Protection of Conscience Project
Protection of Conscience Project
www.consciencelaws.org
Service, not Servitude

Service, not Servitude

FDA Approved Methods of Birth Control

Mechanisms of Action

Sean Murphy*

Introduction

The U.S. Food and Drug Administration (FDA) approves drugs and devices that are used for birth control.  It offers a list of different kinds of birth control in a Birth Control Guide.

The mechanism of action of birth control is morally significant for many people.  Those who have no concern about mechanisms that may prevent fertilization (contraception) may have moral or ethical objections to methods that can cause the death of an embryo, either before implantation (embryocide) or after (abortifacient).

For this reason, manufacturers' statements about the mechanism of action are reproduced below, with links to the original statements.  Note that only a single product is used as an example under each category.

Key terms are colour coded to distinguish between contraceptive and embryocidal effects.  For an explanation of this terminology, see Clearing Rhetorical Minefields.

Implantable Rod

Example:  implanon®
Manufactuer's statement on clinical pharmacology: 12.1 Mechanism of Action

The contraceptive effect of IMPLANON is achieved by suppression of ovulation, increased viscosity of the cervical mucus, and alterations in the endometrium.

Source:  Full Prescribing Information (Revised February, 2012), N.V. Organon, a subsidiary of Merck & Co. Inc.

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

Copper IUD

Example:  ParaGard®
Manufacturer's Prescribing information

Clinical Pharmacology:  The contraceptive effectiveness of ParaGard® is enhanced by copper continuously released into the uterine cavity. Possible mechanism(s) by which copper enhances contraceptive efficacy include interference with sperm transport or fertilization, and prevention of implantation.

Manufacturer's Information for patients

How does ParaGard work?

Ideas about how ParaGard® works include preventing sperm from reaching the egg, preventing sperm from fertilizing the egg, and preventing the egg from attaching (implanting) in the uterus.

Source: Prescribing Information, ParaGard® T 380A, Intrauterine Copper Contraceptive.  TEVA WOMEN'S HEALTH, INC. Subsidiary of TEVA PHARMACEUTICALS USA, INC. Sellersville, PA 18960 (Accessed 2012-02-22)

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

Hormonal IUD

Example: Mirena®
Manufacturer's statement on clinical pharmcology: 12.1 Mechanism of Action

The local mechanism by which continuously released levonorgestrel enhances contraceptive effectiveness of Mirena has not been conclusively demonstrated. Studies of Mirena prototypes have suggested several mechanisms that prevent pregnancy: thickening of cervical mucus preventing passage of sperm into the uterus, inhibition of sperm capacitation or survival, and alteration of the endometrium.

FDA-Approved Patient Information: How does Mirena work?

It is not known exactly how Mirena works. Mirena may work in several ways. It may thicken your cervical mucus, thin the lining of your uterus, inhibit sperm movement and reduce sperm survival. Mirena may stop release of your egg from your ovary, but this is not the way it works in most cases. Most likely, these actions work together to prevent pregnancy. Mirena can cause your menstrual bleeding to be less by thinning the lining of the uterus.

Source: Mirena® (levonorgestrel-releasing intrauterine system) Bayer HealthCare Pharmaceuticals (Accessed 2012-02-22)

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

Birth Control Shot

Example: Depo-Provera®
Manufacturer's statement on clinical pharmacology: 12.1 Mechanism of Action

Depo-Provera CI (medroxyprogesterone acetate [MPA]), when administered at the recommended dose to women every 3 months, inhibits the secretion of gonadotropins which, in turn, prevents follicular maturation and ovulation and results in endometrial thinning. These actions produce its contraceptive effect.

This Patient Information has been approved by the U.S. Food and Drug Administration.

Source: Full Prescribing Information (Revised July, 2011), Pharmacia & Upjohn Company, A Division of Pfizer Inc. NY, NY 10017 (Accessed 2012-02-24)

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

Oral Contraceptives: Combined Pill

Example: YAZ®
Manufacturer's statement on clnical pharmacology: 12.1 Mechanism of Action

COCs lower the risk of becoming pregnant primarily by suppressing ovulation. Other possible mechanisms may include cervical mucus changes that inhibit sperm penetration and the endometrial changes that reduce the likelihood of
implantation.

