Is it ok to give my dogs flea & heartworm meds on the same day?

My 2 dogs take Iverhart (generic Heartgard) for heartworm and Comfortis to prevent fleas. Comfortis is a prescription only pill, not a topical. I was just wondering if it is ok to give both meds on the same day. That would make it a lot easier for me to remember and make sure they get both every month. But if... show more My 2 dogs take Iverhart (generic Heartgard) for heartworm and Comfortis to prevent fleas. Comfortis is a prescription only pill, not a topical. I was just wondering if it is ok to give both meds on the same day. That would make it a lot easier for me to remember and make sure they get both every month. But if it could cause interactions or stomach upset I'd want to avoid that.
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