Oral contraceptives Flashcards
What are the two types?
Combined Oral Contraceptives (COC) or the Progestogen Only Pill (POP)
How does the Pill work?
The pill uses the body’s negative feedback system to prevent ovulation and implantation of an embryo in the same way the hormones provided by the placenta halt the female cycle during pregnancy. i.e. the pill mimics pregnancy
What is the mechanism of action of Oestrogen?
Oestrogen causes a negative feedback on the anterior pituitary, which greatly decreases the release of FSH (follicle stimulating Hormone), which prevents follicular development and helps prevent ovulation
It also enhances motility of the fallopian Tube, causing abnormal rates of ovum transport.
What is the mechanism of action of Progesterone concerning the feedback loop?
This causes a negative feedback on the Hypothalamus, greatly decreasing the release of GnRH (gonadotrophin releasing hormone) which prevents the surge of release of LH (luetinizing hormone) and FSH, preventing the release of an egg and ovulation.
What is the most important mechanism of action of progesterone in the PoP
It works on the Cervical Mucous by decreasing the amount and increase the viscosity of mucous which is hostile to sperm. It is the most important mode of action of PoP.
What are the other 2 mechanisms of action of progesterone not involving the feedback loop?
Progestogen inhibits motility of the Fallopian tube causing abnormal rates of ovum transport.
Sustained levels of Progestogen also prevents the lining of the womb - The UTERINE ENDOMETRIUM from developing properly, making it less receptive to implantation.
What is the other mechanism of Oestrogen not involving the feedback loop?
Sustained low levels of Oestrogen will prevent the lining of the womb - the UTERINE ENDOMETRIUM from developing properly, making it less receptive for implantation.
What are the hormones in the COC pill?
A synthetic Oestrogen (usually ethinylestradiol) plus a synthetic Progesterone - Progestogen.
What are the two groups of COC
Monophasic and Phasic
What is the other type of COC pill that can be either monophasic or phasic?
The ED pill - Every Day pill that has 7 placebo pills to help with compliance for women who fin it hard to know when to stop and start taking their pill.
What is the Monophasic COC pill?
Include the same dose of hormone in each pill and is taken for 21 days of the 28 day cycle.
What does the steady stream of hormones in the monophasic COC lead to?
The same level of hormone in these pills leads to a reduction in the cyclial symptoms commonly associated with hormone flunctuatuon like mood swings and bloating.
Why is there a ‘pill free break’ in the cycle of monophasic and phasic but not ED?
The 7 day break with no pill is when the thin lining of the womb sheds to mimic a period. Although there is no ‘pill free break’ with the ED pills, the pills taken at the 7 days are placebo, so have no hormones in them, therefore will still shed the womb lining during the 7 days - a period.
What is the Phasic COC pill?
The dose of the pill changes during the cycle to better emulate the natural hormonal changes in a woman’s body and are taken for 21 of the 28 day cycle.
What is the disdvantage of the Phasic COC pill, and who are these pills reserved for?
Phasic pill tends to lead to a heavier bleed during the 7 day break. They are normally reserved for women who suffer with spotting, breakthrough bleeding and irregular periods with the monophasic pills.
How many generations are there and which is most widely used and why?
3 generations based on type of Progesterone.
1st generation has more unwanted side effects.
2nd and 3rd generations are similar in effectiveness and side effects, but 2nd is much cheaper so is used more often e.g. Microgynon.
What is the standard dose of oestrogen in a normal COC pill?
The standard dose is between 30-35mcg, may be 30-40mcg in phasic pills.
When would higher doses be used and what is the maximum dose?
Higher doses may be required for women taking liver enzyme inducers. The dose would rarely exeed 50mcg.
What is the standard dose for Monophasic COC
30-35mcg oestrogen
What is the standard dose for Phasic COC
30-40mcg oestrogen
When may higher doses of oestrogen be required?
Women who are taking liver-enzyme inducers
What are the two tests taken to check eligibility and what are the levels of each when the pill wouldn’t be recommended:
Blood pressure and BMI systolic >140mmHg diastolic >90mmHg BMI >30kg/m2 risk of VTE doubles BMI >35kgm2 risk of VTE increases x4 *VTE = venous thromboembolism
What is the dose of the low dose COCs and why may these be preferred for certain women?
20mcg oestrogen.
Preferred for women with risk of CV disease and stroke due to lower risk of venous thromboembolsim
What are the risk factors for VTE (venous thromboembolism)
Family history of VTE Obesity (BMI>30, avoid >35) Long term immobilisation Over 35 (avoid >50) Smoking Avoid if 2 or more factors present
What are the risk factors for arterial disease?
Family history Diabetes Hypertension (>140/90 avoid if >160/95) Smoking Over 35 (avoid >50) Obesity (BMI >30) Migraine without aura Avoid if 2 or more present
What may be used id the risk factors don’t allow the use of normal COCs?
A low dose of oestrogen COC or a PoP.
When should oestrogen containing contraceptives be discontinued involving surgery?
4 weeks before a major elective surgery, all surgery to the legs, or surgery involving prolonged immobilisation of the lower limbs.
The risk for VTE increases by 3-5 fold with 2nd or 3rd generation COC for a healthy woman, so why are they still used?
In comparison to pregnancy, this is considered low so the benefit outweighs the risk.
When can the COC be initiated, and when does the contraceptive effect start?
The COC can be started within the first 5 days of the Menstrual cycle, and the contraceptive effect is immediate.
Or it can be initiated at another time during the cycle (but pregnancy must be excluded) and an additional barrier must be used for the first 7 days of use.
When is the critical time for a missed pill?
Start or end of the cycle and at either end of the 7 day break
What should a woman do if she forgets to take the pill?
She should take a pill as soon as she remembers, and then take the next pill at the normal time even if that means taking two together.
If 2 or more pills are missed what should happen?
The contraceptive effect is comprimised and additional contraception should be used for 7 days. Emergancy hormonal contraception may also be needed. If the 7 days runs into the pill free interval, a new pack should be started without a break.
