A well-known erectile dysfunction drug might just have added benefits for dogs, too. A recent study suggests that liquid sildenafil, the active ingredient in Viagra, may help treat dogs with an enlarged esophagus that makes them unable to eat food easily and can sometimes prove fatal. More research will be needed to confirm the drug’s benefits for these dogs, however.
The condition is known as megaesophagus. It can affect many mammals, humans and dogs included, and can be caused by other diseases. The esophagus, the tube that carries food from the mouth to the stomach, not only becomes enlarged but also loses its ability to push down food. This leads to food and water getting stuck in the esophagus, and dogs will often regurgitate a meal before it can reach the stomach. Because afflicted dogs aren’t getting much actual nutrition, the condition can lead to slow starvation. Other times, bits of food will go down the windpipes to the lungs instead, causing a form of pneumonia that can turn deadly if untreated.
Vets usually try to handle megaesophagus by treating the underlying conditions if possible. Dietary changes or feeding dogs upright can also sometimes reduce the risk of regurgitation, and in more severe cases, dogs may be given a feeding tube directly to their stomach. But there are no specific drugs available that are thought to help restore the esophagus’s ability to work as usual.
Sildenafil primarily affects the body by relaxing, or dilating, blood vessels. Though this helps men with erectile dysfunction, it’s also used to treat a form of high blood pressure in both humans and dogs. The drug’s dilation effects made the authors of this recent study, published last month in the American Journal of Veterinary Research, wonder if it could help with megaesophagus too.
Their small study involved 10 pet dogs with the condition. For two weeks each, the dogs were randomized to receive a course of liquid sildenafil and a course of placebo (if a dog was given the placebo first, for instance, they would get the sildenafil afterward after a week-long break, and vice-versa). Before and at the start of either treatment, the authors measured via X-ray how well the esophagus functioned at moving food down to the stomach. They asked owners to keep track of how many episodes of regurgitation the dogs had at home over the next two weeks.
The authors didn’t find a significant difference in how fast the esophagus moved food along in either scenario. But when the dogs were on sildenafil, the owners reported fewer bouts of regurgitation compared to baseline and to when they were on placebo. The dogs also gained some weight back (about 2 pounds on average) while on sildenafil, and there didn’t appear to be any major side effects reported.
“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-author Jillian Haines, a veterinarian at Washington State University, told local media outlet KOIN. “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.”
Haines says that she’s since prescribed sildenafil to some of the owners involved in the study, who are continuing to use it with their dogs. But more research will have to be done to validate the possible benefits seen in this small study, and the drug may not work well for all affected dogs. In the study itself, sildenafil reached the dogs’ stomachs only 70% of the time, and it seemed to be less effective for dogs that were more frequently regurgitating to start with.
Still, given the limited options available for this condition, the team hopes that more veterinary researchers will be able to follow up on their work.
“I think sildenafil will be life-changing and life-saving for a lot of dogs,” Haines said. “This research helps support its use and hopefully will encourage more people to use it.”