Pharmacological agents used in reproduction Flashcards
For General pharmacokinetics how are polypeptides and proteins used, and why?
- Shouldnt be administered orally as they are destroyed in the GI tract
- Well absorbed from injection sites
- Do not penetrate blood brain barrier
- Rapidly metabolised in the liver and kidney by proteases
- Little excreted
For General pharmacokinetics how are glycoproteins used and why?
- Destroyed in the GI tract following oral administration
- Well absorbed from injection sites
- Do not penetrate BBB
- Slowly metabolised by liver and kidneys
- No detected in urine or faeces
For General pharmacokinetics how are steroids and thyroid hormones used and why?
- Well absorbed from the gut following oral administration (need to be resistant to liver enzymes)
- Bound to plasma-binding proteins
- Evenly distributed in the body, including the CNS
- Readily excreted
Describe the mechanism of action of GnRH agonists
- Endogenous GnRH is released in pulses from the hypothalamus and binds to specific receptors in the anterior pituitary
- Pharmacological preparations given in pulses will stimulate release of FSH and LH
- Continuous release agents will cause receptor downregulation and inhibit LH and FSH release
Compare the effect of giving GnRH in pulses and continuously
Pulsatile = positive effect on GnRH, causing release of FSH and LH Continuously = Negative effect on GnRH, inhibiting release of FSH and LH
How are GnRH agonists administered?
Injectable or continuous release implants
What are the effects/examples of use for GnRH agonists?
- Used to stimulate a surge of FSH and LH, causing ovulation. This will improve conception rates and improve oestrus syncronisation
- When given continuously it supresses reproductive function, can introduce infertility in sexually mature male dogs and ferrets
Describe the mechanism of action of a GnRH vaccine
- 2 doses of GnRH vaccine given 2 weeks apart
- Induces antibodies against GnRH so can be used to chemically castrate pigs
How does having carbohydrate in a drug affect its breakdown?
The most CHO in a structure, the more resistant to breakdown by proteases, so the longer the half life
Describe the mechanism of action for gonadotropins - anterior pituitary hormones
- LH/FSH receptor agonists
- Stimulate the release of sex steroid hormones from the testis/ovary
- Given as an injection
What are the main effects and uses of gonadotropins?
- FSH/eCG promote recruitment of follicles and can be used for superovulation programs
- HCG in the female can be used to promote maturation of the follicle, ovulation and formation of the CL.
- In the male HCG stimulates the production of testosterone
What are the 3 Gonadotropins – anterior pituitary hormones?
FSH
eCG - equine chorionic gonadotropin
hCG - mostly LH activity but is cheaper and has a longer half life
What is the only licenced oestrogen receptor agonist?
Estriol - given orally
What are the main effects and uses of estriol?
- A synthetic short-acting oestrogen that is licenced to treat urethral sphincter incompetence
- Shouldn’t be used to treat entire females
What are the possible routes of administration for Progesterone receptor agonists/progestogens?
Injectable
Implants
Oral preparations
What are the main effects and uses of Progesterone receptor agonists/progestogens?
- inhibits GnRH release
- prolongs the luteal phase of the oestrus cycle
- inhibits reproductive behaviour
- can be used in oestrus synchronisation programs
- can supress oestrus
- can chemically castrate dogs
What are the main adverse effects of using Progesterone receptor agonists/progestogens?
- Endometrial hyperplasia, endometritis, pyometra
- Glucocorticoid activity may induce diabetes mellitus
- Increased thirst & appetite
Which hormones would you use/inject in a case of misalliance or wanting an abortion?
Progesterone receptor antagonists/blockers
Describe how androgen receptor agonists work in the body and their effects
- Hormone released from Leydig cells of the testis
- Binds to specific receptors with effects such as masculinising, increasing spermatogenesis, libido and secondary sex characteristics
- Can have anabolic effects such as increasing protein synthesis in skeletal muscle, increasing bone growth and increasing erythropoiesis
What are the main effects and uses of androgen receptor agonists?
Used in situations when:
- Excessive tissue breakdown has taken place
- Excessive tissue repair is needed
- Anaemia associated with renal disease
What are some adverse effects of androgen receptor agonists?
- should not be used on immature animals as may cause premature closure of growth plates
- can cause negative feedback on the hypothalamus and inhibit normal GnRH release
- Masculinisation of females
What is used to treat prostatic hyperplasia and male hypersexual behaviour?
Orally given androgen receptor antagonists (blockers)
- it is a competitive androgen receptor blocker
What are the adverse effects of using androgen receptor antagonists?
- similar structure to progesterone
- reduced ACTH stimulation
- increased appetite
- PUPD
- feminisation
What is the main effect and use of prolactin inhibitors?
Inhibits lactation
Can be used to treat false pregnancy in bitches
Given orally
