Drugs used to Prevent Pregnancy

Question 1

Describe neuro-endocrine control

Answer 1

Hypothalamus -> GnRH -> Anterior pituitary -> FSH + LH -> Ovaries -> Oestrogen + Progesterone

Question 2

What are progestogens and oestrogen generated from?

Answer 2

Cholesterol pre-cursor

Question 3

What is the role of steroid receptors?

Answer 3

Float around cytosol -> form complex with receptor -> enters nucleus + acts as transcription regulator

Question 4

Are steroids lipid soluble?

Answer 4

Yes

Question 5

How long is the menstrual cycle?

Answer 5

28 days

Question 6

What is the menstrual cycle controlled by?

Answer 6

GnRH, FSH, LH, Oestrogen + Progesterone

Question 7

How do oestrogen and progesterone work?

Answer 7

hormone-receptor complexes bind to hormone responsive elements (HRes) = transcriptional regulation of genes

Question 8

What are the effects of oestrogen?

Answer 8

• secondary sexual characteristics
• reduced bone loss and increased bone density
• suppression of gonadotrophin from pituitary
• increased clotting factors + platelet sensitivity
• up-regulation of progesterone receptors
• ovulation + vag lubrication

Question 9

What are the effects of progesterone?

Answer 9

• suppresses maternal IS during pregnancy
• decreases uterine contractility
• promotion of hospitable endometrium for fertilised egg
• inhibits lactation
• suppression of gonadotrophin secretion
• alters viscosity + pH of cervical mucus to make inhospitable to sperm

Question 10

How do steroid analogue drugs work?

Answer 10

• uncouples normal phases of menstrual cycle = inhospitable enviro for fertilisation or no release of egg
• normal cycle suppressed as negative feedback on hypothalamus + pituitary

Question 11

How does the COCP work?

Answer 11

• highly effective
• oestrogen suppresses FSH secretion - stopping follicle development
• progestogens inhibit LH secretion - stopping ovulation + sperm traffic
• both make endometrium inhospitable

Question 12

How does the POP work?

Answer 12

• progestogens prevent sperm traffic by increasing cervical mucus viscosity + reducing pH
• chronic use of progestogens = inhibit fertilised egg implantation in endothelium

Question 13

When is the POP alternative used?

Answer 13

Where oestrogen is contraindicated

Question 14

What is emergency contraception and hoes does it work?

Answer 14

• high dose progestogen
• taken ASAP after
• affects follicular phase + prevents ovulation
• affects luteal phase by making endometrium inhospitable + affecting sperm passage

Question 15

What are the ADR’s of using oestrogen + progestogens chronically?

Answer 15

- oestrogen's increase no. of blood clotting factors in = increased risk CVD 
ADR's:
- thrombo-embolism 
- stroke 
- MI 
- risk of breast cancer
- exposure to STIs 
- hypertension 
- skin pigmentation changes 
- weight gain 
- nausea
- irregular bleeding 
- mood changes

Question 16

What are the contraindications for contraceptive drugs?

Answer 16

• already pregnant
• pre-existing CVD
• obese
• hypercholesterolaemic
• smoker over 40
• ‘oestrogen-sensitive’ breast/bowel cancer (fuelled by oestrogen acting as TF)
• liver cirrhosis

Question 17

When are abortions legal up to?

Answer 17

UK - 24 weeks

Question 18

How is Oxytocin used to terminate pregnancy?

Answer 18

• usually secreted by posterior pituitary in response to cervix dilation + suckling
• causes trong uterine contractions
• slow IV infusion of oxytocin induces regular waves of myometrial contraction

Question 19

How is Mifepristone used to terminate pregnancy?

Answer 19

• induces labour pre-term
• progesterone receptor antagonist
• causes endometrial degeneration + sensitises uterine contractions to prostaglandins

Question 20

How is Gemeprost used to terminate pregnancy?

Answer 20

• used with Mifepristone
• ripens cervix
• helps reduce obstetric bleeding by causing vasoconstriction