It combines with pyrophosphate in the body to form a coenzyme, participates in the oxidative decarboxylation reaction of pyruvate and α-ketoglutaric acid in sugar metabolism, and is necessary for sugar metabolism. When it is deficient, oxidation is blocked to form pyruvate, lactic acid accumulates, and affects the body's energy supply. Its symptoms are mainly manifested in the nervous and cardiovascular systems, and multiple peripheral neuritis affecting both sensory nerves and motor nerves occurs, manifested as paresthesia, neuralgia, limb weakness, and muscle soreness and atrophy. In terms of cardiovascular, due to the increase of acetone and lactic acid in the blood, the small arteries are dilated, the diastolic pressure is reduced, and the myocardial metabolism is disturbed, so it is easy to have symptoms of heart failure such as palpitations, shortness of breath, chest tightness, cardiac hypertrophy, liver and lung congestion and peripheral edema. In terms of the digestive tract, it is manifested as weakness and weight loss caused by decreased appetite.

1. Effect on water and electrolyte excretion: It can increase the excretion of water, sodium, chloride, potassium, calcium, magnesium, phosphorus, etc.; mainly by inhibiting the active reabsorption of NaCl by the thick-walled segment of the renal tubular loop, reducing the reabsorption of Na+ and Cl-, promoting the secretion of K+ by the distal tubule, and increasing the excretion of Ca2+ and Mg2+. Short-term medication can increase uric acid excretion, while long-term medication can cause hyperuricemia. 2. Effect on hemodynamics: Furosemide can inhibit the activity of prostaglandin degrading enzymes, increase the content of prostaglandin E2, and has a vasodilatory effect; dilate renal blood vessels, reduce renal vascular resistance, and increase renal blood flow; it is helpful for the treatment of acute left heart failure and provides a theoretical basis for the treatment of adult respiratory distress syndrome.

It selectively excites the medullary respiratory center and can also act on the carotid body and aortic body chemoreceptors to reflexively excite the respiratory center and increase the respiratory center's sensitivity to carbon dioxide, deepening and accelerating breathing. It has a weak excitatory effect on the vasomotor center. Excessive doses can cause convulsions.