Intended for healthcare professionals

Endgames Statistical Question

Phases of clinical trials

BMJ 2011; 343 doi: (Published 28 September 2011) Cite this as: BMJ 2011;343:d6068
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}

Researchers assessed the efficacy of nortriptyline when combined with nicotine replacement for smoking cessation. A randomised controlled trial was performed. Participants were included if they were trying to stop smoking. In total, 445 participants were randomised to nortriptyline combined with nicotine replacement and 456 to control (placebo plus nicotine replacement). The primary outcome was prolonged confirmed abstinence at six months.1

Nortriptyline is an antidepressant, and although at the time of the study it was not licensed for smoking cessation, it had shown benefit in previous trials. Nicotine replacement is licensed for smoking cessation and is the most commonly used drug in this setting.

The proportion of people who achieved prolonged abstinence at six months was greater in those using nortriptyline than in those using placebo, although the difference was not statistically significant (16% v 12%; relative risk 1.34, 95% confidence interval 0.97 to 1.86). The authors concluded that although nortriptyline and nicotine replacement are effective drugs in smoking cessation, combined treatment is no more effective than either treatment alone.

Which one of the following options best describes the phase of the above clinical trial?

  • a) Phase I

  • b) Phase II

  • c) Phase III

  • d) Phase …

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