Hi Patty,
Dori actually contacted them and was told this
“Hi losul and Shawna, I just spoke with tech support at Merial makers of Heartgard and was told that the ENTIRE dose must be given. You cannot split in half because they can not guarantee it’s efficacy. It is suggested that you not do that.”
Of course they would not suggest splitting doses for reasons other than efficacy. I just remember reading somewhere that to use a compounding pharmacy versus splitting the drug if pup is at the low end of dosing..
I did a quick google search and Mary Straus agrees with you and with Dori. “The issue of splitting heartworm pills comes up frequently. I have spoken to representatives from Merial (maker of Heartgard) and Novartis (maker of Interceptor). Both said that the active ingredients are mixed into their products before the pills are formed, and therefore should be evenly distributed (though they cannot guarantee this). However, both manufacturers advise against pill splitting.”
So maybe not splitting is just a precautionary recommendation. In which case it is unlikely the splitting would have been an issue.
