Can a 13-year-old dog start taking heartworm medication for the first time?

Our question this week was:

Can a 13-year-old bichon frise, who just moved here from Sweden, take heartworm pills (Sentinel or something similar) along with levothyroxine and trilostan (for Cushing's Syndrome)?

His owner does not speak English well and asked me to find out for her. Heartworm is not an issue in Sweden so he has never taken any medication to prevent it. There is a concern now that he needs to take it, and she has no access to a veterinarian until she gets settled.

Patricia Jensen.


Hi Patricia– thanks for your email and contacting me on your friend's behalf. To answer your question, yes, a 13-year-old dog can take heartworm prevention medication along with the other medications that you mentioned.

If your friend lives in an area endemic for heartworm, it is a good idea. I'd recommend that the dog be blood tested to ensure that he is heartworm negative first, then starting on the preventive medication.

An article that might be helpful to you is Heartworm Prevention Guidelines for Dogs.

Best of luck!

Dr. Debra

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