Clinical Trials

Clinical Trials: A Practical Guide ■❚❙❘as they accrue. Triple blinding is appropriate for studies in which the risk ofadverse events due to the new or standard treatment is low, and should not beused for treatments where safety is a critical issue. Due to the reduced ability ofthe DMSC to see trends early, recruitment might need to continue until statisticalsignificance is reached for either clinical effects or adverse events.Coding of drugsDrug treatments involved in a study are usually known by a code (eg, study drug,identification batch 62, number 29), which is recorded with a unique patientnumber. This code prevents knowledge of whether the drug is the new/standardtreatment or a placebo. Many drugs can still be recognized by specific side-effects,such as flushing of the face or a metallic taste in the mouth. If several participantswith a similar drug code experience the same side-effects then this could unblindthe study. Therefore, unique codes might be needed for each patient, but in largestudies the use of unique codes might not be practical. In emergency situations,for instance when patients or investigators do not have access to their owntreatment, investigators might have to ‘borrow’ medication from anotheridentically coded patient until further stocks arrive.Unblinding studiesAccidental unblinding might occur, for example, when the distribution center failsto remove all of the drug identification packing slips from the cartons, or if a bloodor imaging laboratory mistakenly sends the investigators results for theparticipants sorted by treatment. In emergency situations it might be importantfor the attending investigator to know which treatment the patient is taking, butin most emergencies the medication can be withdrawn without breaking theblinding, or the specific investigator can be informed of the code without theparticipant or principal investigator being informed.Methods for fast and efficient unblinding should be in place with clear guidelinesas to when it is appropriate. For example, each medicine bottle used in the studycould have a tear-off strip that can be kept in the pharmacy and opened in anemergency in order to reveal the identity of the drug. Care should be taken toensure that the label cannot be read through the seal.79