antihypertension drugs Flashcards
Give some examples of thiazides
Hydrochlorothiazide
Bendroflumethiazide
How do thiazides function
Blocking the Na+/Cl- symporter in the first part of the Distal convoluted tubule
As less Na+ is absorbed, less water will be reabsorbed leading to diuresis and decreased blood volume and consequential decreased BP
They also have vasodilator action
side effects of thiazides
Electrolyte disturbances
Decreased glucose tolerance
Can reduce efficacy of anticoagulants and uricosurics
Can increase LDL and cholestrol
Give examples of drugs that are calcium channel blockers
Nifedipine
Amlodipine
What is the mechanism of the calcium channel blockers
Dilate peripheral vessels so that:
- Reduced peripheral resistance
- Reduced filling pressure
What are the side effects of calcium channel blockers
Peripheral oedema
Dizziness
Give some examples of angiotensin converting enzyme (ACE) inhibitors
Catopril
Enalapril
What is the mechanism of action of the ACE inhibitors
Angiotensin II is a powerful vasoconstrictor normally and activates aldosterone which stimulates thirst and water retention
ACE inhibitors block the conversion of angiotensin I to angiotensin II thus having 2 effects
1) Rapid anti-ANG II effect - prevents vasoconstriction
2) slower effect by reducing blood volume and thirst
what are the side effects of ACE inhibitors
Cough in 15% - related to bradykinin
Hyperkalemia - as no K+ excretion as Na+ is not absorbed as much
Taste disturbances
First dose hypotension due to the direct anti-angiotensin II effect (prevents vasoconstriction)
What does the binding to alpha-1 adrenoreceptors cause
vasoconstriction
Give examples of drugs that block alpha-1 adrenoreceptors
Prazosin
Doxazosin
What is the mechanism of action of alpha-1 adrenoreceptor blockers
they antagonise noradrenalie which binds to the alpha-1 receptor with a higher affinity to adrenaline thus blocking vasoconstriction and thus decreasing blood pressure
Side effects of alpha-1 adrenoreceptor blockers
Headache
Nausea
Hypotension
Auto-immune problems
Give some examples of angiotensin II receptor blockers
Losartan
What is the mechanism of action of angiotensin II receptor blockers
It is an angiotensin II antagonist that blocks the AT-1 recpetor
It thus prevents water prevention and thirst causing a decrease in BP
what are the side effects of angiotensin II receptor blockers
Hyerkalemia
Diarrhea
Dizziness
Tiredness
Give some examples of K+ channel activators
Minoxidil
Pinacidl
What is the mechanism of action of K+ channel activators
As calcium entry into the smooth muscle cell depends on the membrane potential, by allowing more K+ into the cell you are hyperpolarising it and thus inhibiting L-Type Ca2+ channels and the sodium-calcium exchanger preventing vasoconstriction
side effects of K+ channel activators
Fluid retetntion
May worsen angina
Hirsuitism = increased hair growth
What is the mechanism of action of the antihypertensive drug alpha-methyldopa
It is converted to methyl-noradrenaline which is not metabolised by MAO and is stored in the synaptic vesiclesI
Its storage in the synaptic vesicles displaces noradrenalin so that when the nerve is stimulated less noradrenaline is released so there is less alpha-1 adrenoceptor activation and less vasoconstriction.
The drug also reduces renin secretion so decrease ANG II levels
When is alpha-methyldopa used
reserved for hypertension that doesnt respond to other treatments e.g. sever pre-eclampsia
Give examples of the gangion blocker drugs (old drugs)
Guanethidine
Guanadrel
What is the mechanism of action of gangion blocker drugs
They target the peripheral adrenergic neuron
Uptake leads to guanadrel substituting fro noradrenaline in secretory granules reducing sympathetic neurotransmission
When are ganglion blockers used
Reserved for uncontrollable hypertension
