Digitalis Investigation Group The effect of digoxin on mortality and morbidity in patients with heart failure. N Engl J Med. 1997 Feb 20;336(8):525-33.
Gheorghiade M, Pitt B Digitalis Investigation Group (DIG) trial: a stimulus for further research. Am Heart J. 1997 Jul;134(1):3-12. Review.
Hobbs RE Digoxin's effect on mortality and hospitalization in heart failure: implications of the DIG study. Digitalis Investigation Group. Cleve Clin J Med. 1997 May;64(5):234-7.
Jones RC, Francis GS, Lauer MS Predictors of mortality in patients with heart failure and preserved systolic function in the Digitalis Investigation Group trial. J Am Coll Cardiol. 2004 Sep 1;44(5):1025-9.
Rathore SS, Wang Y, Krumholz HM Sex-based differences in the effect of digoxin for the treatment of heart failure. N Engl J Med. 2002 Oct 31;347(18):1403-11.
Interventional studies are often prospective and are specifically tailored to evaluate direct impacts of treatment or preventive measures on disease.
Observational studies are often retrospective and are used to assess potential causation in exposure-outcome relationships and therefore influence preventive methods.
Expanded access is a means by which manufacturers make investigational new drugs available, under certain circumstances, to treat a patient(s) with a serious disease or condition who cannot participate in a controlled clinical trial.
Clinical trials are conducted in a series of steps, called phases - each phase is designed to answer a separate research question.
Phase 1: Researchers test a new drug or treatment in a small group of people for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.
Phase 2: The drug or treatment is given to a larger group of people to see if it is effective and to further evaluate its safety.
Phase 3: The drug or treatment is given to large groups of people to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug or treatment to be used safely.
Phase 4: Studies are done after the drug or treatment has been marketed to gather information on the drug's effect in various populations and any side effects associated with long-term use.
