NICE published guidelines in 2006, revised in 2011.
Step 1 : Choose either an ACE inhibitor, a thiazide diuretic or a calcium channel antagonist (A, D and C).
An ACE inhibitor is more effective as first-line therapy in younger patients (< 55 years ) and Caucasians.
Diuretics or calcium channel blockers are better in older patients and African / Caribbean patients of any age.
This trial of step 1 is run on for 4 weeks, and if blood pressure is not controlled, the opposite agent is added in:
Step 2 : An ACE inhibitor is added to a diuretic (A + D) or calcium channel antagonist (A + C), or vice versa.
Step 3 : Ongoing poor control is then managed by the addition of the third agent (A + C + D).
Step 4 : If a patient is established on triple therapy, and still not well controlled, they are probably aldosterone sensitive, so spironalactone would be a wise option.
National Institute for Health and Clinical Excellence. Hypertension: Clinical Management of Primary Hypertension in Adults. NICE Clinical Guideline 127, August 2011.