Patient is a 9 year old 49 lb. Australian Shepherd
Client: I picked up some Sentinel today. As you were out of the under 50 lb. packs your vet tech said since my dog was 49lbs I could give her the 51-100 lb. tablet. Can I cut this tablet in half and give it to her? It would double my supply 
Dr. Dalo: It is actually better to give her 1 tablet of the 51-100 lb. medication once a month since as she ages many dogs outgrow the lower dose pills. Both the medications in Sentinel (heartworm and flea prevention) are extremely safe and cutting them in half will not give her the consistent monthly dose needed. When a dog is this close to 50 lbs I recommend using the next higher dose that way if she gains 2 lbs in the next 6 months you would need the higher dose. Also, once you take the tab out of the blister wrap the company says the drug becomes less effective when stored out of this sealed blister wrap for 30 days. This is another reason we don’t recommend clients to cut these pills. But if this (giving the higher dose medication) makes you uncomfortable for any reason I am sure we will have the next dose down boxes within a few days. If you go that way, I would monitor her weight on a monthly basis to make sure you are giving enough.