Quinethazone is an oral thiazide-like diuretic drug that acts in the kidney, specifically in the distal convoluted tubule of the nephron. It is used in the treatment of hypertension. In the distal convoluted tubule (DCT), the regulation of ions such as sodium, potassium, calcium, chloride, and magnesium occurs. In epithelial cells of the DCT, the basolateral membrane consists of the Na+/K+ ATPase, which pumps Na+ into the interstitium-blood area and K+ into the epithelial cell; the Na+/Ca2+ exchanger, which pumps Na+ into the cell and Ca2+ into the interstitium-blood; and the chloride transporter which transports chloride into the interstitium-blood. The apical membrane contains a calcium channel that transports calcium from the lumen into the epithelial cell, a potassium channel that transports K+ out of the epithelial cell, and a Na+/Cl- cotransporter which transports Na+ and Cl- into the epithelial cell. Quinethazone targets this Na+/Cl- cotransporter. Quinethazone is transported from the blood into the epithelial cells. In the cell, it has access to the Na+/Cl- transporter and inhibits it preventing Na+ and Cl- reabsorption. The inhibition of Na+ reabsorption results in a low cytosolic concentration of Na+ and increases the solute concentration of the lumen. This decreases the lumen-epithelial cell concentration gradient and as a result, less water would be reabsorbed from the urine. This effect is valued in conditions such as hypertension because it allows more water to be excreted in the urine rather than be absorbed in the blood which increases blood volume. Since less Na+ is available for the Na+/K+ ATPase function, K+ accumulates in the cell and the ATP-sensitive inward rectifier potassium channel(IKATP) transports this excess K+ into the lumen, thus increasing K+ excretion. Side effects such as nausea, dizziness, hypokalemia, and dry mouth can occur from taking Quinethazone. This drug is administered as an oral tablet.

Quinethazone Pathway References