The Drospirenone progesterone only pill ("POP" or “mini pill”) is recommended for women who are unable to use oestrogen containing pills - such as women who suffer with migraine with aura, have a history of thrombosis, or women who smoke and are overweight.
The drospirenone progesterone only pill (Slinda) works in a different way to the older levonorgestrel or norethisterone progesterone-only-pills, and usually gives a more acceptable bleeding pattern.
It works in a similar way to the combined oral contraceptive pill by suppressing ovulation, thinning the uterus lining and thickening the cervical mucous.
Slinda has a contraceptive efficacy of 99% (if used 'perfectly'), and approx 91% with typical pill use. The really positive thing about this pill is that there's more room for timing error - ie, You've got a window of 24 hours to catch up on a missed pill instead of 3 hours!