When we treat heartworm disease there is really only one medication that most vets reach for, called Immiticide (melarsomine). It first came out in the mid-1990s, replacing the previous drug of choice, Caparsolate. The latter drug isn't used by most vets anymore because it runs a higher risk of side-effects and can cause significant tissue damage if it gets outside of the vein. Immiticide is much safer and less irritating, making it the gold standard for around 15 years.
For the last two years Immiticide has been in short supply because of ingredient shortages and other manufacturing problems. Currently it is only manufactured by one pharmaceutical company, Merial, and they have limited sources of the ingredient. For the last two years when we wanted to treat a pet we had to directly contact the company, discuss the case, and get them to ship it directly rather than ordering it through typical distributing systems. This method allowed Merial to keep the supply going to pets that really needed it rather than sitting unused on vets' shelves. It was a real hassle to us vets, but I never ran into a problem getting it when I needed it.
That is changing. A couple of weeks ago Merial announced further problems to the point of them not being able to produce any more Immiticide for the foreseeable future. The only product left is what is sitting on shelves in offices and warehouses, and that will quickly be depleted. Merial is hoping to have more available within seven months, but there is no promise this is the case. So treatment is now being withheld from mild cases without symptoms and being reserved only for severe cases.
This is extremely frustrating, and keeps us from providing the best care for pets. I also think it's crazy that we are so dependent on one single source for such an important medication, leading to situations like we currently have. Honestly I don't know all of the details behind Merial's problems, but with a shortage being known for about two years I would have hoped that someone would have come up with alternative sources by now.
This means that many people who have their dogs diagnosed with heartworms will have to go without proper treatment, instead relying on symptomatic control and other secondary treatments that aren't as fast or effective. However, keep in mind that this is a completely preventable disease! There is no reason for dogs NOT to be on heartworm prevention. So a solution is pretty simple from one aspect...use prevention and your dog's won't get the disease!
And let's hope that this shortage ends soon.