In many studies, some participants receive the new drug, and
other participants receive a placebo. A placebo looks just like
the drug, but is an inactive substance. A double blind clinical
study is when neither researcher nor participant knows who is
getting placebo and who is getting the drug. A single blind
study is when participants do not know whether they are getting
placebo or drug, but the study team does know. Study
participants who receive either standard procedure for the
illness or placebo (no medicine) as compared to study
participants who are receiving a new drug, medical device,
procedure, or prevention. If researchers show that a drug has
'efficacy' (or is 'efficacious'), they show that it improves a
disease or condition in a controlled environment, like a
laboratory. Proving efficacy is a first step to show that the
drug can work when it is taken in the right way. If researchers
show that a drug is 'effective', they show that it improves a
disease or condition outside of a controlled environme