By authorising the use of experimental drugs in the fight against the deadly Ebola virus, the World Health Organisation is allowing a shortcut in drug-vetting procedures that usually take years.
According to the French National Agency for Medicines and Health Products Safety (ANSM), it can take 10 to 15 years from when a drug is first tested in a laboratory to it reaching the market.
After preliminary tests on animals or cells in petri dishes, a laboratory must obtain permission from health authorities for clinical trials on humans to assess a drug's safety and effectiveness.
-- Phase one is generally carried out with a sample of fewer than 100 volunteers to assess drug tolerance and check for side-effects.
-- Phase two evaluates the effectiveness of the drug and the optimal dosage, usually on a sample of several hundred people.
-- Phase three compares the treatment either to a dummy drug (placebo) or a reference drug already commercially available, usually with several thousand people. The aim is to confirm a drug's effectiveness, and assess the ratio of effectiveness to tolerance.
After these clinical trials, which can last between five and 10 years, the laboratory applies to a medicines watchdog to bring the drug to market. In Europe, this is the European Medicines Agency (EMA), and in the United States the Food and Drug Administration (FDA).
For approval, a new treatment must demonstrate a benefit/risk ratio that is equivalent to or better than any existing products.
In cases where no alternative treatment exists, like with Ebola, medicine authorities can allow an acceleration of the procedure on "compassionate grounds."
After a drug has gone to market, it remains under surveillance with an ongoing assessment of any side effects.
If there are any health risks, it can be taken off the shelves at any time.