Clinical trials are a key research tool for advancing medical knowledge and patient care. Clinical research is done only if doctors don’t know

  • whether a new approach works well in people and is safe and
  • which treatments or strategies work best for certain illnesses or groups of people.

Some clinical trials show a positive result. For example, the National Heart, Lung, and Blood Institute (NHLBI) sponsored a trial of two different combinations of asthma treatments. The trial found that one of the combinations worked much better than the other for moderate persistent asthma. The results provided important treatment information for doctors and patients.

The results from other clinical trials show what doesn’t work or may cause harm. For example, the NHLBI Women’s Health Initiative tested whether hormone therapy (HT) reduced the risk of heart disease in postmenopausal women. (When the trial began, HT was already in common use for the treatment of menopausal symptoms. It also was increasingly being used for prevention of heart disease.)

The study found that HT increased the risk of heart disease in the first few years, and HT also increased the risk of stroke and blood clots. In women who took a combination of estrogen and progestin, the risk of breast cancer also increased.

As a result, the U.S. Food and Drug Administration now recommends never using HT to prevent heart disease. When HT is used for menopausal symptoms, it should be taken only at the smallest dose and for the shortest time possible.

Clinical trials, like the two described above, help improve and advance medical care. They also can help health care decisionmakers direct resources to the strategies and treatments that work best

Phases of Clinical Research

Phase 1
Phase 1 studies involve testing normal patients with the new medication to show safety of the medication at various doses.

Phase 2
Phase 2 studies involve using the medication in patients with a specific disease to determine side-effects and doses needed.

Phase 3
Phase 3 studies are larger clinical trials involving hundreds to thousands of patients to further show the effectiveness and safety of the medication

Phase 4

Phase 4 studies involve further research of FDA approved treatments, these trials are often focused on gathering new information on effectiveness.