There are some threads here on the Forum about the Proheart 6 injection, if you use the Search feature they will come up. One member lost her dog after he received it.
As Prism mentioned in her post, Proheart 6 was pulled from the market in 2004 due to adverse reactions to many dogs and several dying from it. It was released again back on the Market in 2008.
Here is the article about it- https://www.avma.org/News/JAVMANews/Pages/080715m.aspx
Here is a portion of an article from the FDA about it-
ProHeart 6 was approved in 2001, then voluntarily removed from the market in 2004 after reports of adverse events, including death, anaphylaxis, seizures, elevated liver enzymes, and immune-related blood problems. The FDA worked with the drug maker (at the time, Fort Dodge Animal Health), to develop a voluntary Risk Minimization Action Plan (RiskMAP) for ProHeart 6 that set several conditions in place, including restricted distribution of the drug to veterinarians who had completed specific training and certification, informed consent on the part of dog owners prior to treatment, revised product labeling with additional safety and risk information, and the establishment of certain criteria that dogs should meet to determine whether treatment with the drug was appropriate. The RiskMAP also encouraged veterinarians and pet owners to report adverse events associated with the product to the FDA. The drug sponsor also worked to eliminate residual solvents resulting from the manufacture of the product and that may have contributed to the reported adverse events. When ProHeart 6 returned to the market with the implementation of the RiskMAP, reports involving death, including reports of death associated with anaphylactic reactions, decreased. Since that time, the conditions imposed by the ProHeart 6 RiskMAP have been revised based on the FDA’s continued close monitoring of reports of adverse events. The drug maker has added ProHeart 12 to the existing RiskMAP for ProHeart 6 to ensure the safe use of both products.
You can view the entire article here, it also discusses Proheart 12 that has been released. https://www.fda.gov/animal-veterinar...m-disease-dogs
I would discuss your options with your Vet, certain preventatives work better than others based on where you live, your temperatures, weather conditions, etc.
I have used Heartgard Plus for many years, my guys have never had any problems, reactions etc., and they have always tested negative for HW at their yearly exam.
I prefer to use a monthly dose vs. a preventative that is for 6 months or longer.