Flegal KM, Carroll MD, Kit BK, Ogden CL Prevalence of obesity and trends in the distribution of body mass index among US adults, 1999-2010. JAMA. 2012 Feb 1;307(5):491-7. doi: 10.1001/jama.2012.39. Epub 2012 Jan 17.
Graesslin O, Korver T The contraceptive efficacy of Implanon: a review of clinical trials and marketing experience. Eur J Contracept Reprod Health Care. 2008 Jun;13 Suppl 1:4-12. doi: 10.1080/13625180801942754. Review.
Huber J, Wenzl R Pharmacokinetics of Implanon. An integrated analysis. Contraception. 1998 Dec;58(6 Suppl):85S-90S. Erratum in: Contraception 1999 Feb;59(2):145. Retraction in: Rekers H, Affandi B. Contraception. 2004 Nov;70(5):433.
Jacobson JC, Aikins Murphy P United States medical eligibility criteria for contraceptive use 2010: a review of changes. J Midwifery Womens Health. 2011 Nov-Dec;56(6):598-607. doi: 10.1111/j.1542-2011.2011.00093.x. Epub 2011 Oct 17. Review.
Schnabel P, Merki-Feld GS, Malvy A, Duijkers I, Mommers E, van den Heuvel MW Bioequivalence and x-ray visibility of a radiopaque etonogestrel implant versus a non-radiopaque implant: a 3-year, randomized, double-blind study. Clin Drug Investig. 2012 Jun 1;32(6):413-22. doi: 10.2165/11631930-000000000-00000.
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.
