Reproductive pharmacology and therapeutics Flashcards
what occurs in the follicular phase?
= proestrus and oestrus. dominant follicle develops in ovary and secretes oestrogen. This triggers GnRH release and a surge in LH from the pituitary gland leading to ovulation.
what occurs in the luteal phase?
= metoestrus and dioestrus. CL develops and secretes progesterone, prepares uterus for pregnancy and if not pregnant, uterus secretes PGF2a to cause luteolysis
list situations where reproductive drugs are used in large animals
synchronisation and stimulation of oestrus and ovulation, pregnancy termination/ induction of birth, treatment for endometritis and for problems at parturition
list situations where reproductive drugs are used in small animals
increase fertility, oestrus suppression in bitches, pregnancy termination/ treatment of pyometra, false pregnancy, problems at parturition, chemical castration, male problems e.g. benign prostatic hypertrophy
give 3 examples of GnRH analogues and describe their features
buserelin, deslorelin, gonadorelin
GnRH has a very short half-life and its release is normally pulsatile
what is the main use of GnRH and analogues?
stimulate production of gonadotrophins e.g. LH and FSH
describe how GnRH and analogues work if given as a short-acting analogue
treat infertility by stimulating FSH and LH production therefore induce ovulation/ oestrus
treat cystic ovaries in cows, cause luteinisation of follicular cysts
synchronise oestrus for AI/ ET
terminating oestrus in ferrets and cats (induce ovulation)
how does GnRH and its analogues work if given as a long-lasting analogue?
down regulation of GnRH receptors on pituitary cells so reduced production of gonadotrophins (chemical castration - implant)
what is the function of LH in males and females
males - stimulates testicular leydig cells to secrete testosterone
females - follicle development, induction of ovulation and Cl development
what is the function of FSH in males and females?
males - stimulates sertoli cells to produce proteins and nutrients for sperm
females - follicle development
what is hCG used for?
= human chorionic gonadotrophin. acts like LH so causes follicle development, induction of ovulation and development of CL
what is eCG used for?
= equine chorionic gonadotrophin. produced by endometrium to stimulate secondary CL’s. FSH-like but has LH activity
what are 2 side effects of the use of hCG/ eCG?
anaphylaxis and antibody production therefore reduced efficacy
what are gonadotrophins clinically used for?
eCG/ hCG/ FSH/ LH
treatment of infertility - induce follicular development and ovulation
treat cystic ovaries in cows and cause superovulation
induce and synchonise oestrus
used in males to reduce libido and in cryptorchidism
describe the structure of oxytocin
synthesised in the hypothalamus and released from posterior pituitary, release is stimulated via sensory nerves in vagina, cervix, and suckling
what is the function of oxytocin?
causes milk ejection from the mammary gland
stimulates frequency and force of smooth muscle contraction in the uterus
how is oxytocin administered?
IM/ IV. If given at IV then use 1/4 the dose
what is oxytocin used for clinically?
induction of labour (need fully dilated cervix/ no obstruction)
milk letdown in bitches and cows with mastitis
adrenaline reduces its affect (stress)
SE - rare. but painful contractions and poss uterine rupture at high/ repeated doses
give an example of a PGE and describe its function
give 2 examples of analogues
PGF2a, luteolytic and produced by endometrium in late diestrus/ late pregnancy.
e.g. dinoprost, luprostiol
what is a hazard of using PGEs?
can cause abortion - avoid self injection and also absorption across the skin.
also causes bronchoconstriction
what are the SE of prostaglandins in animals?
increased sm tone - diarrhoea and pain, bronchoconstriction. vasoconstriction (BP) increased risk retained placenta. only given IM
what are prostaglandin analogues used for clinically?
oestrus synchronisation - (combos)
following silent oestrus to know when to expect next
cystic ovaries (luteolysis)
induction of abortion - earlier use = better
induction of parturition - 3d after admin
treatment of endometritis - cause luteal regression and oestrus therefore less favourable conditions for bacteria. not recommended for pyo
describe properties of progestins. give examples of synthetic
progesterone rapidly absorbed intravaginally, metabolised by the liver. -ve feedback on GnRH and FSH/LH so suppresses oestrus and ovulation. (when remove sponge kick starts cycle)
e.g. altrenogest, flugestone
how are progestins used in large animals via vaginal admin?
used in cows and sheep. used in cycling animals to synchronise oestrus, non-cycling to induce and synchronise oestrus and to treat cystic ovaries in cattle
how are the intravaginal progestin devices administrated?
inserted into vagina and left for 7d, cycling cattle are given PG 24h prior to removal and non cycling aren’t, at removal oestrus stimulated. inseminate 56h after removal (PRID) or within 12h first observed oestrus (CIDR)
describe SE’s of using intravaginal progestins
don’t use 35d post-calving, vaginal wall inflammation
how are progestins used in LA via oral admin?
altrenogest
horses - suppress oestrus during non-breeding season and to control timing of start and synchronisation
pigs - synchronisation of oestrus. guilts 18d, sows 3d
describe SE of altrenogest
do not use if uterine infection present (favourable bacterial conditions), avoid handling if pregnant, wear gloves, can disrupt menstrual cycle, cause uterine cramps, bleeding, prolong pregnancy
name 3 progestin drugs used in female SA
proligestone acetate, megoestrol acetate, medroxyprogesterone acetate
describe the use of PA progestin
injection. used for oestrus control (possible permanent, -ve feedback), false pregnancy and feline flea allergy
SE = pyometra, diabetes (counteract insulin), mammary hypertrophy in queens, adrenal suppression
describe the use of MA progestin
anti-oestrogenic properties. used to postpone/ prevent oestrus in bitches and queens, flea allergy in cats, hypersexual behaviours in male dogs
SE - diabetes, mammary hyperplasia in cats
describe the use of MedA progestin
injection. prevents oestrus in bitches, given during anoestrus
SE - pyo, mammary swelling/ nodules, weight gain, diabetes, pregnant women avoid
name 2 progestins used in male small animals
delmadione acetate, osaterone
describe how delmadinone is used?
injection for D/C. treats hypersexuality, benign prostatic hyperplasia, peri-anal tumours
SE = PU/PD, weight gain, diabetics, changes to coat
describe how osaterone is used?
inhibits effects of testosterone - benign prostatic hypertrophy, blocks binding of androgens to prostatic receptors
describe the use of estriol
oestrogen based drug. used in spayed bitches to treat urinary incontinence. (increases tone of urethral sphincter)
adverse reactions - swollen vulva and mammary glands, attractive to male dogs
describe the use of aglepristone
progesterone antagonist. used for pregnancy termination in bitches and queens, medical management of pyo
SE - pain injection, early oestrus after termination, abortion may only be partial, wear gloves, anti-glucocorticoid activity (don’t use in hypo patients)
describe the use of cabergoline
prolactin inhibitor - used to treat false pregnancy in bitches and to suppress lactation
SE = V, anorexia, may abortion, hypotension
describe the use of nadrolone
anabolic steroid, banned in food animals. used occasionally for aplastic anaemia and to counteract catabolic states
SE - don’t use in pregnant, cause androgenic SE in females
describe the use of melatonin
= natural secretion from pineal gland. produced during darkness. used to manipulate earlier breeding. given to sheep as an implant
