Hypertension Drugs Flashcards
What does blood pressure have to be to be treated for hypertension?
160/100
or
140-159/90-99
in people with known cardiovascular disease, diabetes or organ damage
What two things must be reduced to lower blood pressure?
cardiac output ( by reducing heart rate, stroke volume, plasma volume)
and
total peripheral resistance (by dilating arteries)
How do diuretics lower BP?
- reduce plasma volume then gradually TPR
- increase sodium excretion and water follows
- reduces plasma volume
- reduce cardiac output
In brief how do vasodilators reduce BP?
directly lower TPR
In brief how do B-blockers reduced BP?
reduce cardiac output and kidney renin secretion
- bind to and block B- adrenoceptors in the heart
- block action of noradrenaline released from sympathetic nerves and circulating adrenaline
How do ACE inhibitors lower BP?
inhibit endogenous vasoconstrictor production
- prevent conversion of angiotensin I to angiotensin II
- stimulates aldosterone secretion (which inhibits salt and water excretion )
- causes vasodilation
- reduces plasma volume
How do a-blockers reduce BP?
- reduce TPR by inhibiting noradrenaline actions
- drugs used for hypertension are selective blockers of a-adrenoceptors
- prevent vasoconstriction action of endogenous noradrenaline
How do angiotensin antagonist reduce BP?
Reduce TPR by inhibiting angiotensin action
Where do thiazide diuretics have their action?
block sodium, chloride pumps in distal convoluted tubule
Where do loop diuretics have their action?
block sodium, potassium and chloride pump in loop of Henle
Thiazide diuretics are moderately potent and reduce both systolic and diastolic pressure. What do they increase?
renin release - may counteract on blood pressure
Name 5 examples of thiazide diuretics.
derived from benzothiadiazide - chlorothiazide - hydrochlorothiazide - bendrofluazide thiazide like structures - chlorthalidone - metolazone
Examples of thiazide diuretics are chlorothiazide, hydrochlorothiazide and bendrofluazide. what are the adverse effects of these?
- more frequent urination
- low profile of side effects
high safety
Loop diuretics are very potent and no more effective than thiazides at reducing BP. Who are they reserved for?
use in patients with
- renal insufficiency
- resistant hypertension
- heart failure
What are the actions of vasodilators?
- act directly on the smooth muscle cells of arteries and arterioles
- lower intracellular calcium concentration
- cause muscle cell relaxation
- results in vasodilation
What are the actions of calcium antagonist such as dihydropyridines and benzothiazepine?
- Block calcium entry through voltage- operated calcium channels in arterial smooth muscle cells
Name some examples of the calcium channel blockers such as duhdropyridines and benzothiazepines.
dihydropyridines - nifedipine - amlodipline - nicardipine benzothiazepine -diltiazem
What are the differences between dihydropyridines such as nifedipine, amlodipine and nicardipine compared with benzothiazepines such as diltiazem ?
Dihydropyridines - highly selective for smooth muscle but affect most smooth muscle
benzothiazepine - also blocks calcium channels in conducting thissue of the heart
What are the adverse of calcium channel blockers?
- flushing
- ankle oedema
diltiazem - cardiac depression
- interaction with B-blockers
a-blockers such as doxazosin, terazosin and prazosin are relatively well tolerated but what are some of the adverse effects?
- postural hypotension (dizziness, light headed)
- possible severe hypotension after first dose
Examples of beta blockers are atenolol and metoprolol.
What are their initial and continued effect?
Initial effect - reduce rate and force of heart beat - decrease cardiac output Continued treatment - cardiac output returns to normal but BP remains low (TPR reset at lower volume )
Examples of beta blockers are atenolol and metoprolol. What are the adverse side effects of these drugs?
- cold hands
- fatigue
- can provoke asthma attack in asthmatic
- heart failure
- conduction block in heart
- may affect blood lipids
Most ACE inhibitors end in pril such as captopril, enalapril and Ramipril. What are the adverse effects of these drugs?
- dry cough
- hypotension initially, especially if given with diuretic
- these effects wear off with time
Angiotensin II receptor antagonist work by blocking the action of angiotensin II at its receptors. What are examples of these drugs?
- Losartan
- Candesartan
- Eprosartan
- Valsartan
Why are angiotensin II receptor antagonist used?
- in combination with ACE inhibitors to improve mortality and morbidity
- alternative to ACE inhibitors in intolerant patients
When choosing which drug to prescribe as suggested by pharmacology thiazide is given and if ineffective add ACE inhibitor or calcium channel blocker. B-blockers used to be first line choice. why are they not now?
- less effective at reducing risk of stroke
- more side effects
What do NICE guidelines suggest when prescribing choice of drug?
start with ACE inhibitor if under 55
- add calcium channel blocker if needed and then diuretic if further needed.
- if over 55 or black or Caribbean family start with calcium channel blocker and then add ACE if needed.
