Order to replace some birth control pills other you cannot, even in case of occurrence of side effects. Consult to the doctor and discuss with him the causes and the methods of transition to another contraceptive.
In any case, do not stop taking the pills, without finishing his course to the end. This can lead to disruption of the menstrual cycle, pregnancy and the discovery of uterine bleeding. Finish your drink hormonal tablets before the end of the package and only then move on to another drug or just cancel the appointment. The only exception is pregnancy. If you're diagnosing this fact immediately stop taking contraceptives.
If you want to get pregnant and took pills to protect, you can opt out of receiving them at any time, even after packaging. But in this case, most likely, will appear spotting that will remind menstruation. Only they will be less abundant and more lasting. Typically such allocation is not more than 2 weeks.
To change birth control pills, consisting of 21 pieces pack, drink the last pill and wait 7 days, then start taking new drugs. If in packing 28 tablets, wait 7 days is not necessary. The last drink and the next day start taking new contraceptives. In the same way you can switch from birth control pills to other types of contraception.
If you successfully make the transition from one contraceptive to the other, the risk of unwanted pregnancies will be minimal.
There are cases when the change of hormone pills accompanied by side effects: spotting vaginal discharge, nausea, headaches. Usually these symptoms pass quickly and do not require discontinuation of contraceptives.