Study author Dr. Lianne Parkin and colleagues from the Dunedin School of Medicine,
University of Otago, New Zealand, and analyzed women aged 15 to 44 years
without major risk factors for venous thromboembolism, who started using an
oral contraceptive pill containing oestrogen 30 microgm plus either
levonorgestrel or drospirenone between May 2002 and September 2009.
observed that the use of drospirenone contraceptive was associated with a three fold higher risk of non-fatal
idiopathic venous thromboembolism (VTE) as compared to levonorgestrel use.
The odds ratio, adjusted for body mass index, was 3.3. Sub analyses further
suggested that referral, first time user, diagnostic, duration of use, and
switching biases were unlikely explanations for this finding.
Parkin commented saying, "These findings
support more recent studies that suggest that drospirenone oral contraceptives
are not as safe as levonorgestrel oral contraceptives with respect to venous
thromboembolism and, in the absence of other considerations, should not be the
first choice in oral contraception."
concluded by saying that their findings "Add to emerging evidence that use of
the oral contraceptive containing drospirenone is associated with a higher risk
of VTE than are preparations containing levonorgestrel."