Antihypertensives Lecture 10 Flashcards
Describe blood pressure maintenance
Baroreceptor reflex - mearues BP and can bring about changes in cardiovascular ways
Autonomic nervous system - fast adjustments, affects heartand vessels
RAAS- kidneys alter blood volume (slow), angiotensin 2 vasoconstricts (fast)
What is hypertension defined as and how is blood pressure normaly maintained?
-Pressure above 140/90mmHg - most common cardiovascualr disease
BP maintenance:
- Baroreceptor reflex
- RAAS
To treat hypertension - change lifestyle or use drugs to decrease CO and TPR
Describe beta adrenoceptor antagonists as antihypertensives
Act on the periphery
eg Propranolol (beta1&2) and atenalol (beta1)
Decreases HR and contractility to reduce CO
Decrease renin secretion which decreases angiotensin 2 and therefore TPR/CO
Side effects - bronchospasm on beta2 receptors amd exercise intolerance
Used in mild hypertension
Other side effects in some patients after decades of use
Describe alpha1 adrenoceptor antagonists as antihypertensives
Act on the periphery
eg Prazosin and doxazosin
Blocks vasoconstriction
SE- postural hypotension- no Baroreceptor reflex
Describe alpha 2 adrenoceptor agonists as antihypertensives
Act centrally
eg Clonidine amd methyldopa
Bind presynaptically in brain and give negative feedback to reduce NA release
Decrease sympathetic outflow bodywide and vascular tone
SE- postural hypotension, increased secretion because of unopposed parasympathetic action Drowsiness and depression Largely obsolete
Describe ACE inhibitors as antihypertensives
Targets RAAS
Angiotensin-converting enzyme inhibitors (ACE)
eg Captopril, enalapril
Decreases angiotensin 2 - lowers TPR/CO
Decreases degradation of vasodilator kinins
SE- dry coughs- kinins irrate neurones in the respiratory system First dose hypotension Used in mild hypertension
Describe the use of angiotensin 2 receptor antagonists
Targets RAAS
eg Losartan and irbesartan
Blocks AT1 receptors decreases action of angiotensin 2 to decrease TPR
No major side effects Used in mild hypertension
Describe the use of direct vasodilators as antihypertensives
Bind selectively to vascular smooth muscle
Minoxidil- severe, nitrates- severe, DHPs- mild
Describe the use of diuretics as antihypertensives
eg Thiazides, fursemide, spironolactone
Initially increase water excretion from kidney and decreases blood volume and CO. Vasodilation due to decrease in cellular Ca2+
Long term effects area atrial dilation and Na depletion- decreases intracellular Ca in vascular smooth muscle
SE- hypokalaemia
Used in mild hypertension
How are drugs combined
Combine drugs that have a direct effect on RAAS with drugs that no effect on RAAS
eg ACE inhibitors with Ca blockers/Diruetics
eg Beta blockers with Ca blockers/Diruetics
How would you treat hypotension?
Only if life threatening
Sympathomimetics- adrenaline to increase TPR/CO
