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.
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).
|
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).
|
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).
|
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).
|
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).
|
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).
|
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).
|
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).
|
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).
|
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).
|