Double-Blind Study: Who Does Not Know What | Dose Track
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Double-blind

Also called double-blind study, double-masked, blinded trial, blinding · Reviewed

Definition: A double-blind study is a trial in which neither the people taking part nor the researchers know who is getting which treatment until the trial is over. The NCI says this makes the results less likely to be biased by things that have nothing to do with the treatment.

Why trials are blinded

FDA rules for well-controlled studies (21 CFR 314.126) ask for steps to limit bias by the people in the study, the observers and the analysts of the data, and name blinding as one such step. If people know they are on the real drug, they may report symptoms differently, and a researcher may judge them differently.

Blinded trials on labels

  • AndroGel 1.62%: a 182-day double-blind, placebo-controlled period with 234 men on the gel and 40 on placebo. 25 men on the gel (10.7%) stopped because of side effects, 17 of them for a rise in PSA.
  • Addyi: its side-effect tables come from randomized, double-blind, placebo-controlled trials in women with low sexual desire.
  • Follistim AQ: one of its tables comes from an assessor-blind comparative study, which shows that not every trial blinds both sides.

After its blinded period, the AndroGel trial moved to an open-label period, in which everyone knew they were on the gel.

Why it matters for your log

You always know what you take, so your own notes are never blind. Writing down symptoms on the day they happen, rather than from memory later, keeps the record as plain as it can be.

Read more on Dose Track: AndroGel side effects · Addyi side effects · Follistim AQ side effects · Testim vs AndroGel

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
PlaceboA placebo is an inactive substance or other treatment that looks the same as, and is given the same way… Randomized controlled trialA randomized controlled trial (RCT) is a study that splits people into groups by chance and gives each… Open-labelAn open-label study is one in which both the health providers and the patients know which drug or… Adverse eventAn adverse event is an undesired effect of a drug or other treatment, from mild to life-threatening. The…

Frequently asked questions

What does double-blind mean?+
Neither the people in the trial nor the researchers know who is getting the drug and who is getting the comparison until the trial ends.
Why does blinding matter?+
The NCI says it makes the results less likely to be biased by factors not related to the treatment. FDA rules list blinding as a way to limit bias by participants, observers and analysts.

Sources

  1. NCI Dictionary of Cancer Terms: double-blind study
  2. 21 CFR 314.126: adequate and well-controlled studies, Cornell LII
  3. AndroGel 1.62% (testosterone gel) US prescribing information, DailyMed
  4. Addyi (flibanserin) US prescribing information, DailyMed
  5. Follistim AQ Cartridge (follitropin beta) US prescribing information, DailyMed

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