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• Calcium channel blockers


  Mechanism of action: Inhibit the influx of calcium ions. Act on: myocardial muscle - inhibit contractility, myocardial conducting system - inhibit formation and propagation of depolarisation, vascular smooth muscle - coronary or systemic vascular tone reduced - vasodilation
• Calcium channel blockers


  • Oral route - bioavailability 60%, half-life of amlodipine 30-50 hours, steady-state plasma concentrations - 7 to 8 days of daily dosing, liver CYP450 - slowly metabolised, renal elimination but poor renal function does not significantly reduce elimination
• ACE inhibitors


  Mechanism of action: Inhibits the angiotensin-converting enzyme in the renin-angiotensin system
• ACE inhibitor - lisinopril


  • Oral administration - 25% bioavailability, Peak plasma concentration 4-8h, half-life 12h, Water soluble - not metabolised in liver and undergoes renal excretion unchanged
• ARBs


  Mechanism of action: Selective competitive blockers of angiotensin II at the AT1 receptor
• ARB - losartan


  • Oral administration - 32% bioavailability, First-pass metabolism 14% to active metabolite which is more potent, non-competitive and longer acting, Cytochrome P450 metabolism - half-life of 2h and 3-9h for metabolite, Extensive plasma protein binding, Excreted in urine and bile
• Thiazide-like diuretics


  Mechanism of action: Inhibition of Na+ and Cl− reabsorption from the distal convoluted tubules by blocking the Na+-Cl− symporter. At lower doses vasodilatation is more prominent than diuresis
• Thiazide-like diuretics


  • Low dose sufficient for therapeutic effect, Higher doses - marked changes in plasma K+, Na+, uric acid, glucose, and lipids, Oral administration and administered early in the day so that the diuresis does not interfere with sleep, Duration of action of 12 to 24 hours
• Thiazide-like diuretic - indapamide


  • Oral administration act within 1 to 2 hours, Administered early in the day, Duration of action of 12 to 24 hours, 75% plasma protein bound
• Spironolactone


  Anti-hypertensive in patients with resistant hypertension, Blocks aldosterone-induced Na reabsorption: causes Na+ & H2O loss, K+ retention
• Alpha blockers e.g. doxazosin

  Block arterial Alpha 1 receptors, Postural Hypotension
• Beta-blockers


  Not a preferred initial therapy for hypertension, May be considered in younger people: intolerance or contraindication to ACE inhibitors and ARB's, women of child-bearing potential, evidence of increased sympathetic drive