antihypertensives Flashcards
basic approach for antihypertensive therapy
Controlling weight by diet and exercise
Smoking cessation
Decreasing alcohol intake
Decreasing sodium intake
Exercising on regular basis
Resting and avoiding stress
Environmental factors further predispose an individual to the occurrence of hypertension:
Stressful lifestyle,
High dietary intake of sodium
Smoking
what is blood pressure directly proportional to
CO AND PR
what are the two control mechanisms in turn that regular CO and PR
the baroreceptors mediated by the sympathetic nervous system (QUICK RESPONSE)
the renin angiotensin aldosterone system (SLOW RESPONSE)
antihypertensives work to reduce and decrease what?
reduce CO and decrease PR
where are baroreceptors located and what are they sensitive to
in blood vessels
changes in blood pressure
explain reduction in BP to increase in BP with baroreceptors and the sympathetic nervous system
QUICK RESPONSE
fall in BP = baroreceptors send fewer messages to cardiovascular centres in CNS
results in increased sympathetic activity output to heart and blood vessels
results in vasoconstriction and increased cardiac output
so increase in BP
explain the renin-angiotensin-aldoesterone system (RAAS)
aldosterone stimulates sodium and water reabsorption in the kidney, increases blood volume, increases cardiac output and increase in BP
what do baroreceptors in the kidney respond to reduced BP by releasing
an enzyme called renin
what is renin responsible for the production of
angiotensin I
what is Angiotensin I, converted in turn to Angiotensin II by?
angiotensin converting enzyme (ACE)
what stimulates aldosterone production
angiotensin II
give 9 classes of antihypertensive drugs
1) diuretics, thiazides
2) beta adreno-receptor blocking agents
3) ACE inhibitors
4) Angiotensin-II Receptor Antagonists
5) renin inhibitors
6) centrally acting antihypertensive drugs
7) vasodilators
8) alpha adrenoreceptor blocking drugs
9) calcium channel blockers
renin inhibitors
examples
how do they work
aliskiren
inhibit renin and act in the renin angiotensin aldosterone system, act early
vasodilators
examples
how do they work
hydralazine and minoxidil
produce a direct relaxation of vascular smooth muscle, resulting in vasodilation
direct effect as no innervation and not mediated by receptors
Diuretics
examples
how do they work
bendroflumethazide, benzthiazide, hydrochlorothiazide
block the distal renal tubular sodium reabsorption
so they reduce BP by reducing circulating blood volume
more water retained in kidney
longer term = reduce peripheral resistance
Beta-adrenoceptor Blocking Agents (–OLOL)
examples
how do they work
metoprolol, bisoprolol, atenolol
reduce cardiac output and reduce peripheral resistance therefore reduce blood pressure
reduce sympathetic outflow
side effects of beta adrenoreceptor blocking agents
hypotension
bradycardia
fatigue
insomnia
sexual dysfunction
Angiotensin converting enzyme (ACE) inhibitors
examples
how do they work
ramipril, Captopril
reduce BP by reducing PR
block ACE which cleaves angiotensin I to form the potent vasoconstrictior angiotensin II
which means reduced aldosterone secretion, decreased sodium and water retention
when are ace inhibits recommended
when the first line agents are contraindicated or ineffective
what are the first line antihypertensives
diuretics and beta blockers
side effects of ACE inhibitors
Dry cough, due to increased levels of bradykinin in the pulmonary tree.
Rash
Fever
Hypotension
Hyperkalemia: Potassium levels must be monitored. Also, potassium-sparing diuretics and potassium supplements are contraindicated.
Calcium channel blockers
examples
how it works
amlodipine
felodipine
interfere with vascular tone by decreasing cytosolic calcium concentration and release of Ca2+ from the sarcoplasmic reticulum (decreasing peripheral resistance)
side effects of CCB’s
Constipation occurs with verapamil.
Dihydropyridines-dizziness, headache and a feeling of fatigue caused by a decrease in blood pressure.
Avoid verapamil in patients with congestive heart failure, due to its negative inotropic effect.
a1-adrenoceptor blockers
examples
how it works
prazosin, doxazosin
block a1 adrenoreceptors to a competitive lock
decrease peripheral vascular resistance
lower BP
relaxation of arterial and venous smooth muscle
