This is a four-week randomized controlled single blinded trial of subjects presenting with resistant hypertension in a specialized diabetes care unit of Cameroon. They are randomly assigned using the method of blocks to treatment with a daily 25mg of spironolactone or to routine intensification of antihypertensive regimen , all added to previous regimen with unchanged diet. Visits are scheduled at the start of the treatment, at weeks two and four following add-on therapy initiation. The primary outcome is change in office and self-measurement blood pressure recorded at each visit, and secondary outcomes are variations in serum potassium, sodium, and creatinine levels.

Inclusion Criteria:

• Resistant hypertension
• Diabetes mellitus

Exclusion Criteria:

• T2DM with overt acute/chronic complications,
• serum potassium ≥ 5.5 mmol/l,
• estimated Glomerular Filtration Rate (eGFR) calculated using the Modification of Diet in Renal Disease formula ≤ 30 ml/min/1.73m² of body weight,
• absolute contraindication to any of the drug regimen of the trial,
• and current aldosterone antagonist treatment or cessation within the last 15 months