What makes the Contraceptive Pill Less Effective?


Combined Contraceptive Pill »

Although the contraceptive pill is very effective at preventing pregnancy, you should be aware that there are a number of factors that can make the pill less effective, especially certain types of medications.

What many people do not realize is that antibiotics can stop the pill from protecting you from pregnancy. The main two antibiotics that do this are rifabutin and Rifampicin. If you are using these antibiotics then you must use extra protection, as there is a greater chance you could become pregnant. If you are going to be prescribed either of these antibiotics in the long term, then you should talk to your doctor about switching to a different form of contraception that is not affected by these antibiotics such as the inauterine device.

Another class of medication that alters the effect of the pill is anti epileptic drugs. These include carbamazpine, Phenytoin, topirarnate, Phenobarbital, primidone or oxarbozapine. If you are on these medications, you will be told to consider other forms of contraception.  Also some antiviral HIV medications will make the pill less effective.

A herbal remedy called St Johns wort also affects the effectiveness of the pill. It is an herbal plant that is used by some people to treat depression.  However, it can decrease your protection from pregnancy.

If you experience vomiting or diarrhoea, there is a chance that the effectiveness of the pill has been reduced especially if it happens two hours after taking the pill. The hormones in the pill have to absorb into the blood stream and as the pill is taken orally, there is a chance that you will disrupt it before it has the chance to become fully absorbed. If this affects you, take another pill immediately and then continue as normal, taking the next pill at the correct time. This should protect you from pregnancy. However, if you continue to throw up or you have diarrhoea for more than twenty-four hours, there is a good chance that you will not be protected from pregnancy.

Taking the contraceptive pill is your responsibility; therefore if you forget to take it then you will make this form of contraception a lot less effective.  If you forgot just one pill, then you should still be protected but if you forgot to take two or more pills and have done so at near the end of the pack., you will not be protected from pregnancy. However, it also depends on the type of contraceptive pill you are on as to whether you will be protected if you miss a pill. Also, if you take the morning after pill called Elleone, it may interfere with the pill and reduce its protection against pregnancy.


« How to take the Contraceptive Pill Forgetting to take the Contraceptive Pill »