Blood pressure Hypertension is an independent risk factor for both microvascular and macrovascular disease in people with diabetes. The risk of CVD death progressively increases with rising systolic blood pressure, while each 10mm Hg reduction in systolic blood pressure with treatment is associated with a 15% reduction in the risk of CVD death over 10 years. Non-pharmacological measures including weight reduction, restriction of dietary salt and increased physical activity should be implemented. Most patients will require drug therapy, and many will require more than one drug to reach target BP levels. In the UKPDS 29% of patients required three or more agents to reach target blood pressure levels. It should then be spilt into the following links: Measuring blood pressure Thresholds for treatment Target blood pressure levels Choice of antihypertensive drug Notes on specific antihypertensive drugs Measuring blood pressure Blood pressure should be measured using a validated spygmomanometer according to the BHS guidelines for BP measurement (http://www.hyp.ac.uk/bhs/). Most of the evidence for treatment and target blood pressure levels has been obtained using clinic blood pressure readings. Ambulatory blood pressure measurement is therefore of limited use in most patients. Absence of a nocturnal blood pressure dip may suggest autonomic dysfunction or secondary hypertension. Thresholds for treatment Treatment should be considered in all patients with a sustained (e.g. 3 readings over two months) systolic or diastolic blood pressure greater than 140/85 mm Hg. [Below the age of 45 initiation of treatment should be considered at lower thresholds approximating to the 75th centile (see Appendix 7), taking account of retinopathy, microalbuminuria and risk factors for cardiovascular disease.] Target blood pressure levels Target blood pressure in patients with diabetes should be less than 140/80 mm Hg There is some evidence that in certain groups e.g. age under 45, those with microalbuminuria or proteinuria, lower blood pressure targets may be appropriate. Refer to Section 19.3. Choice of antihypertensive drug The most important issue is to obtain adequate blood pressure control, with a minimum of adverse effects. Type 1 patients: ACE inhibitors should be considered as first line agents. For patients unable to tolerate ACE inhibitors, an angiotensin II antagonist should be used. A variety of other antihypertensive agents can be used in addition if required. Type 2 patients: Assessment of the patient and risk of adverse events will guide choice of therapy. Low dose thiazides are the usual first choice. ACE inhibitors should be considered as first line therapy in patients with microalbuminuria with AIIA for those intolerant of ACEI. Thiazides, beta-blockers, ACE inhibitors, calcium channel blockers and angiotensin II antagonists (AIIAs) are all effective in lowering blood pressure and reducing the risk of vascular events. Notes on specific antihypertensive drugs ACE inhibitors Agent of first choice in Type 1 patients, and Type 2 patients with microalbuminuria or proteinuria. Serum creatinine and electrolytes should be measured before and one to two weeks after initiation of therapy, and after each dosage increment. An increase of creatinine of 10% can be expected, but larger increases would need reconsideration of the dose, further investigation and/or specialist advice on further assessment. An elevated serum creatinine is not an absolute contraindication to the use of ACE inhibitors. These patients should have further investigation and/or specialist advice prior to initiation of these agents. Potassium-sparing diuretics (e.g. amiloride, co-amilofruse) should normally be discontinued when an ACE inhibitor is introduced. The risk of underlying renal artery stenosis should be considered, particularly in patients with peripheral arterial disease and renal impairment. ACE inhibitors are contraindicated in pregnancy. Women of child-bearing age should be advised of this prior to commencement of treatment, and should practice effective contraception. The drug should be withdrawn prior to planned conception, or immediately in the event of a confirmed pregnancy. Angiotensin II antagonists The points raised under ACE inhibitors also apply to these drugs. AIIAs should be reserved for patients unable to tolerate ACE inhibitors (mostly due to cough). AIIAs have been shown to be effective in preventing progression of renal disease in patients with Type 2 diabetes. They are as effective as beta-blockers in the prevention of cardiovascular events, and may be more effective at preventing cerebrovascular events. For patients who have difficulty reaching BP targets, and who have normal renal function, the combination of ACE and AIIA may offer additional benefits. This should only be considered with close monitoring of renal function and BP response. Diuretics Agent of first choice in type 2 patients without microalbuminuria or proteinuria. The ALLHAT study (www.allhat.org) confirms that thiazides are effective antihypertensives in subjects with diabetes, and should be considered as first line agents in Type 2 diabetes. Low dose thiazides (e.g. bendrofluazide 2.5mg) do not cause clinically significant adverse metabolic effects. Thiazides potentiate the effect of ACE inhibitors, and thus are effective in combination. Beta blockers Diabetic patients with ischaemic heart disease will benefit from beta blocker therapy. In the UKPDS atenolol was at least as effective as an ACE inhibitor (captopril) in both blood pressure control and prevention of diabetic complications, although less well tolerated. Non-cardioselective beta-blockers should be avoided. Cardioselective beta-blockers do not affect awareness of, or recovery from, hypoglycaemia. Caution is required in patients with peripheral vascular disease and airways disease. Calcium channel blockers Long acting, once daily, calcium channel blockers are safe and effective in diabetes. There is some concern over the safety of shorter acting agents, which should not be used. Alpha blockers Doxazosin is the recommended agent in this class as the risk of postural hypotension is low. The ALLHAT study showed an increased incidence of hospitalisation due to heart failure in patients taking doxazosin compared to those taking a thiazide. This drug should be avoided in patients with compromised left ventricular function or those thought to be at high risk of developing heart failure. Centrally acting drugs Methyldopa is the antihypertensive of choice prior to and during pregnancy. Moxonidine can be used as an ‘add on’ therapy when other therapies have not achieved target pressures.