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Reproductive Pharmacology (Oestrogens (Natural forms: Oestradiol, Oestriol…
Reproductive Pharmacology
Oestrogens
Natural forms: Oestradiol, Oestriol (but these natural forms are rapidly metabolised in the liver
Synthetic:
MESTRANOL
,
STILBESTROL
and
ETHINYLESTRADIOL
( which are degraded less rapidly)
Administered with progestogen
Oral, Topical, Implantable, Intramuscular, Transdermal
Side Effects: nausea, vomiting, retention of water and salt, increased risk of throboembolism and increased risk of uterine, breast and ovarian cancer
Replacement therapy in primary ovarian cancer such as Turner's syndrome and secondary ovarian cancer such as menopause
Contraindications: oestrogen-dependent tumours, liver disease, undiagnosed genital bleeding, history of thromboembolic disorder
Progestogens
Preparations: Naturally occurring hormone (virtually inactive) and derivatives such as
HYDROXYPROGESTERONE
(administered as i.m) and testosterone derivatives such as
NORAGESTREL
(androgenic activity) and newer progestogens such as
DESOGESTREL
used in contraception with higher risk of thromoboembolism
Clinical Cases: Contraception, HRT, endometrial cancer and endometriosis(growth of tissue like endometrium beyond and outside the uterus.
SE: weak androgenic action, fluid retention, weight changes, libido changes, depression, premenstrual symptoms, irregular menstrual cycle and increased risk of thromboembolism
Anti-oestrogens
Tamoxifen
- an oestrogen antagonist (SERM) which is used to treat oestrogen-positive breast tumours. It has mild oestrogen-like SE when it acts as a partial agonist on the plasma lipids, endometrium and bone
Clomifene
- an oestrogen antagonist (SERM) which induces ovulation so it is used as infertility treatment. Inhibits oestrogen binding in the ant.pituitary. Increase in FSH and LH occurs and ovaries get stimulated.
Anti-progestogens
MIFEPRISTONE (RU486)
Acts as a competitive receptor antagonist at the progesterone receptor and in the absence of progesterone, it acts as a partial agonist at the progesterone receptor
In combination with prostaglandin E analogue-
GEMEPROST
and
MISOPROSTOL
Use: Medical termination of intrauterine pregnancies of up to 7 weeks of gestation
Contraceptions
Oral
Combined pill- oestrogen and progesterone
ETHINYLESTRADIOL
and
NORETHISTERONE
MOA: Inhibition of FSH and development of follicle due to oestrogen and inhibition of LH release and ovulation prevention with inhospitable mucus to sperm due to progestogen
Progestogen-only pill
NORETHISTERONE
and
DESOGESTREL
MOA: Makes cervical mucus inhospitable to sperm, inhibits LH release and prevents ovulation
Ovarian cysts(risk) and irregular menstruations
Long acting progestogen-only
Injectables
MEDROXYPROGESTERONE ACETATE
Intramuscular injection
Suppress ovulation and cervical mucus is thickened, preventing sperm penetration
Reduction on bone mineral density, menstrual irregularities
Subdermal transplants
ETONOGESTREL
Subcutaneously, release over 3 years
Suppress ovulation and cervical mucus is thickened
Emergency (post-coital) contraception- after unprotected intercourse of contraceptive failure
MOA: Delays/inhibits ovulation and modifies cervical mucus. Prevents ovulation in the first half of the cycle and then if ovulation has occurred, it delays the movement of the egg in the fallopian tube and thickens mucus in the second half of cycle
LEVONORGESTREL
: Progestin-only and must be taken within 72 hours. Efficacy decreases with time.
ULIPRISTAL ACETATE
: Used to prevent pregnancy upto 120 hours, it is a progesterone receptor modulator