The contraceptive vaginal ring, nuvaring, shows no interaction with broad spectrum oral antibiotics

Two studies were performed to investigate whether ethinylestradiol (EE) and etonogestrel (ENG) released from NuvaRing (NR) are affected by concomitant treatment with the antibiotics amoxicillin (A) and doxycycline (D). Sixteen healthy women per study (age: 18 to 40 yrs.) were randomised to 21 days of treatment with NuvaRing, either alone (control) or concomitantly with amoxicillin (875 mg twice daily for 10 days, study I) or doxycycline (100 mg once daily for 10 days, study II). After a 7-days washout they were crossed over to the alternate treatment. Based on serum EE and ENG levels, area under the curve (AUC) values over 12 hours (amoxicillin) or 24 hours (doxycycline) on days 1 and 10 and for the whole of days 1-11 and days 1–22 were calculated and tested for interactions based on FDA guidance. Geometric mean results of the various AUCs (ng.h.mL−1) are presented in the following table. Calculation of EE and ENG interaction/control ratios plus 90% confidence intervals confirmed the absence of PK interactions for both antibiotics. In both studies, NuvaRing with or without concomitant antibiotic therapy was well tolerated. These studies show an absence of PK interactions between NuvaRing and concomitant broad-spectrum antibiotics and indicate that NuvaRing is a reliable contraceptive option even in situations where users may require antibiotic treatment. Clinical Pharmacology & Therapeutics (2004) 75, P33–P33; doi: 10.1016/j.clpt.2003.11.124 Table 1.  study I AUCday1 AUCday10 AUCday1–11 AUCday1–22 EE NR 0.32 0.25 5.58 11.1 NR + A 0.32 0.24 5.30 10.9 ENG NR 11.1 24.4 427 950 NR + A 10.2 24.9 427 959 study II AUCday1 AUCday10 AUCday1–11 AUCday1–22 EE NR 0.61 0.51 5.28 10.8 NR + D 0.58 0.48 5.02 10.3 ENG NR 19.9 42.7 363 811 NR + D 21.0 43.1 371 827