Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
When these two medicines are taken together, the tetracycline medicine may alter the way your body processes the birth control pill.
What might happen:
The effects of your birth control pills may decrease and cause breakthrough bleeding, spotting, or even an unintended pregnancy.
What you should do about this interaction:
General consensus is that a backup method of birth control is not needed while taking this antibiotic. If you have questions or concerns, discuss them with your healthcare professional (e.g. doctor or pharmacist).Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Bacon JF, Shenfield GM. Pregnancy attributable to interaction between tetracycline and oral contraceptives. Br Med J 1980 Feb 2;280(6210):293.
2.Murphy AA, Zacur HA, Charache P, Burkman RT. The effect of tetracycline on levels of oral contraceptives. Am J Obstet Gynecol 1991 Jan;164(1 Pt 1):28-33.
3.Neely JL, Abate M, Swinker M, D'Angio R. The effect of doxycycline on serum levels of ethinyl estradiol, norethindrone, and endogenous progesterone. Obstet Gynecol 1991 Mar;77(3):416-20.
4.Faculty of Sexual and Reproductive Healthcare Clinical Effectiveness Unit. Clinical guidance drug interactions with hormonal contraception. January, 2011.
5.Centers for Disease Control and Prevention. U.S. Medical Eligibility Criteria for Contraceptive Use, 2010. MMWR Early Release 2010;59:1-86.