Survey of pharmacists and physicians on drug interactions between combined oral contraceptives and broad-spectrum antibiotics

OBJECTIVE To evaluate physician and pharmacist knowledge on potential drug interactions between combined oral contraceptives (COC) and broad-spectrum antibiotics and determine if any difference exists between responses. METHODS Two hundred licensed retail pharmacists and 200 licensed family practice physicians in the states of Virginia, West Virginia, and Maryland were mailed an anonymous survey between August 2007 and November 2007. The survey consisted of 3 short questions asking practitioners about their current opinion on drug interactions with COCs and whether an alternative form of contraception is needed for patients taking COC and concomitant broad-spectrum antibiotics. The main outcome measure of the survey included: identifying how physicians and pharmacists handle prescribing or dispensing COCs along with broad-spectrum antibiotics. Gender, educational degree, and years in practice were also collected. RESULTS A total of 182 participants returned the surveys (57% were physicians and 43% were pharmacists). When asked if broad-spectrum antibiotics have a clinically significant interaction with COCs, 82.7% of physicians and 88.5% of pharmacists answered, "yes". Of the respondents, 84.6% stated that the drug interaction warrants the patient to be advised to use back-up contraception. A total of 90.1% stated that they currently instruct patients to use back-up contraception when prescribing or dispensing antibiotics to a patient who is on COC, with no statistically significant difference existing between the responses of the pharmacists and the physicians. CONCLUSION Physicians and pharmacists believe that broad-spectrum antibiotics decrease the effectiveness of COCs. These practitioners warn their patients of this interaction and advise the use of back-up contraception. More education should be provided to practitioners regarding the data concerning COCs and broad spectrum antibiotics and lack of a proven interaction.