Final answer:
The most often used type of diuretic for treating high blood pressure, likely prescribed to your friend's grandfather, is hydrochlorothiazide, which reduces blood volume and blood pressure by increasing urine output.
Step-by-step explanation:
Your friend's grandfather has most likely been placed on a diuretic to treat hypertension. The most frequently prescribed diuretic for this purpose is hydrochlorothiazide, which works by inhibiting the Na/Cl symporter in the distal convoluted tubule and collecting duct of the nephron. This inhibition leads to reduced reabsorption of these ions and increased urine production, effectively lowering blood pressure by reducing blood volume.
Loop diuretics are another class of medication used to treat high blood pressure and they operate on the ascending limb of the loop of Henle, inhibiting the reabsorption of Na+ and Cl- ions, and also increasing urine output. Diuretics are widely used to manage conditions like congestive heart failure and fluid retention, and their side effects include increased urination due to the inhibition of water reabsorption in the kidneys.