Mechanism of action
Amiloride is an antikaliuretic with weak natriuretic, diuretic and antihypertensive effects. It exerts its potassium-sparing effect by inhibiting Na reabsorption at the distal renal tubules; this decreases the net -ve potential of the tubular lumen and reduces both K and hydrogen secretion and their subsequent excretion.
Hydrochlorothiazide is a diuretic and antihypertensive. It reduces electrolyte reabsorption from the renal tubules. It increases excretion of Na and chloride in approx equiv amounts.