Pharmacology of Menopause and Oral Contraceptives
A brief description of the assigned health topic.
Menopause
Defined by permanent cessation of the menstrual period
Occurs as a result of natural depletion of the ovarian oocytes
Medically, it is the absence of menstrual bleeding for 12 consecutive months
Occurs within the age of 45 to 55 years
The average age of menopause is 51 years in the United States
Surgery (hysterectomy) or damage of ovaries may result in menopause before the age of 40 years.
Also known as the climacteric, menopause is the point in time when a woman ceases to have menstrual periods permanently, and are unable to bear children again. Typically, menopause occurs due to the aging of ovarian follicles resulting in a natural depletion of the ovarian oocytes (Warren, Shu, & Dominguez, 2015). Medically, a woman is said to have experienced menopause if she has, for a period of 1 year, not had any menstrual bleeding; this marks the permanent end of fertility (Pal & Sayegh, 2017). There is no particular age when menopause occurs; in most women, it occurs within the age of 45 and 55 years (Pal & Sayegh, 2017). However, in some women, menopause may occur as early as the age of 40 years; in the United States, the average age of menopause is 51 years (Bain et al., 2018). It is important to note that menopause may also occur before the age of 40 years due to other factors such as surgery, for instance, hysterectomy where the ovaries are removed, or when the ovaries are damaged for example as a result of chemotherapy (Panay, Briggs, & Kovacs, 2020).
Oral Contraceptives
Medications are taken by mouth to prevent pregnancy
They contain hormones, usually progestin, and estrogen
They prevent fertilization by thickening cervical mucus, blocking ovulation, and changing the lining of the uterus
The two major types are; progestogen-only pill and combined oral contraceptive pill
Centchroman or ormeloxifene is a rare oral contraceptive; it acts on estrogen receptor
Also known as birth control pills, oral contraceptives are medications taken by mouth to prevent pregnancy. These medications usually contain hormones, especially progestin, and estrogen, that prevent fertilization of eggs by thickening cervical mucus (this prevents sperms from reaching the egg), inhibiting ovulation or rather the release of eggs from the ovaries, and at times changing the uterus lining which discourages implantation (Cooper, Adigun, & Shamoon, 2019). There are two major types of oral contraceptives; the progestogen-only pill (recommended for individuals who are affected by estrogen hormone), and combined oral contraceptive pill (contains both progestin and estrogen) (Speroff, & Darney, 2011). Apart from the two types, there is another rare type of oral contraceptive known as the Centchroman, or ormeloxifene; it acts on estrogen receptor (selective estrogen receptor) and is usually taken once a week (Kamboj, Ray, & Anand, 2018).
A brief description of the pathophysiology related to the assigned health topic.
Menopause
Aging of ovaries results in the reduction of the quality and quantity of follicles
This causes shrinking of the follicle cohort size
The ovaries response to luteinizing hormone (LH), and follicle-stimulating hormone (FSH) reduces
Production o progesterone decreases, ovulations become fewer ovulations, and follicular phase becomes shorter
the number of viable follicles decreases due to above normal levels of level of estradiol
Due to very little production of estradiol, the menstruation cycles cease permanently
The pathophysiology of menopause begins with the gradual loss of the sensitivity of the ovaries to the stimulation by the gonadotropin, a hormone that is directly related to the follicular attrition. As the ovaries age, the quality and quantity of follicles declines; this is particularly because, throughout the life cycle of a woman, the oocytes in the ovaries undergo atresia (O’Neill, & Eden, 2017). As a result, the follicle cohort size shrinks (Bain et al., 2018). Consequently, the response of the ovaries to the luteinizing hormone (LH) and follicle-stimulating hormone (FSH) decreases. This causes decreased progesterone production, fewer ovulations, and shorter follicular phase (with less regular, and shorter menstrual cycles). The luteal out-of-phase (LOOP) and double ovulation events occur and, in most cases, cause the level of estradiol to be above normal. This decreases the number of viable follicles, and eventually, the follicles that remain do not respond. The ovaries also produce very little estradiol to the extent that menstruation stops permanently.
Oral Contraceptives
Main hormones: progesterone, and estrogen
Progesterone main mechanism of action (negative progestogen feedback):
Prevention of the growth and development of endometrial
Development of scant and viscous cervical mucus
Suppression of ovulation
Suppression of the LH surge
Estrogen main mechanism of action (estrogen negative feedback):
Slows down the secretion of FSH which inhibits the growth of follicles
The hormone that is primarily responsible for pregnancy prevention is progesterone. Through negative progestogen feedback, initiated by the hypothalamus, the gonadotropin-releasing hormone (GnRH) pulse frequency is decreased; consequently, this mechanism reduces the secretion of FSH and greatly decreases the secretion of LH by the anterior pituitary (Cooper, Adigun, & Shamoon, 2019). Due to the decrease in the levels of FSH, the development of the follicular is inhibited, which consequently prevents an increase in the levels of estradiol (estradiol is produced by follicle) (Cooper, Adigun, & Shamoon, 2019). Consequently, a mid-cycle LH surge is prevented by the lack of estrogen positive feedback on LH secretion as well as the Progestogen negative feedback. Finally, ovulation is prevented by the absence of an LH surge, and inhibition of follicular development (Cooper, Adigun, & Shamoon, 2019).
