Antihypertensives Flashcards
What are the main aims of Antihypertensive drugs?
Reduce BP, Provide 24 hours control (one dose a day - long plasma half life), show dose-effect relationship and have acceptable side effects.
How do Diuretics work in controlling BP?
Act on the kidney to increase diuresis.
Increase sodium excretion, Reduce salt re-absorption and plasma volume, causing water loss.
How do Thiazides work in controlling BP?
Inhibit sodium chloride co-transport in distal tube.
Increase renin and have a vasodilator action.
Examples of Thiazides…
Chlorothiazide Hydrochlorothiazide Bendrofluazide Benzothiadiazine Chlorthialidone Metolazone
What are Loop Diuretics used for?
Renal insufficiency
Resistant Hypertension
Heart Failure
How do Vasodilators control BP?
Act on smooth muscle cells of arteries/arterioles by lowering intracellular calcium concentration to allow muscle cell relaxation.
Mechanism of Calcium Antagonists…
Block calcium entry though voltage-operated calcium channels in arterial smooth muscle cells.
Examples of Calcium Antagonists…
Dihydropyridines - smooth muscle selective (Nifedipine/Amlodipine - long acting, Nicardipine - cerebral/coronory arteries)
Benzothiazepine - block calcium channels in conducting heart tissue (Diltiazem, potentiates Blocker action)
Side Effects of Calcium Antagonists…
Flushing, Ankle oedema, Cardiac depression and Bblocker interaction.
Mechanism of Alpha Blockers…
Selective blockers of A1-adrenoceptors that prevent vasoconstrictor action of endogenous noradrenaline.
Examples of Alpha Blockers
Doxazosin, Terazosin and Prozosin (short acting).
Side Effects of Alpha Blockers…
Postural hypotension and severe hypertension after 1st dose.
Mechanism of Beta Blockers…
Bind to and block B1-adrenoceptors in the heart (sino atrial node/ventricular muscle), blocking noradrenaline action, released from sympathetic nerves/circulating adrenaline and reducing rate/force of heart beat/cardiac output.
Examples of Beta Blockers…
Atenolol/Metoprolol
Side Effects of Beta Blockers…
Cold hands, fatigue, provoke asthma, heart failure, conduction heart blood and effect blood lipids.
Mechanism of ACE Inhibitors…
Prevent conversion of angiotensin I to angiotensin II. Potent vasoconstrictor that stimulates aldosterone secretion, inhibiting H20/salt extortion to reduce plasma volume.
Examples of ACE Inhibitors…
Catopril, Enalapril, Lisinopril and Ramipril.
Side Effects of ACE Inhibitors…
Dry cough, hypotension initially when given with a diuretic.
Mechanism of Angiotensin II Receptor Antagonists…
Block the action of angiotensin II at its receptors, competing for binding to AT receptors.
Used with Ace inhibitors to improve mortality/morbidity.
Examples of Angiotensin II Receptor Antagonists…
Losartan, Candesartan, Eprosartan and Valsartan.
What effects choice in drug to use?
Patient Characteristics
Effectiveness at lowering BP
Complications / Adverse effects
Cost Effectiveness
