Question 18: Recently I have heard reports that ProHeart 6 has been recalled because of adverse reactions.  What does this recall mean, how does it affect my dog who has received ProHeart 6 in the past, and what I should do for future heartworm prevention?

Answer:  
            What does this recall mean:  On September 3, 2004, Fort Dodge Animal Health announced that it would voluntarily comply with the U.S. Food and Drug Administration (FDA) Center for Veterinary Medicine's request to temporarily cease production of and recall ProHeart 6.  ProHeart 6 is an injectable heartworm preventative that is administered to dogs by licensed veterinarians every 6 months.  The FDA has raised questions regarding the safety and effectiveness of ProHeart 6 and has formed an independent Advisory Panel to review the data.  Adverse reactions which have been suspected of being related to the administration of ProHeart 6 include allergic reactions, liver disease, heart disease, immune-mediated disease, bleeding abnormalities, cancer, and death.  Fort Dodge has compiled data which they believe firmly support their claims of safety.  The efficacy rate (effectiveness) of ProHeart 6 has been solidly documented at 99.997%.

According to Fort Dodge, one the biggest problems with this issue is that "potential adverse events reported to the FDA are unfiltered, meaning all reported potential events are submitted without regard to cause and effect.  Cases subsequently determined not to be related to the product remain in the overall reporting numbers, and are used to draw medical conclusions that dramatically overstate the incidence of various conditions."

Fort Dodge firmly believes that the rate of adverse reactions are well within expected limits.  For example, based on unfiltered reports with some reference to blood disorders or immune-mediated signs, the incidence rate for ProHeart 6 is 0.0025 percent or one in approximately 31,000 doses.  Research by Bronson (Am J Vet Res, Vol 43, No. 11, p. 2057-2059, 1982) reported that one percent of all deaths in dogs were due to hemolytic anemia (destruction of red blood cells by the body's own immune system).  Even using the unfiltered reporting numbers, ProHeart 6 is well below the baseline of disease for the U.S.  canine population. 

Many of the issues regarding ProHeart 6 arose as a result of reports in the media and on the internet.  Unfortunately the internet is full of reports that are often incorrect, anecdotal, overly emotional, unsubstantiated, and/or full of opinion and conjecture presented as fact.  Clients must be very careful when reviewing internet reports.

If you have other specific questions regarding ProHeart 6, we encourage you to speak to your veterinarian - there is no better source of information for you and your pet.  Please do not rely on the internet, friends, or word of mouth when it comes to this important issue.  For more detailed information from the manufacturer, go to www.proheart6.com and/or www.proheart6dvm.com.

How does the recall affect my dog who has received ProHeart 6 in the past:  At this time we are not administering any additional doses of ProHeart 6 to dogs until further notice.  Those dogs that have received ProHeart 6 in the past will need to switch to a different form of heartworm prevention (see below).  If you have concerns that your dog may be experiencing an adverse reaction as a result of ProHeart 6 administration you should contact your veterinarian or you may call Fort Dodge Professional Services department at 1-800-533-8536.

What I should do for future heartworm prevention:  Because your dog will not be receiving ProHeart 6 until further notice, you will need to switch to a different form of heartworm prevention.  You should start this preventative six months after your dog's last ProHeart 6 injection.  Other heartworm prevention options are summarized in FAQ number 5 and should be discussed with your veterinarian.

Update: ProHeart 6 has recently been relaunched in the United States, however, we do not currently carry the product in our clinic.