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Chapter 24

PHAR 100 Chapter Notes - Chapter 24: Contraceptive Patch, Hormonal Contraception, Breakthrough Bleeding

Pharmacology and Toxicology
Course Code
PHAR 100
Bill Racz

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Lesson E6 Regulation of Fertility
- Describe the hormonal regulation of female and male fertility
- Describe the mechanism of action of contraceptive agents (hormonal and device)
- List the common adverse effects associated with hormonal contraception
- List the contraceptives in order of efficacy
- Describe the social impact of the oral contraceptives
- List the advantages and disadvantages of methods of contraception
Fertility control methods
- Contraceptive’s are used to prevent conception in addition to post-coital contraceptives
and termination of pregnancy (abortion)
Ovarian Cycle:
- Day 1/beginning of the cycle: plasma levels of estrogen and progesterone are low,
endometrium is sloughed (menstruation)
o In response to the low levels of estrogen and progesterone, the hypothalamus
secretes gonadotropin releasing factor (GFR)
o GFR stimulates the anterior pituitary releasing follicle stimulating hormone
(FSH) and luteinizing hormone (LH)
o FSH ovarian follicles containing one ovum each, follicle begins to enlarge
- Day 5-6: one of the stimulated follicles begins to develop more rapidly while the others
o The maturing follicle begins to secrete estrogen
- Day 14 (ovulation): Estrogen release from the maturing follicle reaches its maximum
o LH secretion peaks stimulating the follicle to grow more rapidly
o Leads to the release of the ovum
o After ovulation, the ovum is transported by the fimbriae into the fallopian tubes
into the uterus (area of fertilization)
- During maturation, estrogen and progesterone are preparing the endometrium (lining of
the uterus) for the arrival of the fertilized ovum
- During the first 14 day, estrogen influences the growth/thickening of the endometrium
- Prior to day 14 the ovary (corpus luteum) begins to secrete increasing amounts of
progesterone progesterone stimulates the endometrium to secrete nutrients needed to
support the ovum
- Day 24-28: corpus luteum ceases to function, progesterone secretion diminishes and the
endometrium loses hormonal support leading to menstruation
- If the endometrium is not suitable, implantation and therefore conception will not occur
- If the endometrium is suitable, pregnancy occurs and the uterus will secrete large
amounts of estrogen and progesterone (maintains the endometrium)
Female Contraceptives
- Modify the ovarian cycle
- Oral contraceptives usually refer to estrogen and progestin (progesterone-like compound)
containing products most effective contraceptives; approx. 20 million North
Americans are on this product
- Phasic preparations have gained popularity and the total dose of exogenous hormone is
reduced (essentially 100% effective)
- Progestin alone agents are approx. 98% effective with more adverse effects yet suitable
for individuals unable to take estrogens
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Types of hormonal preparations include:
- Fixed combinations of estrogen and progestin
o First developed in 1955 (Pincus and Rock, Puerto Rico)
o 1961 Enovid-E first available in Canada
o Counting day 1 as mensus, compound is to be taken on the 5th and 25th day of
each cycle
- Multiphasic (biphasic and triphasic) preparations
o Contain fixed amounts of estrogen
o Contain variable amounts of progestin which increase from week to week
o Hormone dose is kept to a minimum and adverse events are believe to be reduced
in comparison to fixed-dose combinations
o Hormonal sequence closely mimics the pattern of natural hormonal release
o Drug of choice
- Continuous estrogen progestin preparations
o Combination of estrogen progestin products taken for 28 days
o No drug free period
- Transdermal contraceptive patch
o Contains ethinyl estradiol and norelgestromin (progestin)
o Patch applied to the skin for 7 day periods
o 3 per cycle
o Same mechanism of action as combined estrogen progestin oral contraceptives
- Low-dose progestin/mini-pill
o Contains synthetic progestin (ie. norethindrone)
o Daily dose
o Adverse: Breakthrough bleeding
o Less effective than combination products
- Norplant
o Silicone tube filled with L-norgestrel (progestin) implanted under the skin
o 5 year use
o Approx. $700 (equivalent to using an estrogen progestin combination for 3 years)
- Depoprovera
o Injectable progestin every three months
o Maintains effect for approx. 3 months
Mechanism of action (hormonal contraceptives)
- Estrogen-progestin combinations
o Essentially the same for fixed ration products and phasic products
o Estrogen inhibits the release of GNRH from the hypothalamus pituitary does
not stimulate the release of FSH and LH
o Progestin causes the secretions of the endocervical glands to be a thick, scant
fluid throughout the ovarian cycle inhibits migration of sperm
o Preparation of the endometrium is not optimal for implantation of a fertilized
- Low-dose progestin and Norplant and DepoProvera
o Progestin inhibits the release of GNRH and thus ovulation
o Endometrium is not fully developed; not suitable for implantation
o Progestin alters secretions of the endocervical gland inhibits migration of
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