Sildenafil, the generic version of Viagra, could be a treatment for a rare condition found in dogs called megaesophagus. This condition makes the canine esophagus expand and lose the ability to deliver food to the stomach.

Dogs with megaesophagus often develop even more ailments, and many have to be put down. Often, as they eat, the food is regurgitated and enters their lungs, causing aspiration pneumonia. As reported in the American Journal of Veterinary Research, the same principle that allows sildenafil to treat erectile dysfunction helps dogs.

The drug leads to smooth muscle relaxation, allowing the lower esophagus to open and let the food pass, leading to a reduction in regurgitation. There were minimal side effects, and the dogs treated gained weight during those two weeks.

“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,” co-lead author Dr Jillian Haines, from Washington State University, said in a statement.

“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.”  

10 dogs with this condition were enrolled in the study. They were administered either a placebo or sildenafil for two weeks at a time, then they were given neither for a week, and then swapped groups for the following two weeks. The owners were tasked with tracking episodes of regurgitation.

Moving X-ray analysis of the dogs eating after being given either the drug or placebo didn’t show much difference – but nine out of 10 owners reported reduced regurgitation during the two weeks when the pooches were given liquid sildenafil.

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

“Moderately affected dogs that were regurgitating frequently but not excessively seemed to see the most dramatic results. I actually prescribed sildenafil to several of those patients after the study, and they are still using it today.”

Dogs with more severe signs of the disease didn’t benefit as much, given it was more difficult for them to have the drug reach the stomach. An unfortunate catch 22. Sildenafil is already prescribed to humans and dogs to treat elevated blood pressure in the lungs. It might have even more applications beyond this and treating megaesophagus.

“A lot of veterinarians are reaching out and asking about this drug,” Haines said. “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.”