Spironolactone
Spironolactone blocks the action of aldosterone in the kidney, so sodium and water are lost while potassium is held back rather than excreted. It also blocks androgen receptors. It is used for oedema, heart failure, high blood pressure, and androgen-driven skin problems.
It is taken with food, which improves how much is absorbed and is easier on the stomach. Because it retains potassium, the level can climb too high, especially alongside lisinopril, enalapril or losartan, or with potassium and magnesium aspartate supplements and salt substitutes; those combinations are not necessarily wrong, but they are the reason blood is checked. Potassium, sodium, creatinine and eGFR are monitored, and impaired kidney function makes a rise in potassium far more likely.
See a doctor for muscle weakness, numbness or tingling, a slow or irregular heartbeat, or a fall in the amount of urine passed. Breast tenderness or swelling and menstrual changes are also worth reporting.
Reference information, not medical advice. Discuss any change with your doctor.