Return to Pointer View home page September 24,  2004

Pet Alert: ProHeart 6 recalled by FDA concerns

Story and photo by Spc. Benjamin Gruver 
Staff Writer

ProHeart6 a preventative heartworm medication was recalled by Fort Dodge Animal Health of Overland Park, Kan. recently at the request of the Food and Drug Administration because of concerns about adverse reaction reports associated with the product.

The medication is a six-month injection to prevent heartworm disease known to be deadly to dogs and cats.

The disease is transmitted from infected pets to healthy ones through mosquito bites.

Heartworm larvae are injected from the mosquito into an animal’s blood stream, and then through a six-month maturation process the heartworms settle into the pulmonary artery in the heart.  

The FDA’s Center for Veterinary Medicine had received 5,552 adverse effect reports for the drug as of Aug. 4, 2004.

Fort Dodge Animal Health has cooperated with the FDA to investigate numerous reports since the product was approved in June 2001, including changing the label for safety information and now by recalling any product already distributed.

Further research will be conducted on ProHeart6 to determine the cause of the adverse reactions and develop a way to prevent such problems in the future.

“The recall has not been an issue for us,” said Capt. Anne E. Hessinger, West Point veterinarian, who said she doesn’t use the product, but may see cases from clients new to West Point. “We do get clients that come in who are PCSing all the time. So we do have clients who may have been administered ProHeart6 and we can look at their dog.”

According to Hessinger, the drug, ProHeart6, is made with the chemical Moxidectin that was originally used as an oral de-wormer to eliminate intestinal parasites in horses.

The two products used here, Hessinger explained, are Heartgard Plus and Interceptor. The products are both monthly oral medicines designed to kill off worms and contain the drugs Ivermectin and Milbemycin rather than Moxidectin.

Moxidectin has a narrow safety margin, but Ivermectin is a safe drug, explained Hessinger.

Ten times the dose of Ivermectin could be given with no ill effects, but ill effects have been found in horses with lower dosages of Moxidectin.

“I prefer to give a once a month medicine, and I like the satisfaction of giving them a dose and feeding them,” said Hessinger. “Also, as a horse vet, I work with horses a lot and have seen some of the adverse reactions and my personal preference is that I don’t like Moxidectin.”

Though it’s not required it’s highly recommended for pets to be on a prevention drug because heartworm disease is potentially deadly.

“It is inexpensive and easy to prevent, but very hard on the dog to treat the disease,” Hessinger said. “Medically it is not an easy thing to go through for treatment.”

 Hessinger explained that the treatment to kill off adult heartworms is a series of two shots within 24 hours for healthy large dogs, but what can be difficult is that because the worm is in the heart once it dies it has nowhere to go. The animal must dissolve the dead heartworms over time. 

Larger healthy dogs have a high success rate in returning back to normal, Hessinger explained, but smaller dogs, older dogs and dogs that are affected with clinical signs associated with heart worm disease such as coughing, lung inflammation and kidney failure have an increased risk for treatment.

The vet clinic here begins puppies as early as 12 weeks of age, and all that is required to begin preventative medicine is to be tested negative for heartworm disease.

“I keep my own dog on heart worm medicine year round,” Hessinger said. “We don’t have mosquitoes in the winter so there are people that take their animals off during the winter, but if you take your animal off in the winter then you have to get another blood test in the spring before you start up on the medicine again.”

Some signs to look for in animals that have the disease are coughing, exercise intolerance and being extra weak and tired.

“Coughing is a big thing because there is inflammation in the lung,” Hessinger said. “There are a lot of dogs that have no clinical signs, but have never been on heartworm medicine that will come in to get started and they’ll have heartworms.”

The cost for a heartworm test is $15 and the Heartgard Plus and Interceptor medicine for a larger dog costs approximately $5 a month.