Multiple n = 1 trials in the identification of responders and non-responders to the cognitive effects of Ginkgo biloba.
OBJECTIVE
A pilot study to assess multiple crossover n = 1 trials with verum/placebo discrimination as the outcome measure as a means of identifying responders and non-responders to the acute nootropic effect of Ginkgo biloba (G. biloba) among healthy volunteers.


METHODS
Multiple double-blind, placebo-controlled n = 1 trials with 8 treatments in randomized order and separated by minimum washout periods of 7 days. Treatments were acute 120 mg doses of G. biloba extract (GK501) or undistinguishable placebo. The frequency distribution of correct scores for verum-placebo discrimination was compared with the binomial distribution to identify putative responders, who were then tested for consistency of performance over a further 8 treatments.


RESULTS
The frequency distribution of scores (n = 11) was bimodal and a discontinuity defined 3 putative responders and 2 putative negative responders for re-test. Two of the putative responders again performed at above chance level and the probability of achieving their scores or better by chance was 0.013 and 0.052.


CONCLUSIONS
n = 1 trials with verum/placebo discrimination as outcome are a promising method for exploring response heterogeneity to treatments with a subjective effect. Preliminary evidence suggests that there are responders and non-responders to an acute G. biloba treatment among healthy subjects.
Canter
P H
PH
Complementary Medicine, Peninsula Medical School, Universities of Exeter and Plymouth, Exeter, Devon, UK. peter.canter@pms.ac.uk
Ernst
E
E
D000328:Adult; D003072:Cognition Disorders / Q000188:drug therapy*; D004192:Discrimination, Psychological; D004311:Double-Blind Method; D005260:Female; D005794:Generalization, Response / Q000502:physiology; D020441:Ginkgo biloba; D006801:Humans; D008297:Male; D008875:Middle Aged; D008517:Phytotherapy; D010865:Pilot Projects; D010936:Plant Extracts / Q000008:administration & dosage* / Q000009:adverse effects; D013607:Tablets; D013997:Time Factors; D000096983:Ginkgo Extract
D010936:Plant Extracts; D013607:Tablets; C114787:Ginkgo biloba extract 501; D000096983:Ginkgo Extract