Oral contraceptive and drugs interactions

Hi Doc,

My girlfriend has been in a panic lately about her contraceptive pill (mercilon). Previously she has always had a bar in her arm but switched 2 months ago to the pill. Do any of the following affect how well the pill works: Mephedrone, methylone, cocaine, mdma, alcohol or in any combination of the above?

Originally posted in SR 2.0 7/4/14 . Reviewed 8/2/23

There are no  significant pharmacological interactions between common  drugs and birth control pills. The use of substances you mention does not alter efficacy of birth control pills. Neither any other hormone-based method: patches, transdermal implants, vaginal rings …

Equally important, contraceptive efficacy of the «morning-after pill» is also not affected

There are some studies that suggest  pharmacological interactions between cannabinoids and some contraceptives . But these are experiments «in vitro» and do not seem to have any practical relevance in humans.

And the same goes for combinations. We will consider «combination» the use of moderate doses and reasonable frequencies of a few substances. «Drug salads» ( taking whatever anyone offers to you without  criteria) often have unpredictable effects, regardless of the use of contraceptives or any other medication.

In relation to drugs and hormonal contraceptives, one important exception is tobacco. Women who smoke tobacco are at increased risk of certain adverse effects.  Smoking increases hormone levels in the blood, which can lead to an increased risk of blood clots, myocardial infarction and stroke.

In addition, smoking is associated with a decrease in good (HDL) cholesterol levels and an increase in bad (LDL) cholesterol levels. This contributes also to cardiovascular problems.

It is therefore recommended that women using oral contraceptives do not smoke (especially women over 35 years of age). If a woman is unwilling or unable to quit smoking, it is reasonable to consider another method of contraception.

Like many other drugs, oral contraceptives are used on a daily basis.So, it is important not to forget doses in order to maintain their effectiveness. This can be significant in the context of a rave or party lasting several days. In any case, weekly or monthly contraceptives are available for people who have a tendency to forget to take a drug every day.