Oral contraceptives containing progestogen also prevent fertilization by increasing the cervical mucus viscosity and decreasing its water content; this mechanism prevents the penetration of the sperm into the upper genital tract (fallopian tubes and uterus) through the cervix (Cooper, Adigun, & Shamoon, 2019). Additionally, the endometrial atrophy induced by contraceptives containing progesterone deters implantation; however, there is insufficient evidence or rather no proof that this occurs (Cooper, Adigun, & Shamoon, 2019).
Equally, estrogen negative feedback on the anterior pituitary inhibits the development of follicles by slowing down the secretion of FSH; however, this effect is not as prominent as that of progesterone (Cooper, Adigun, & Shamoon, 2019).
The primary clinical manifestations (signs and symptoms) of the assigned health topic.
Signs and Symptoms of menopause
Signs and Symptoms of Menopause
Shorter menstrual cycles
A benign sore (lesion or polyp)
Spotting or bleeding
Dysfunctional uterine bleeding
Irregular bleeding (spotting, heavier, lighter)
Loss of breast fullness
Slowed metabolism and weight gain
Mood changes
Chills
Atrophic vaginitis (Thinning of the membrane of the outer urinary tract, cervix, vagina, and vulva)
Viginal dryness
Painful intercourse
Hot flashes
Heavy night sweats
Interrupted sleeping patterns
Urinary urgency
Urinary incontinence
Dry skin and thinning hair
joint and muscle pain
poor memory, anxiety, irritability, and inability to concentrate
Breast tenderness and reduction
Depression
Headache
Heart palpitations
Back pain (O’Neill, & Eden, 2017; Panay, Briggs, & Kovacs, 2020)
Since menopause results from severely reduced functioning of the ovaries, and depletion of ovarian oocytes/follicles, it is associated with lower levels of reproductive hormones, especially estrogen. The low levels of estrogen is the major cause of a majority of the signs and symptoms of menopause ranging from skin changes (decreased elasticity and thinning), genital tract atrophy (urinary incontinence, painful intercourse, vaginal dryness), insomnia, psychological changes (difficulty concentrating, depression, mood swings), and vasomotor instability (night sweats and hot flushes) (O’Neill, & Eden, 2017; Panay, N., Briggs, & Kovacs, 2020). The loss of sex drives is mainly contributed by lower levels of androgen (O’Neill, & Eden, 2017).
Adverse (Side) Effects of Oral Contraceptives
Amenorrhea
Breakthrough bleeding
decreased libido
leukorrhea (increase in vaginal discharge)
mastalgia (breast tenderness)
abdominal cramping
Headaches and migraine
Nausea
swelling of the ankles/feet (fluid retention)
Weight Change
Bloating
Inter-menstrual spotting (Cooper, Adigun, & Shamoon, 2019)
Most of the adverse effects of oral pills are due to the female body trying to adjust to the different levels of hormones. For instance, as the uterus adjusts to a thinner endometrial as a result of the oral contraceptive hormones, inter-menstrual bleeding may be observed. Further, the oral pills may cause fluid retention may occur, particularly around the hips and breast,s and this may result in weight gain (Cooper, Adigun, & Shamoon, 2019). The oral contraceptive may cause thyroid and hormonal abnormalities, which may result in missed periods. However, a majority of these symptoms resolve with time.
The pharmacologic agents (drugs) used in the treatment of the assigned health topic, with a focus on:
Clonidine
Indications: 0.1 mg PO once daily at bedtime or 0.05 mg PO twice daily
Classifications: antihypertensive medications
Mechanisms of Action: Acts centrally as an agonist on alpha-2 adrenergic
Adverse Effects: tiredness, dizziness, dry eyes, dry mouth, confusion, heart arrhythmias, nausea, constipation, sexual dysfunction (Yasaei, & Saadabadi, 2019).
Clonidine is an antihypertensive medication taken in doses of 0.1 mg PO once daily at bedtime or 0.05 mg PO twice daily to treat vascular migraine headaches and control of hot flashes in menopause among others because of its effect on the sympathetic nervous system, particularly by reducing circulation of epinephrine (Yasaei, & Saadabadi, 2019). Being an imidazoline derivative, clonidine acts centrally on alpha-2 adrenergic as an agonist in the nucleus tractus solitarii (NTS). The drug works by exciting a pathway that causes inhibition of excitatory cardiovascular neurons. Due to its alpha-antagonist effect in the medulla and posterior hypothalamus, clonidine reduces, from the central nervous system (CNS), the sympathetic outflow; clinically, this mechanism results in a reduction of arterial blood pressure (Yasaei, & Saadabadi, 2019).
