Study shows Viagra as promising treatment for canine megaesophagus

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A study¹ conducted at the Washington State University (WSU) College of Veterinary Medicine published in the American Journal of Veterinary Research has revealed that sildenafil—the generic version of the drug Viagra—could be the anticipated remedy for dogs with the rare disorder, megaesophagus.

According to a university release,2 megaesophagus consists of an enlargement of the esophagus and a loss of the organ’s ability to transport food to the stomach, resulting in food accumulating in the lower esophagus. When left untreated, animals may regurgitate their food and aspirate food into their lungs, causing aspiration pneumonia.

“The literature tells us that many dogs with the disease die from aspiration pneumonia or humanely euthanized due to poor quality of life within eight months of diagnosis,” said Jillian Haines, DVM, an associate professor at WSU who co-led the study, in the release.²

“If you look at the literature, there are no drugs we can use to manage megaesophagus. Sildenafil is the first to target these mechanisms and reduce regurgitation, which is big because that’s what ultimately kills these dogs,” added Haines. “It opens the lower esophageal sphincter for 20 minutes to an hour, which works really well for dogs because we only want that to open when they are eating.”

The details

Susan Mehain, DVM, MS, and Sarah Guess, DVM, DACVIM (SAIM), MS, co-led the study with Haines. The trio used videofluoroscopy—a moving X-ray to analyze how food is swallowed to monitor liquid and later, blended wet food as it moved down the esophagus.

The research¹ demonstrated that liquid sildenafil could relax the smooth muscle of the lower esophagus, enabling it to open and let food pass to the stomach. Except for some rare gastrointestinal irritation, there were no side effects to canines at the dose used in the study.

The 10 dogs with megaesophagus who participated in the research were administered either a placebo or sildenafil for 2-week periods. The dogs then went a week without either drug. Then the placebo and sildenafil groups were switched. Their owners were asked to document regurgitation episodes but were unaware of which drug their dog had been taking.

There wasn’t a substantial difference between the placebo and sildenafil during a 30-minute videofluoroscopy. However, the study found that 9 out of the 10 owners documented decreased regurgitation during the 2 weeks when liquid sildenafil was administered.²

“In many cases, the owners were able to figure out which drug was sildenafil because it was working,” Haines commented.

In the release,² Hanes noted that dogs moderately affected by megaesophagus that regurgitated often but not excessively appeared to benefit the most and even prescribed sildenafil to some of those patients after the study. However, dogs that displayed severe signs of the disease didn’t show as positive of results and in those circumstances, the researchers discovered it was more challenging to get the drug into the stomach for absorption.

Though this research is promising, Haines remarked that there is still plenty to know about sildenafil and hopes future studies will examine its use in veterinary medicine.

“A lot of veterinarians are reaching out and asking about this drug,” Haines said, in the release.² “I think sildenafil will be life-changing and life-saving for a lot of dogs. This research helps support its use and hopefully will encourage more people to use it.”

References

1. Mehain SO, Haines JM, Guess SC. A randomized crossover study of compounded liquid sildenafil for treatment of generalized megaesophagus in dogs. 2022. doi:10.2460/ajvr.21.02.0030
2. Babcock J. Viagra promising as treatment for canine eating disorder. News release. Washington State University. February 21, 2022. Accessed February 22, 2022. https://news.wsu.edu/press-release/2022/02/21/viagra-promising-as-treatment-for-dogs-with-often-fatal-eating-disorder/