Yes, there are thrush (yeast infection) treatments available by prescription. Sometimes the over-the-counter stuff doesn't work and you need something stronger. There are also prescription anti-fungal pills that work, too, but they have more side-effects. Call your doctor and ask for a prescription.
Have you been treated before and it keeps coming back? It could be that the stuff you've used hasn't fully killed the yeast. It could also be a bacterial infection, which you cannot treat with over-the-counter treatments. You need a prescription for that.
If you have been treated and just keep getting infections, you need to make sure you are practicing good vaginal health.
1. Wear 100% cotton undies (even go without sometimes, like when you're sleeping)--the vagina needs to breathe
2. Don't douche (it messes with the natural balance)
3. Don't clean the area with harsh soaps or anything (only mild, unscented soap, gently)
4. Don't use scented deodorants, powders, or feminine products (even on pads and tampons)
5. Always wipe front-to-back after using the bathroom
6. If you use lubricants during sex, make sure they're water-based
7. Eat yogurt (good bacteria in your system can prevent bad bacteria and fungus from growing)
8. Don't wear moist clothing for extended periods of time, like after swimming or exercising.
9. If you have unprotected sex, it might be good to have your partner treated, too. Rarely, men can contract yeast infections and without treatment, they can re-infect their partner.
If you follow these steps and still get infections, make sure you go to the doctor and get yourself checked for other possible problems that may make you more vulnerable to infection, like diabetes.