"Monthly preventatives" refers to medications or treatments that are given or applied to prevent or protect against certain health issues every month. Full definition
Cats that live in colder areas, where mosquitoes are seasonal, should be on monthly preventative for at least 6 months of the year. (michigananimalhospital.com)
If you are a prospective dog owner and you can not afford to administer monthly preventative medications, you should reconsider your desire for a dog. (caninejournal.com)
We will most likely never be able to entirely eliminate heartworm, so monthly preventative treatments are important year - round. (vetbabble.com)