Randomised controlled trials in single patients

Results of large randomised controlled trials may not help in deciding treatment for an individual patient. This may be because the patient differs clinically from those in the trials, or because wide variations between individuals in a trial limit the applicability of results to an individual patient. In these circumstances, a randomised controlled trial in the individual patient (an n-of-1 trial) may help. This approach may also help when the prescriber or patient doubts whether the treatment is, or will be, beneficial, when the optimal dosage is uncertain, or to assess whether an unwanted effect is due to a particular treatment. Here we discuss the use of this technique.