Drugs used to treat hypertension Flashcards
Name the types of drugs used to treat hypertension and briefly state there actions?
- Diuretics = Reduce plasma volume then gradually TPR
- Vasodilators = Directly lower TPR
- A-blockers = Reduce TPR by inhibiting noradrenaline action
- B-blockers = Reduce cardiac output & kidney renin secretion
- ACE inhibitors = Inhibit endogenous vasoconstrictor production
- Angiotensin antag = Reduce TPR by inhibiting angiotensin action
How do diuretics work? what are the sites of action?
They work by increasing Na+ excretion this reduces salt re-absorption from glomerular filtrate. This causes water loss follows which reduces plasma volume resulting in reduce cardiac output
Thiazide diuretics or Loop diuretics
What are thiazides? How do they work?
They are moderately potent diuretics
• reduce systolic and diastolic pressure
• widely used antihypertensive, suitable for most patients • inhibit Na+ ,Cl- co-transport in distal tubule
• additional vasodilator action – mechanism not known
• potentiate effects of other antihypertensives
• increase renin release – may counteract effects on blood pressure
Name thiazides drugs? They end in ZIDE coz they are well snide
chlorothiazide
hydrochlorothiazide
bendrofluazide
Side effects of thiazides?
more frequent urination but high safety low profile of side effects
Loop diuretics
They are very potent diuretics
• no more effective than thiazides at reducing BP
• reserved for use in patients with renal insufficiency, resistant hypertension or heart failure
What are vasodilators? How do they work?
- Actions = act directly on the smooth muscle cells of arteries and arterioles. They lower the intracellular calcium concentration and cause muscle cell relaxation which results in vasodilation
- Calcium anatagonists most popular, A blockers and antagonists also used but less often
What is the mode of action of Calcium Antagonist?
Block Ca2+ entry through voltage-operated calcium channels in arterial smooth muscle cells
Dihydropyridines
Calcium antagonist
Highly selective for smooth muscle but affect most smooth muscle
Nifedipine and amlodipine
Calcium antagonist
Longer than dihydropyridines acting given once daily dose
Nicardipine
Calcium antagonist
Some selectivity for cerebral & coronary arteries
Benzothiazepine and diltiazem
Also block calcium channels in conducting tissue of the heart slows heart rate potentiates b-blocker action
Calcium antagonist side effects?
All cause flushing and ankle oedema, only diltiazem causescardiac depression and interaction with b-blockers
What are A-blockers? How do they work?
Its OSIN to block A
- drugs used for hypertension are selective blockers of a1 -adrenoceptors
- prevent vasoconstrictor action of endogenous noradrenaline
Name examples of A-blockers?
Doxazosin: once daily
Terazosin: once daily
Prazosin: shorter acting, 3x daily
Side effects of A blockers?
postural hypotension such as dizziness
light headedness
possible severe hypotension after first dose but generally well tolerated
What are B-blockers? How do they work?
LOL everyone laughs at ugly betty blocking the way
Bind to and block b1 -adrenoceptors in the heart (sino atrial node + ventricular muscle), they also block the action of noradrenaline released from sympathetic nerves and circulating adrenaline
Name examples of B-blockers?
Atenolol and metoprolol
Effects of B-blockers?
- initial effect – reduce rate and force of heart beat – decrease cardiac output
- after continued treatment – CO returns to normal but BP remains low and TPR “reset” at lower level
Side effects of B-blockers?
- Common side effects = cold hands and fatigue
- Less common but serious it can provoke asthma attack in asthmatic, heart failure, conduction block in heart, may also affect blood lipids
What are ACE inhibitors? How do they work?
ACE IS A PRIL
- Action = prevent conversion of angiotensin I to angiotensin II it is a potent vasoconstrictor that stimulates aldosterone secretion which inhibits salt and H2O excretion which cause vasodilation and reduce plasma volume
Name examples of ACE inhibitors?
- captopril – 2x daily dose
- enalapril – single daily dose
- lisinopril – lysine analogue of enalapril
- ramipril – single daily dose
Side effects of ACE inhibitors?
dry cough
hypotension initially, especially if given with a diuretic these effects usually wear off with time
What are Angiotensin antag? How do they work? What is there use?
SARTAN LIKE SPARTAN BUT SHITTER
- Action = Block the action of angiotensin II at its receptors it competes for binding to AT receptors
- Use = in combination with ACE inhibitor improved mortality and morbidity vs. ACEI alone also alternative to ACE inhibitor in intolerant patients
Name examples of Angiotensin antag?
- losartan
- candesartan
- eprosartan
- valsartan
Drug choice?
- thiazide – effective, safe history and few side effects
- if thiazide ineffective – add ACE inhibitor or calcium antagonist
- b-blockers were once first line choice, but – less effective at reducing risk of stroke – more side effects
