Cytisine for smoking cessation

1
Cytisine for smoking cessation

• A literature review and a meta-analysis
• Jean-François ETTER, PhD
• Institute of social and preventive medicine
• University of Geneva - Switzerland
• E-mail JFE_at_JFE.CH
• August 28, 2006

2
Background

• Cytisine is found in the seeds of the golden rain
  tree (Cytisus laburnum).
• Cytisine (not to be confounded with cytosine) is
  an agonist of nicotinic receptors, it binds
  strongly to alpha4-beta2 nicotinic receptors.
• Varenicline is derived from cytisine.
• Cytisine has been used to treat tobacco
  dependence for 40 years in Eastern Europe.
• Cytisine is sold as a smoking cessation drug by a
  Bulgarian firm under the commercial name of Tabex
• See www.tabex.net

3
Objectives

• To review the literature on the effect of
  cytisine on smoking cessation.
• To conduct a meta-analysis of placebo-controlled
  trials.

4
Data sources

• We reviewed . PubMed, . Embase, .
  Psychological Abstracts, . Biosis, .
  Google.com and Scholar.google.com,
• Using the keywords cytisine, cytisin, zytisin,
  cytisinum, Tabex and smoking cessation, and
• We contacted experts in several countries and the
  producer of Tabex.
• We obtained professional translations of articles
  in Polish, Bulgarian, Russian and German

5
Data synthesis

• We found 10 studies reporting on the effects of
  cytisine on smoking cessation,
• Including 4 controlled studies (3
  placebo-controlled).
• 9 studies used the Bulgarian drug Tabex,
  containing 1.5 mg cytisine per tablet.
• One Russian study used buccal films containing
  either 1.5 mg cytisine or 0.75 mg cytisine plus
  0.75 mg anabasine.
• All studies were published between 1967 and 2005
  in Bulgaria, Germany, Poland and Russia.

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Data synthesis

• There were 4427 smokers treated with cytisine and
  3518 smokers in control conditions.
• The pooled odds ratio after 3-8 weeks in the 3
  placebo-controlled trials (two were doubled-blind
  and one was randomized) was 1.93 (95 CI 1.21 to
  3.06).
• For the 2 placebo-controlled, double-blind trials
  with longer follow-up, the pooled odds ratio
  after 3-6 months was 1.83 (1.12 to 2.99).
• One placebo-controlled, double-blind trial had
  follow-up after 2 years (odds ratio1.77, 1.29 to
  2.43).
• Some side effects were reported.

7
Meta-analysis of the effect of cytisine versus
placebo on smoking cessation at the end of
treatment, after 3-8 weeks
8
Conclusions

• Cytisine is very probably effective for smoking
  cessation.
• Studies of poor methodological quality.
• This fact remained largely unnoticed in the
  English-language literature.
• How many other effective drugs are there, which
  remained unnoticed because efficacy trials were
  never published in English in Western countries?
• Competing interests none
• Funding none
• Paper published as Cytisine for smoking
  cessation a literature review and a
  meta-analysis. Arch Intern Med. 20061661553-9.