The NICE guideline on the management of primary hypertension in adults (CG127), published in August 2011, which radically changed some of the recommendations on diagnose and treatment. One of these recommendations was that calcium-channel blockers (CCBs) should be used as first-line therapy in most people aged over 55 years, and for black people of African or Caribbean family origin of any age, whilst thiazide-type diuretics are only recommended as first-line therapy if CCBs are not suitable. Furthermore, the guideline states that chlortalidone 12.5 to 25 mg once daily, and indapamide 2.5mg (or modified-release 1.5mg) once daily, are preferred to bendroflumethiazide or hydrochlorothiazide for either initial treatment or as ‘add-on’ therapy. This article in the Drug and Therapeutics Bulletin (DTB) reflects on the underlying assumptions for these recommendations.

• Data used by NICE to compare initial CCB-based therapy with initial diuretic-based therapy did not show any significant differences in overall outcome for patients; the recommendation is based on a health economic model suggesting that CCBs are more cost-effective than thiazide-type diuretics when using the lowest cost drugs in their class (amlodipine compared to bendroflumethiazide).

• The NICE decision on superiority of chlortalidone and indapamide was based on “more contemporary” trials using these drugs, and a view that the benefits seen with them are not a class effect that can be extrapolated to the cheaper bendroflumethiazide (and hydrochlorothiazide which is not available except in combination preparations in the UK).

Blood pressure reductions are similar for all of thiazide-like diuretics, and most evidence points to benefit being directly correlated to blood pressure lowering. There is no clear evidence of relative differences in benefit or harm between these drugs.

The article also notes “setting aside the pharmacoeconomic debate, the most pressing practical question, is how can chlortalidone be prescribed at the doses recommended by NICE when the only non-combination preparation currently available in the UK is chlortalidone 50mg tablets (Hygroton®)? Surely the guideline development group were aware of this.”