 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. 