What determines over-the-counter drugs versus prescription ones?

Safety profile: Many medications are introduced after years of research & those found safe & effective are initially approved by the fda for prescription use.Initial use is monitored for drug reactions. In time the manufacturer can petition for open non-prescription use. Otc approval sometimes comes with conditions such as limiting the dose size & requiring extra safety labeling.

No prescription need: Otc drugs - the ones when no prescription needed to buy them at the pharmacy. It is usually vitamins, anti-inflammatory, cold medication, anti-allergic, herbal, etc. They won't cause significant side effects, but may cause an interaction with the prescribed drugs.