Full details of the evidence and the committee's discussion are in evidence review F: step 2 and step 3 treatment. Step 4 treatment 1.4.46 If hypertension is not controlled in adults taking the optimal tolerated doses of an ACE inhibitor or an ARB plus a CCB and a thiazide-like diuretic, regard them as having resistant hypertension. [2019] 1.4.47 Before considering further treatment for a person with resistant hypertension: Confirm elevated clinic blood pressure measurements using ambulatory or home blood pressure recordings. Assess for postural hypotension. Discuss adherence (see recommendation 1.4.40). [2019] 1.4.48 For people with confirmed resistant hypertension, consider adding a fourth antihypertensive drug as step 4 treatment or seeking specialist Follow the MHRA safety advice on ACE inhibitors and angiotensin II receptor antagonists: not for use in pregnancy, how to use for breastfeeding and clarification on breastfeeding. 1.4.49 Consider further diuretic therapy with low-dose spironolactone for adults with resistant hypertension starting step 4 treatment who have a blood potassium level of 4.5 mmol/l or less. Use particular caution in people with a reduced estimated glomerular filtration rate because they have an increased risk of hyperkalaemia. [2019] In March 2019, this was an off-label use of some preparations of spironolactone. See NICE's information on prescribing medicines. 1.4.50 When using further diuretic therapy for step 4 treatment of resistant hypertension, monitor blood sodium and potassium and renal function within 1 month of starting treatment and repeat as needed thereafter. 1.4.51 Consider an alpha-blocker or beta-blocker for adults with resistant hypertension starting step 4 treatment who have a blood potassium level of more than 4.5 mmol/l. [2019] 1.4.52 If blood pressure remains uncontrolled in people with resistant hypertension taking the optimal tolerated doses of 4 drugs, seek specialist advice. 