were reversed.

Their owners were instructed to record the regurgitation episodes but were not told what drug their dog had taken.

There was no significant difference between placebo and sildenafil during a 30-minute videofluoroscopy, where vets use a moving x-ray to look at how food is swallowed. However, the study found that nine out of 10 owners reported reduced regurgitation during the two weeks the liquid sildenafil was administered.

“In many cases, owners were able to determine which drug sildenafil was because it worked,” Dr. Haines said.

Enrolled dogs also gained an average of just over two pounds by the end of the study.

“Moderately affected dogs that regurgitated frequently but not excessively seemed to see the most dramatic results,” Dr. Haines said.

Dogs that showed severe signs of the disease did not show such positive results. In these cases, the researchers found that it was more difficult to get the drug into the stomach for absorption.

Although the study is promising, there is still a lot to know about the drug. Dr. Haines hopes that future studies will investigate the use of sildenafil in veterinary medicine.

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