@TwiLyghtSansSparkles Although I don't have any personal experience with Frontline for dogs, I've found it to be pretty effective for my cats. (They have different formulas for cats and dogs, I believe.)
And if other pet owners are saying the medication the vet recommended is ineffective or worse, harmful, I'd say you're absolutely right to be looking for alternatives. Strangely enough, vets don't always tell you the best thing for your pet.
And now I'm going to go on a bit of a rant about feline diabetes.
Because most inexpensive types of cat food are dry kibble type stuff, where the main ingredients are wheat, corn, or other grains, house cats can get Type II diabetes since they are carnivores and therefore not equipped to process all those carbs. When we discovered that our cat Tiger was diabetic, the vet recommended a diet of specialized high-fiber dry cat food. But my mom did some research on her own and decided to start feeding him a low-carb diet of wet cat food made mostly from real meat. Simply by changing his food, we were able to lower Tiger's blood sugar from over 400 (dangerously high) to slightly under 200 (still high, but not life-threateningly so).
To get his blood glucose the rest of the way into the healthy range, we started giving Tiger insulin shots after meals just like you would for a diabetic person. So during a lot of my high school career, I would come home after school, feed Tiger, test his sugar, and then inject him with an appropriate amount of insulin.
The vet did not like this. She told us we should be giving Tiger the same amount of insulin 4x a day without bothering to test his sugar. In reality, that's a great way to send your kitty into a hypoglycemic coma or even kill him. If you're giving him more insulin than his current blood sugar warrants (and it's impossible to know without a glucose test immediately beforehand), then it'll get dangerously low and he'll crash. And in fact, the same thing can happen with diabetic people who take medications like Metformin to lower their blood sugar if they don't pay careful attention to how the medication affects them personally, since it doesn't work exactly the same for everyone. My grandpa knows a guy whose wife actually DIED from taking too high a dose of Metformin because the doctor was adamant that she needed to take that much.
So yeah. Don't necessarily take the vet's word for it just because they're the vet.