How Often Are Heartworm Drugs Required?

James Glover
by James Glover
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QuestionMy schnoodle is one years old and I need to know how often I should be giving him heartworm pills. (Nikki Waldie - Colorado)


This depends on what type of heartworm pills you choose to give him. I recommend that even with over-the-counter products you ask your vet before administering medication, since only he will know your pet's full medical history. The most common heartworm preventatives are Macrocyclic Lactones. These are normally administered as a pill on a monthly basis (although topical applications are available). The main types of oral ML available are Ivermectin (eg Heartgard?, Iverhart Plus) and Milbemycin (e.g. Interceptor,Sentinel). These drugs are parasiticides, and will prevent (and treat) heartworm infestation. There are also daily treatments such as Diethylcarbamazine but these tend to be less popular.

Disclaimer: This service is meant to provide advice only and is not meant to replace an appointment with a registered veterinarian. Users should always seek a second opinion. Unfortunately we are only able to answer several questions per week so not everyone gets a published answer. And, unfortunately we can't answer by email.
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Junior Member
Added on July 25th, 2011
I have started my puppy on Heartgard plus for 0 to 25 lbs. I have a couple of 26 to 50 lb. doses left from my last dog.
Is it safe to give one or part of one of these to my puppy next time?