Oral Contraceptives

Oral Contraceptives:
Used to prevent fertility by increasing dose of oestrogen and/or progesterone to create a negative feedback on hypothalamic-pituitary axis  prevents the release of FSH and LH

Combination oral contraceptives:
• combine both oestrogen and progesterone
• nearly 100% effective; safe, but with common relatively minor side effects
• action is by inhibition of ovulation; thickening of the cervical mucous  barrier for passage of sperm; and also modifies the endometrium so its less favourable for implantation
• three types – monophasic (daily amounts of oestrogen and progesterone constant amount throughout cycle); biphasic (oestrogen dose is constant, progesterone increased during second half of cycle); triphasic (progesterone dose changes at each phase of cycle)
• adverse effects – increased risk for venous and arterial thromboembolism; hypertension; abnormal uterine bleeding
• contraindicated – during pregnancy; history of thromboembolism; ischaemic vascular disease

Progesterone only oral contraceptives (minipills’):
• do not increase risk fro thromboembolism and are safer
• but, less effective as a contraceptive and can cause menstrual irregularities
• mechanism is by altering cervical secretions so they act as a barrier to penetration by sperm

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