If drugs are tested so carefully during the clinical trials phase, why do we need to monitor them so closely after they receive FDA approval?

No drug is 100% safe and effective for all patients. Every drug, whether it is over-the-counter or prescription, carries some risks, or potential side effects, and sometimes these side effects don’t become known until after the medicine has been made available to the general patient population. Therefore, manufacturers and FDA collaborate on long-term follow-up studies and physicians, nurses, and patients are urged to report any unusual side effect experienced while taking medication.