Reproductive pharmacology and therapeutics

Question 1

what occurs in the follicular phase?

Answer 1

= 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.

Question 2

what occurs in the luteal phase?

Answer 2

= metoestrus and dioestrus. CL develops and secretes progesterone, prepares uterus for pregnancy and if not pregnant, uterus secretes PGF2a to cause luteolysis

Question 3

list situations where reproductive drugs are used in large animals

Answer 3

synchronisation and stimulation of oestrus and ovulation, pregnancy termination/ induction of birth, treatment for endometritis and for problems at parturition

Question 4

list situations where reproductive drugs are used in small animals

Answer 4

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

Question 5

give 3 examples of GnRH analogues and describe their features

Answer 5

buserelin, deslorelin, gonadorelin

GnRH has a very short half-life and its release is normally pulsatile

Question 6

what is the main use of GnRH and analogues?

Answer 6

stimulate production of gonadotrophins e.g. LH and FSH

Question 7

describe how GnRH and analogues work if given as a short-acting analogue

Answer 7

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)

Question 8

how does GnRH and its analogues work if given as a long-lasting analogue?

Answer 8

down regulation of GnRH receptors on pituitary cells so reduced production of gonadotrophins (chemical castration - implant)

Question 9

what is the function of LH in males and females

Answer 9

males - stimulates testicular leydig cells to secrete testosterone
females - follicle development, induction of ovulation and Cl development

Question 10

what is the function of FSH in males and females?

Answer 10

males - stimulates sertoli cells to produce proteins and nutrients for sperm
females - follicle development

Question 11

what is hCG used for?

Answer 11

= human chorionic gonadotrophin. acts like LH so causes follicle development, induction of ovulation and development of CL

Question 12

what is eCG used for?

Answer 12

= equine chorionic gonadotrophin. produced by endometrium to stimulate secondary CL’s. FSH-like but has LH activity

Question 13

what are 2 side effects of the use of hCG/ eCG?

Answer 13

anaphylaxis and antibody production therefore reduced efficacy

Question 14

what are gonadotrophins clinically used for?

eCG/ hCG/ FSH/ LH

Answer 14

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

Question 15

describe the structure of oxytocin

Answer 15

synthesised in the hypothalamus and released from posterior pituitary, release is stimulated via sensory nerves in vagina, cervix, and suckling

Question 16

what is the function of oxytocin?

Answer 16

causes milk ejection from the mammary gland

stimulates frequency and force of smooth muscle contraction in the uterus

Question 17

how is oxytocin administered?

Answer 17

IM/ IV. If given at IV then use 1/4 the dose

Question 18

what is oxytocin used for clinically?

Answer 18

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

Question 19

give an example of a PGE and describe its function

give 2 examples of analogues

Answer 19

PGF2a, luteolytic and produced by endometrium in late diestrus/ late pregnancy.
e.g. dinoprost, luprostiol

Question 20

what is a hazard of using PGEs?

Answer 20

can cause abortion - avoid self injection and also absorption across the skin.
also causes bronchoconstriction

Question 21

what are the SE of prostaglandins in animals?

Answer 21

increased sm tone - diarrhoea and pain, bronchoconstriction. vasoconstriction (BP) increased risk retained placenta. only given IM

Question 22

what are prostaglandin analogues used for clinically?

Answer 22

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

Question 23

describe properties of progestins. give examples of synthetic

Answer 23

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

Question 24

how are progestins used in large animals via vaginal admin?

Answer 24

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

Question 25

how are the intravaginal progestin devices administrated?

Answer 25

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)

Question 26

describe SE’s of using intravaginal progestins

Answer 26

don’t use 35d post-calving, vaginal wall inflammation

Question 27

how are progestins used in LA via oral admin?

altrenogest

Answer 27

horses - suppress oestrus during non-breeding season and to control timing of start and synchronisation
pigs - synchronisation of oestrus. guilts 18d, sows 3d

Question 28

describe SE of altrenogest

Answer 28

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

Question 29

name 3 progestin drugs used in female SA

Answer 29

proligestone acetate, megoestrol acetate, medroxyprogesterone acetate

Question 30

describe the use of PA progestin

Answer 30

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

Question 31

describe the use of MA progestin

Answer 31

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

Question 32

describe the use of MedA progestin

Answer 32

injection. prevents oestrus in bitches, given during anoestrus
SE - pyo, mammary swelling/ nodules, weight gain, diabetes, pregnant women avoid

Question 33

name 2 progestins used in male small animals

Answer 33

delmadione acetate, osaterone

Question 34

describe how delmadinone is used?

Answer 34

injection for D/C. treats hypersexuality, benign prostatic hyperplasia, peri-anal tumours
SE = PU/PD, weight gain, diabetics, changes to coat

Question 35

describe how osaterone is used?

Answer 35

inhibits effects of testosterone - benign prostatic hypertrophy, blocks binding of androgens to prostatic receptors

Question 36

describe the use of estriol

Answer 36

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

Question 37

describe the use of aglepristone

Answer 37

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)

Question 38

describe the use of cabergoline

Answer 38

prolactin inhibitor - used to treat false pregnancy in bitches and to suppress lactation
SE = V, anorexia, may abortion, hypotension

Question 39

describe the use of nadrolone

Answer 39

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

Question 40

describe the use of melatonin

Answer 40

= natural secretion from pineal gland. produced during darkness. used to manipulate earlier breeding. given to sheep as an implant