Thanks!! That makes sense! I wonder if it’s different for cats? Or even she even needs it? She does go outside so I’m sure she does.They tell you not to give heartworm meds until the dog is tested for heartworms. From what I've read, this isn't necessary except with the old meds no longer used. You can just give the HW meds now--not that you wouldn't want to know, but it isn't dangerous except to certain breeds (as you already knew).
Did I post my link to this thread? I started to... Anyway, here it is: http://www.dogaware.com/health/ivomec.html#08sheepdrench