Combined antithrombotics associated with high GI risks
Treatment with more than one antithrombotic agent is increasing and
is associated with a high incidence of gastrointestinal bleeding, according
to the authors of a paper published
online on 19 September (BMJ
Online First).
The researchers conducted a case control study of 1,443 cases of serious
upper gastro-intestinal bleeding and 57,720 matched controls. The main
outcome measurement was exposure to low-dose aspirin, clopidogrel, dipyridamole,
vitamin K antagonists and combined antithrombotic treatment.
The results showed a dramatic increase in the use of combined antithrombotic
drugs between 1995 and 2004. The total exposure to combined regimens
was 758 person years in 2000 and 3,978 person years in 2004.
Analysis of the data showed consistently higher odds ratios for combinations
than for single drug regimens. For example, the researchers calculated
that there would be one excess bleeding case per 124 treatment years
in patients taking a combination of clopidogrel and aspirin, compared
with one per 1,040 treatment years for those taking aspirin alone and
one per 8,800 treatment years for clopidogrel alone.
“The decision to treat a patient with an aggressive antithrombotic
regimen ultimately relies on the balancing of benefits and risks. Although
we
included a sizeable number of cases, we had too few to identify subgroups
with particularly high or low risk. Future studies with higher power
might aid individualising treatment,” they conclude. |
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