Evening Primrose Oil for Atopic Dermatitis
Interest was fuelled because evening primrose oil extract
(containing 8-10% of gamma linolenic acid (GLA)) appeared to cause few side
effects and because there was a very plausible mechanism to explain why
supplementation with this essential fatty acid might work in atopic dermatitis.
Since then many studies have evaluated the efficacy of oral gamma linolenic
acid supplementation for atopic dermatitis, with conflicting results. Fifteen
studies (10 dealing with evening primrose oil, and five with borage oil,
which contains even higher concentrations of GLA) were summarised in a
systematic review of atopic dermatitis treatments that I and others
conducted for the NHS Health Technology Assessment programmes. Medicines
Control Agency’s decision to withdraw the product licence, suggests that GLA
supplementation for atopic dermatitis has had its day.
Yet many questions surrounding the story of evening primrose oil for
eczema remain unanswered:
Unanswered questions
In 1989 Horrobin et al published a meta-analysis in the British Journal of
Dermatology of the two earliest studies plus another seven small (14-47
participants) company sponsored studies of evening primrose oil (Epogam,
Scotia Pharmaceuticals) for atopic dermatitis. They found that atopic
dermatitis improvement scores for evening primrose oil were
significantly better
seven company trials included in that study have never since appeared in
the public domain, the other concern about that meta-analysis was its exclusion
of the one other independent and relatively large study (123 participants) by
Bamford .
The company authors of the meta-analysis suggested that active versus
placebo treatments became mixed up in the Bamford study, based on an analysis
done by the company of fatty acid levels in blood samples taken from study
participants. After this meta-analysis was published,
others thought it odd that Bamford et al never published a response to the
company’s serious
criticisms of their study.10 In fact Bamford immediately wrote a lengthy
and clear explanation of the steps that were in place to avoid such purported
contamination, but he was refused an opportunity to defend his study with a
published response because the journal decided that Bamford’s response did not
add anything to the understanding on the use of evening primrose oil as
a supplemental treatment for atopic eczema (J Bamford, written communication 12
Nov 2003).
A year later, two British dermatologists wrote a detailed review article on
evening primrose oil and atopic dermatitis. 27 November 2003).
Too little data in the public domain
The Health Technology Assessment systematic review published in 2000
provided an opportunity for the company to hand over its unpublished studies
for inclusion in that report.5 Although Searle wrote back to tell us that they
would be “compiling the data,” no data have
been forthcoming to date.We can only hope that it will be compiled in time
for the current Cochrane review on GLA supplementation for atopic dermatitis. Finally,
in the autumn of 2002 the Medicines Control Agency withdrew the marketing
authorisations for evening primrose oil following a “review of all the
relevant information, including new studies,” although which information and
new studies is unclear from the very limited information available on the
agency’s website.
In fairness to the innovators of evening primrose oil for atopic
dermatitis, they evaluated their product more than many other products used in
dermatology. Nobody would have been happier than myself if evening primrose
oil had produced a clinically worthwhile benefit for eczema sufferers. But
the history of its development has been marred by lack of data in the public
domain. As we bid goodnight to the evening primrose oil story, perhaps we can
awaken to a world where all clinical trial data, derived from people who are
good enough to volunteer for such studies, reach the light of day, where they
can be openly debated in the public domain
