Adrenergic Antagonists Flashcards
Alpha blocker mechanism
Blocks NA from entering Sm. Muscle -> prevents binding + contraction -> causes vasodilation and decrease in blood pressure
Non-selective alpha blockers examples + action
- Block a1 + a2 in pre-synaptic neurones
-> phentolamine (4 hours) reversible
-> phenoxybenzamine irreversible
=> more NE -> beta receptors on heart so tachycardia + arrhythmia
Selective alpha 1 blocker action + used to treat
Reversible -> vascular smooth muscle relaxation + decrease blood pressure
- hypertension + prostate issues
- > osin suffix
Alpha 1 blockers for hypertension
Prazosin
Dexuzosin
Terazosin
-> incresed specificity
Alpha 1 blockers for prostate
Tannsulosin
Alfuzosin
Silodosin
-> relaxes urinary difficult
What is physiological antagonism?
Effects of a drug are prevented by acting on different receptors which have opposite effects to receptors mediating effects of drug
Beta blocker mechanism of action
Competitive inhibitors
- > sympathetic effects
- > mainly used to treat glaucoma
1st generation beta blocker examples
Non-selective
- propranolol -> CNS -> migraine prophalaxis -> b1
- nadolol -> decrease HR, decrease contraction through AV
- tremolol -> decrease intraocular pressure -> glaucoma
=> not recommended for COPD, asthma
2nd generation beta blocker examples
Selective for b1
- suitable for chronic lung disease
- > bisoprolol
- > motoprolol
3rd generation beta blockers are
Non-selective and selective
-> also act on blood vessels -> vasodilation -> useful for hypertension
Non-selective 3rd generation beta blockers
Beta and a1 receptors
- corvedilol -> Heart failure
- labetalol
Selective 3rd generation beta blockers
B1 receptor
- nebrolol -> vasodilation -> increased NO
- betaxolol -> vasodilation -> block Ca2+ channel -> decrease intraocular pressure
What separates pindolol and acetobutolol from other blockers?
Sympathomimetic. They both block and weakly excite b1 + b2) -> diminished effect on cardiac output -> activity is useful for bradycardia
MAO - what does it do, where and what type of inhibitors inhibit MAO?
Metabolises catechloamines
- mitochondria
- inhibitors can be selective/ non selective
MAO-A inhibition is also known as the ‘cheese reaction’’. Elaborate.
Tyramine (from cheese) absorbed into sympathetic nervous system and displaces NA -> vasoconstriction on post-junctional adrenoreceptors. This increases peripheral resistance
- > dangerous because subarachnoid haemorrhage can occur in patients with pheocryotoma
- > NA metabolite urinary VMA used as diagnosis
