The common consensus is that it takes about 40‒50 days for heartworm larvae to mature to the point where heartworm preventatives no longer work. So, from the initial mosquito bite to the beginning of maturation, there is an approximate 45-day grace period that a heartworm preventative can provide protection.
Can you use expired Heartgard?
It isn't safe to use expired heartworm medication or any other type of expired medication for dogs. The insecticide used to kill heartworms--in many cases, milbemycin oxime--might not be effective after the expiration date.
What is the shelf life of Heartgard?
Heartgard Plus does seem to have a long shelf life of 1-2 years. It comes in very convenient dosing package sizes of up to 25 pound dogs, 26 to 50 pound packaging/dosing, and 51-100 pound packaging and dosing.
Does heartworm medication expire?
The expiration date on my pet's heartworm medication is past. Can I still use the medication? As with all drugs or pharmaceutical products, heartworm preventives should be used before the expiration date on the package, because it is impossible to predict if it will be effective or safe.
Can you use expired dog medicine?
Yes and no. If a medication is past the expiration date determined by the manufacturer, it is best not to use it. While it may not directly cause harm, using an expired drug may have some negative effects including: Delay in appropriate treatment.
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