Gabapentin (gralise)
Indications: 300 mg/day PO initially; if the patient is unresponsive 300 mg three times daily titration PO is recommended (total 900 mg/day)
Classifications: Anticonvulsants, Gabapentinoids
Neuropathic Pain and Peripheral Neuropathy Agents
Mechanisms of Action: Unknown, it is suspected to inhibit neuronal calcium currents in vitro
Adverse Effects: loss of balance or coordination, back pain, pain in the extremities, weight gain, urinary tract infection, runny or stuffy nose, dry mouth, breast swelling, blurred vision, indigestion, nausea, constipation, diarrhea, swelling of the extremities, headache, tired feeling, weakness, drowsiness, sleepiness, spinning sensation (vertigo) or dizziness (Pinkerton et al., 2014).
Gabapentin, particularly gralise, is an anticonvulsant used to treat hot flashes and vasomotor symptoms in menopause women. The initial recommended dose is 300g/day PO; however, some patients may still experience hot flashes at this level of dosage; in this case, a titration of 300mg three times a day is recommended (Pinkerton et al., 2014). The mechanism of action for Gabapentin is unknown; however, it was designed to mimic the neurotransmitter GABA. It is suspected that the drug inhibits the alpha 2-delta subunit of voltage-gated calcium channels hence relieving neuropathic pain by up-regulating the biding site (i.e, the α2 δ subunit of voltage-gated calcium channels) (Pinkerton et al., 2014). Through the same mechanism, it is believed that, as a result of the estrogen withdrawal, the up-regulation of the gabapentin binding site is involved in the hypothalamus; consequently, this leads to the increase in the activity of the neurotransmitters in the hypothalamus (Pinkerton et al., 2014). B this mechanism, Gabapentin is believed to exert its effect on hot flashes (Pinkerton et al., 2014).
Venlafaxine
Indications: I week dosage of 37.5 mg PO taken once each day; this is followed by titration to 75 mg PO once daily.
Classifications: Serotonin Norepinephrine Reuptake Inhibitor Antidepressants (SNRIs)
Mechanisms of Action: inhibits the central reuptake of norepinephrine, and serotonin
Adverse Effects: sexual problems, sweating, dry mouth, constipation, loss of appetite, and increased risk of serotonin syndrome, mania, and suicide (Caan et al., 2015; Shelton, 2018).
Venlafaxine is an SNRI that starts with a one week dose of 37 mg PO once each day, followed by titration of 75 mg PO once daily to reduce the frequency of vasomotor symptoms associated with menopause as well as decrease the severity of hot flashes (Prescribers Digital Reference, 2020). There is no clear mechanism of how venlafaxine relieves hot flashes. However, this pharmacologic agent blocks together with desvenlafaxine (venlafaxine major active metabolite), inhibit the re-uptake of both serotonin and norepinephrine, which are key neurotransmitters leaving them active but in the synapse (Shelton, 2018). Long-term neurotransmitter receptor modulation by venlafaxine is said to be effective in reducing vasomotor symptoms and hot flashes because of the delay in therapeutic response (Caan et al., 2015).
References
Bain, J., Bragg, S., Ramsetty, A., & Bradford, S. (2018). Endocrine Conditions in Older Adults: Menopause. FP essentials, 474, 20-27.
Caan, B., LaCroix, A. Z., Joffe, H., Guthrie, K. A., Larson, J. C., Carpenter, J. S., … & Reed, S. (2015). Effects of estrogen or venlafaxine on menopause-related quality of life in healthy postmenopausal women with hot flashes: a placebo-controlled randomized trial. Menopause 22(6), 607
Cooper, D. B., Adigun, R., & Shamoon, Z. (2019). Oral Contraceptive Pills. In StatPearls. StatPearls Publishing.
Kamboj, V. P., Ray, S., & Anand, N. (2018). Centchroman: A safe, reversible postcoital contraceptive with curative and prophylactic activity in many disorders. Frontiers in Bioscience (Elite Edition), 10, 1-14.
O’Neill, S., & Eden, J. (2017). The pathophysiology of menopausal symptoms. Obstetrics, Gynaecology & Reproductive Medicine, 27(10), 303-310.
Pal, L., & Sayegh, R. A. (Eds.). (2017). Essentials of Menopause Management: A Case-Based Approach. Springer.
Panay, N., Briggs, P., & Kovacs, G. T. (Eds.). (2020). Managing the Menopause. Cambridge University Press.
Pinkerton, J. V., Kagan, R., Portman, D., Sathyanarayana, R., Sweeney, M., & Breeze, 3 Investigators. (2014). Phase 3 randomized controlled study of gastroretentive gabapentin for the treatment of moderate-to-severe hot flashes in menopause. Menopause, 21(6), 567-573.
Prescribers Digital Reference (PDR) LLC,2020. (2020). Horizant | Drug Information | PDR.net. Retrieved from https://www.pdr.net/drug-information/horizant?druglabelid=196
Shelton, R. C. (2018). Serotonin and norepinephrine reuptake inhibitors. In Antidepressants (pp. 145-180). Springer, Cham.
Speroff, L., & Darney, P. D. (2011). A clinical guide for contraception. Lippincott Williams & Wilkins.
Warren, M. P., Shu, A. R., & Dominguez, J. E. (2015). Menopause and hormone replacement. In Endotext. MDText. Com, Inc.
Yasaei, R., & Saadabadi, A. (2019). Clonidine. In StatPearls. StatPearls Publishing.