Weak link between SSRIs and abnormal bleeding
PATIENTS prescribed selective serotonin reuptake inhibitors
(SSRIs) may show an increased, but not significant tendency towards abnormal
bleeding, suggest researchers from the Drug Safety Research Unit, Southampton
University.
The researchers, led by Dr Saad Shakir, say that
the study provides weak evidence to support a link between SSRIs and precipitation
of abnormal bleeding. Based on prescription-event monitoring in England,
the study examined bleeding events reported for 50,150 patients prescribed
one of four SSRIs — fluoxetine, paroxetine, fluvoxamine or sertraline.
The rate of bleeding events was compared with events reported for patients
taking either non-SSRI agents prescribed for psychiatric disorders or
a range of non-psychiatric drugs. No significant differences in bleeding
events were identified between the groups but there was a tendency towards
the highest risk with the SSRI group and the lowest risk with the control
groups, they say.
Speaking to The Journal on 10 July, Dr Shakir
said that the study presented a new analysis of the data that had been
generated over six months following the launch of each product on to the
United Kingdom market. The analysis was conducted in response to reports
and anecdotal evidence pointing to a link between SSRIs and abnormal bleeding,
he said. Clinical practice need not change, but the balance of evidence
indicated caution when using SSRIs in circumstances where bleeding might
be potentiated, suggested Dr Shakir.
Commenting on the findings, representatives of GlaxoSmithKline
(manufacturer of paroxetine, Seroxat), Pfizer (sertraline, Lustral) and
Solvay Healthcare (fluvoxamine, Faverin) say that the summary of product
characteristics for their SSRIs already carry a reference to the potential
association between abnormal bleeding and SSRI use. The SPCs recommend
that caution be advised for patients taking SSRIs concomitantly with drugs
affecting platelet function as well as for patients with a history of
bleeding disorders.
With regard to a pharmacological basis for an increased
risk in bleeding, the researchers comment that over 90 per cent of circulating
serotonin is contained in platelets. Serotonin is released during platelet
activation and amplifies the aggregation response through activation of
5HT2A receptors, they say (Eur J Clin Pharmacol 2001;52:167–76).
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