Nuvaring(reg): No Interaction with Broad-Spectrum Antibiotics Avoids the Need for Back Up Contraceptive Measures

Main Category: Women's Health / Gynecology
Article Date: 06 Apr 2005 - 12:00 PDT

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NuvaRing(reg), the once-a-month contraceptive ring from Organon, does not interact with two commonly used broad-spectrum antibiotics, according to new results published in Clinical Pharmacokinetics. As a result of the findings, the 14 European countries that participate in the Mutual Recognition Procedure for NuvaRing(reg), have approved changes to the official European prescribing information such that NuvaRing(reg) users no longer need to use back up contraception when taking either amoxicillin or doxycycline. [1]

"This absence of interaction with amoxicillin and doxycycline adds further to the convenience of NuvaRing," said Prof. Dr. Cosima Brucker, gynecologist, Nurnberg, Germany. "Furthermore, this along with the fact that vomiting does not affect the contraceptive efficacy of NuvaRing and its once-a -month action reduces the chances of unplanned pregnancy in real-life as a result of user error."

Interactions between antibiotics and combined oral contraceptives were first reported several decades ago. Concurrent use may reduce contraceptive efficacy leading to bleeding irregularities and unplanned pregnancies. As a result, women using the combined pill are advised to take additional contraceptive precautions while taking a short course of broad-spectrum antibiotics and for the next 7 days after stopping.

Such interactions have been assumed for NuvaRing but viewed as unlikely since the vaginal route of administration avoids first-pass metabolism, potential food effects and gastrointestinal adverse effects. However, no pharmacokinetic data have until now been available to support this view.

Two pharmacokinetic studies were therefore performed to investigate possible interaction between NuvaRing and concomitant treatment with orally administered amoxicillin or doxycycline. Amoxicillin and doxycycline are among the most commonly used of the penicillin and tetracycline groups of antibiotics respectively.

A group of healthy women (n=16) were randomized to 21 days of treatment with NuvaRing either alone or with oral amoxicillin (875 mg twice daily for days 1-10) after which they entered a 7-day washout period and were crossed to the alternate treatment. The second study used the identical design but subjects (n=16) received oral doxycycline (100mg once daily, days 1-10).

No differences in serum concentrations of the hormones released by NuvaRing - ethinyl estradiol and etonogestrel - were observed between subjects using NuvaRing alone and those receiving concomitant antibiotic treatment. This indicates the absence of pharmacokinetic interactions suggesting that contraceptive efficacy would also be unaffected. NuvaRing was well tolerated in both studies either alone or in combination with the antibiotic.

Organon - with shared head offices in Roseland, NJ, USA and Oss, The Netherlands - creates, manufactures and markets prescription medicines that improve the health and quality of human life. Through a combination of independent growth and business partnerships, Organon strives to remain or become one of the leading pharmaceutical companies in each of its core therapeutic fields: reproductive medicine, psychiatry and anesthesia.

Organon products are sold in over 100 countries, of which more than 60 have an Organon subsidiary. Organon is the human health care business unit of Akzo Nobel.

1. The 14 European countries that participate in the Mutual Recognition Procedure for NuvaRing agreed to change to the official European prescribing information in August 2004. The next step is to implement the new prescribing information by the national regulatory authorities before being applicable in individual countries. In the US and other countries worldwide, the local approved labeling should be followed until the review of the proposed labeling by local authorities is completed.

http://www.organon.com

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