Kariva is a birth control pill with a shortened placebo interval--2 days vs. the regular 7 days.
I mentioned before that some combination birth control pill brands have a shortened placebo interval.
Using a brand like Kariva helps if you suffer from problems related to your period or withdrawal bleeding episode (the fake period) like painful periods, migraines, endometriosis, etc. If you recall, these problems tend to be caused/exacerbated by hormone fluctuations.
If you're on the Pill, you have less hormone fluctuations than a nonuser, at least for 3 weeks out of the month (the 3 weeks with active, hormone pills). Unfortunately, during the hormone-free week (the 7 days with placebo pills) the hormone levels start to fluctuate again, and the problems recur. So, shortening the placebo interval, for example, from 7 to 2 days, helps. But wait, there's more! [Obviously, I'm watching too much late-night TV.]
Another advantage of using a brand with a shortened placebo interval is better "real life" pregnancy protection. In real life, it's common for women to miss the first few pill days of a new pack, because they aren't able to get the new pack in time. Coming off of a placebo week, this is quite risky. Why? Because there's a danger of a mature egg being released from the ovary. [Mature egg + sperm = possible bebe.] So, after a placebo week, the more days you miss before starting a new pack, the higher your risk of an unintended pregnancy. Ideally, all combination Pill brands should be packaged with 21 days of active pills and only 2-3 days of placebo pills. This way, even if something happens and you are unable to start a new pack right away, you are still protected.
In the U.S., there is only one type of biphasic Pill with a shortened placebo interval: an estrogen (ethinyl estradiol or EE)/progestin (desogestrel or D) combination. The dosage is 21 days of 0.02 mg EE/0.15 mg D, 2 days of placebo, followed by 5 days of 0.01 mg EE. Because this type of Pill can be very useful for many women, I wanted to alert you to some [confusing] changes in the brand names.
Initially, there was Mircette, manufactured by Organon. Then Barr came up with a generic, Kariva. Now, Organon is no longer manufacturing Mircette, however they are allowing another pharma company, Prasco, to market a generic versions of Mircette (don't know the name for this version yet; it's supposed to be available next year). So, if you're interested in using a brand with a shortened interval, ask for Kariva, not Mircette.
ETA: Mircette is now registered to Duramed Pharmaceuticals, Inc., a subsidiary of Barr.