Final answer:
Spironolactone promotes sodium and chloride excretion through its antagonistic action on aldosterone, which usually reabsorbs sodium and water while excreting potassium. Unlike other diuretics, it conserves potassium, making it useful for treating ascites in liver failure without depleting potassium.
Step-by-step explanation:
The pharmacological effects of spironolactone in a patient with liver failure and ascites include promoting the excretion of sodium and chloride. Spironolactone is a diuretic that works by blocking the effects of the hormone aldosterone, which normally promotes the reabsorption of sodium and water into the bloodstream while excreting potassium. Since spironolactone inhibits aldosterone's action, it leads to enhanced excretion of sodium and chloride, thereby reducing water retention in tissues and alleviating ascites. This also means that, unlike other diuretics, spironolactone does not deplete potassium reserves but rather can help to conserve them. Consequently, the correct answer to the effects of spironolactone would be D: Promotes sodium and chloride excretion.