October 2011 This is not the first incident of an Immiticide shortage. However, this shortage is particularly worrisome for pet owners and veterinarians. Merial, the company that produces this FDA-approved drug for heartworm treatment in dogs, has provided little information regarding the shortage.

The company announced that technical difficulties at the manufacturing plant are responsible for the shortage. In addition, the company has not issued a statement advising how long this shortage may continue. The company delivered more disheartening news when it announced its stock of Immiticide is depleted.

Merial is currently seeking alternative sources for this life saving medicine for dogs who need treatment for infection with adult heartworms. You can read a copy of their letter to vets in this this pdf published on the FDA site – it is a three page document and took a little while to open on my computer.

Unfortunately, Immiticide is the only FDA-approved treatment for heartworms in the United States. It is the only heartworm treatment that is proven safe and effective.

The shortage is critical and the FDA has given Merial the authorization to import Immiticide from an approved European supplier. However, the European supplier has limited quantities available for export to the United States. The available quantities from the European supplier will only meet a fraction of the demand in the United States.

Veterinarians normally maintain a significant supply of Immiticide. However, due to the shortage Merial has advised veterinarians they can only order Immiticide on a case-by-case basis. This shortage is troublesome and far more critical than past shortages.

Advice for Pet Owners During this Immiticide Shortage

● If your dog is on preventative heartworm treatment, continue the treatment diligently. The best course of action in this shortage is prevention.

● If your dog is not on a preventative treatment, seek the advice of a veterinarian immediately. Your pet should be tested for heartworms before starting a preventive treatment medicine. If your pet tests negative, preventative heartworm treatment can commence immediately. However, your dog should be tested again after six months. The heartworm test indicates a positive result if adult heartworms are present in the heart. It does not detect the adult heartworms that have not yet travelled to the heart through the bloodstream. A dog can test negative initially and test positive six months later.

● If your dog has tested positive, your veterinarian will have to submit documentation to Merial for approval of a supply of Immiticide. However, Merial may decline your veterinarian’s request. The denial or approval will depend on the extent of the infection and the immediate danger it presents. If your dog is not approved for the required dose of Immiticide, veterinarians have established a protocol to help your pet survive until the shortage is resolved. These alternative treatments may not be successful in eliminating the adult heartworms, but the treatments will help your dog survive an infection until Immiticide is available.

● The American Heartworm Society strongly recommends limiting the physical activity of infected dogs. A dog’s physical activity can increase the severity of the heartworm infection. If your dog is infected with adult heartworms limit your dog’s physical activity as much as possible.

Your veterinarian will prescribe a preventative heartworm medicine to kill the larvae (immature heartworms). This will prevent further infection of adult heartworms in the heart, but it will not kill the adult heartworms that already exist in the heart.

Visit your dog’s veterinarian for advice and prevention options. Most veterinarians are keeping pet owners informed of this critical situation through newsletters or online blogs. While this shortage of Immiticide continues, a preventative heartworm medicine is crucial.