Source:  Full Prescribing Information, Bayer HealthCare Pharmaceuticals Incorporated (Accessed 2012-02-23)

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

Oral Conraceptives: Progestin-Only (POP, mini-pill)

Example: ortho micronor® :Manufacturer's statement on clinical pharmacology: 1. Mode of Action

Ortho Micronor® progestin-only oral contraceptives prevent conception by suppressing ovulation in approximately half of users, thickening the cervical mucus to inhibit sperm penetration, lowering the midcycle LH and FSH peaks, slowing the movement of the ovum through the fallopian tubes, and altering the endometrium.

Source:  Ortho Micronor Description (Revised July, 2008) Ortho-McNeil-Janssen Pharmaceuticals, Inc.

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

Vaginal contraceptive ring

Example: nuvaring®
Manufacturer's statement on clinical pharmacology

Combination hormonal contraceptives act by suppression of gonadotropins. Although the primary effect of this action is inhibition of ovulation, other alterations include changes in the cervical mucus (which increase the difficulty of sperm entry into the uterus) and the endometrium (which reduce the likelihood of implantation).

Source:  NuvaRing Description (Revised November, 2012) N.V. Organon, a subsidiary of Merck & Co., Inc (Accessed 2012-02-23)

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

Patch

Example:  Ortho Evra®
Manufacturer's statement on clinical pharmacology: Pharmacodynamics

Norelgestromin is the active progestin largely responsible for the progestational activity that occurs in women following application of ORTHO EVRA®. . .

Combination oral contraceptives act by suppression of gonadotropins. Although the primary mechanism of this action is inhibition of ovulation, other alterations include changes in the cervical mucus (which increase the difficulty of sperm entry into the uterus) and the endometrium (which reduce the likelihood of implantation).

Source:  ORTHO EVRA® (norelgestromin / ethinyl estradiol TRANSDERMAL SYSTEM) (Revised December, 2011) Ortho Women's Health & Urology, Division of Ortho-McNeil-Janssen Pharmaceuticals, Inc.

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

The after-sex pill: progestin only

Example: Plan B One-step®
Manufacturer's statement on clinical pharmacology: 12.1 Mechanism of Action

Emergency contraceptive pills are not effective if a woman is already pregnant. Plan B One-Step is believed to act as an emergency contraceptive principally by preventing ovulation or fertilization (by altering tubal transport of sperm and/or ova). In addition, it may inhibit implantation (by altering the endometrium). It is not effective once the process of implantation has begun.

Source:  Full Prescribing Information (Revised July, 2009) Gedeon Richter, Ltd., Budapest, Hungary for Duramed Pharmaceuticals, Inc., Subsidiary of Barr Pharmaceuticals, Inc. (Accessed 2012-02-23)

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

The after-sex pill: antiprogestin

Example: Ella
Manufacturer's statement on clinical pharmacology: 12.1 Mechanism of Action

When taken immediately before ovulation is to occur, ella postpones follicular rupture. The likely primary mechanism of action of ulipristal acetate for emergency contraception is therefore inhibition or delay of ovulation; however, alterations to the endometrium that may affect implantation may also contribute to efficacy.

Source:  Full Prescribing Information (Revised August, 2010) Watson Pharma, Inc. (Accessed 2012-02-23)

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).

The after-sex pill: estrogen & progestin

Example: Aviane 28
Manufacturer's statement on clinical pharmacology: Mode of Action

Combination oral contraceptives act by suppression of gonadotropins. Although the primary mechanism of this action is inhibition of ovulation, other alterations include changes in the cervical mucus (which increase the difficulty of sperm entry into the uterus) and the endometrium (which reduce the likelihood of implantation).

Source:  Aviane 28 Description (Revised September, 2009) Barr Laboratories Inc.

    Contraceptive effect
    Embryocidal effect

"In summary, the primary contraceptive effect of all the non-barrier methods, including emergency use of contraceptive pills, is to prevent ovulation and/or fertilization. Additional contraceptive actions for all of these also may affect the process beyond fertilization but prior to pregnancy. For some methods these actions may be significant in contributing to their overall contraceptive efficacy." American College of Obstetricians and Gynecologists, Equity Toolkit (Accessed 2012-02-26). From ACOG Statement on Contraceptive Methods (July, 1998).