Flashcards in Anti-hypertensives 1 Deck (21)
How is systemic hypertension defined ?
> or equal to 140/90mmHg
What are the causes of systemic hypertension ?
Specific causes- renal artery stenosis, phaeochromocytoma
Essential causes - no obvious cause
How is pulmonary hypertension defined ?
Mean pulmonary artery pressure > or equal to 25mmhg
How do you calculate mean pulmonary artery pressure ?
CO * pulmonary vascular resistance + pulmonary venous pressure(left atrial pressure)
What are the causes of pulmonary hypertension ?
Arteries carrying blood from heart to lungs narrow
Specific causes - liver disease, lung disease and congenital heart abnormalities
Idiopathic causes- rare
What diseases can hypertension lead to?
Stroke , renal failure and heart failure
What are the 2 methods used to treat hypertension ?
Change in lifestyle
Pharmacological intervention - this has to be used if it's too high
How does fluid volume at renal distal tubules affect blood pressure ?
At the renal distal tubules sodium reabsorption can occur by sodium-chloride co transporter
- causes rebsoprtion of water which increases blood volume
- sodium also reabsorbed by sodium channels which are up regulated by release of aldosterone
Aldosterone binds to kidney cells causing increased transcription and increased expression off sodium channels so more sodium is absorbed
What drugs modulate the reabsorption of sodium at the kidney and how do they work ?
Thiazides diuretics - bendrofluemethiazide and aldosterone antagonists - spironolactone
Thiazides block sodium-chloride transporter to reduce reabsorption
Aldosterone antagonists block sodium channel synthesis so less sodium reabsorbed
How does the renin-angiotensin system affect blood pressure ?
Renin is released from juxtaglomerular cells and causes conversion of angiotensinogen into angiotensin 1 and then ACE causes angiotensin 1 to be converted to angiotensin 2
Angiotensin -2 causes vasoconstriction, vascular hyper trophy and sodium retention
What drugs modulate the renin-angiotensin system ?
ACE inhibitors- captopril and AT-1 receptor antagonists - candesartan
Reduce vasoconstriction, vascular hypertropy and sodium retention
How does voltage gated calcium channels contribute to blood pressure ?
Calcium channels open causes calcium to enter cell causing contraction leading to vasoconstriction b if potassium channels are open then they push the membrane potential further from threshold helping to close calcium channels
How do drugs modulate calcium channels ?
Calcium channel blockers - minoxidil
Potassium channel openers - amlodipine
They promote vasodilation by reducing calcium influx.
How does the sympathetic nervous system affect blood pressure ?
Alpha receptor- in vascular smooth muscle NA causes vasoconstriction
Beta receptor- in juxtaglomerular cells and cardiac muscle, NA increases CO and increases renin release
What drugs modulate sympathetic nervous system and how do they work ?
Alpha- blockers -doxazosin
Beta- blockers- propranolol and bisoprolol
Block vasoconstriction and reduce increase in CO and renin release
How does NO and cGMP affect blood pressure ?
NO converges guanyl Cyclase into cGMP to increas e protein kinase g
Pkg increase potassium efflux and activates myosin light chain phosphatase causing vasodilation
What drugs modulate NO activity ?
Nitric oxide donors- sodium nitroprusside- increase cGMP
Phosphoritesterase inhibitors - sildenafil - prevent degradation of cGMP
How does endothelin-1 affect blood pressure ?
Peptide releases due to trauma
Bind to et-a receptors to cause vasoconstriction
What drugs modulate the endothelin-1 mechanis my ?
ECE inhibitor - phosphoramiden - prevent production of et-1 so prevents vasoconstriction
Et-a receptor antagonists- bosentan - blocking vasoconstriction
How do prostanoids affect blood pressure ?
They binds to ip receptors increasing cAMP causing vasodilation