NuvaRing does not interact with oral antibiotics

NuvaRing does not interact with oral antibiotics

P. Dogterom (1), M.M. van den Heuvel (1), T. Thomsen (2), C. Verhoeven


Department of Clinical Pharmacology and Kinetics, NV Organon, Oss, The

Netherlands (1); Pharm PlanNet Contract Research GmbH, Mönchengladbach, Germany

(2); Department of Clinical Development, NV Organon, Oss, The Netherlands (3)

Introduction: Oral antibiotics are commonly thought to lower the

contraceptive efficacy of combined oral contraceptives, though recent literature

suggests a lack of interaction. NuvaRing is a monthly contraceptive vaginal ring

that continuously releases 15 µg ethinylestradiol (EE) and 120 µg etonogestrel

(ENG) daily. The hormones are absorbed through the vaginal mucosa into the

bloodstream, thereby avoiding hepatic first-pass effect. Two trials were

conducted to investigate whether serum concentrations of EE and ENG released

from NuvaRing are affected by concomitant treatment with the oral antibiotics

amoxicillin or doxycycline.

Design and Methods: Two randomized, open-label, crossover trials were

performed at a single centre in Germany. In one study, 16 healthy female

volunteers (age 18–40 years) were randomized to 21 days of NuvaRing treatment

either alone or concomitantly with amoxicillin (875 mg twice daily on days 1–10)

followed by a 7-day, ring-free washout, before being crossed over to the

alternate treatment. The other study was identical except that doxycycline (100

mg once daily on days 1–10) replaced amoxicillin. Concentrations of

circulating EE and ENG were measured over various periods up to and including

days 1–22.

Results: Fifteen subjects completed each study. During the relevant

treatment periods in both studies, the patterns of circulating EE and ENG

concentrations with NuvaRing alone were comparable with those for NuvaRing plus

the relevant antibiotic. Analysis of area under the curve (AUC) values (day 1,

day 10, days 1–11 and days 1–22) confirmed the absence of pharmacokinetic

interactions with both antibiotics. The AUC (mean+SD in ng h/ml) for EE

over days 1–22 was similar for NuvaRing with amoxicillin (11.3+3.6) or

doxycycline (10.9+3.9) compared with NuvaRing alone (11.7+3.9 and

11.2+3.1, respectively). The AUC (mean+SD in ng h/ml) for ENG over

days 1–22 was also comparable for NuvaRing with amoxicillin (992+241)

or doxycycline (853+202) and NuvaRing alone (973+193 and 824+149,

respectively). NuvaRing was well tolerated in both studies.

Conclusions: The studies show that there is no interaction between EE

and ENG administered vaginally with NuvaRing and oral amoxicillin or doxycycline

when used concomitantly. Pharmacodynamic and large efficacy studies have

previously shown NuvaRing to be a reliable and robust contraceptive method. The

present data further support NuvaRing’s reliability since NuvaRing can be used

concomitantly with amoxicillin and doxycycline and possibly other broad spectrum

oral antibiotics.

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