Not known to many people who are taking on birth control methods or procedures, antibiotics can have an effect to the birth control therapy they are currently using. Depending on the type of the antibiotic used, it can have a synergistic or an antagonistic effect over your birth control method of choice.

Generally how long do antibiotics affect birth control? Before we can answer the question, “How long do antibiotics affect birth control?” we first have to discuss the main division of antibiotics that affect birth control.

The two divisions are the synergistic and the antagonistic. Simply put, synergistic antibiotics are antibiotic that make the effects your birth control method longer. Let's take birth control pills. Birth control pills are usually effective for 20 to 28 days and after that you have to take another pill so as to maintain its effect.

What the synergistic type of antibiotic does is that it extends this time frame. So instead of 28 days, the effect can last up to 40 days.

Now you may think that this is very good news since the effect of the birth control method is prolonged but actually it does not bode well to the mechanism happening inside your body. Prolonged effects of birth control methods can damage the cells and some are even shown to cause specific types of cancer.

Antibiotics considered belonging to the synergistic division are your penicillins and penicillin derivatives and monosodium glutamate antibiotics.

The other division the antagonistic effect is equally harmful and equally causes inconvenience. What it does is the opposite of the synergistic antibiotics - they shorten the usual time frame of the effect of your birth control methods.

Taking again the birth control pills as an example, instead of lasting for 20 to 20 days, antagonistic antibiotics can shorten it to 15 even up to 7 days. And that does not bode well as well because the woman may get pregnant even though she is taking the necessary birth control methods.

Some of the drugs belonging to this classification are the propanolol type of antibiotics and the cephazolin line of antibiotics.

Be sure to consult first your doctor before taking any drugs while on birth control.