MSI_000025346

Methyclothiazide is only found in individuals that have used or taken this drug. It is a thiazide diuretic with properties similar to those of hydrochlorothiazide. (From Martindale, The Extra Pharmacopoeia, 30th ed, p825)Methyclothiazide appears to block the active reabsorption of chloride and possibly sodium in the ascending loop of Henle, altering electrolyte transfer in the proximal tubule. This results in excretion of sodium, chloride, and water and, hence, diuresis. As a diuretic, methyclothiazide inhibits active chloride reabsorption at the early distal tubule via the Na-Cl cotransporter, resulting in an increase in the excretion of sodium, chloride, and water. Thiazides like methyclothiazide also inhibit sodium ion transport across the renal tubular epithelium through binding to the thiazide sensitive sodium-chloride transporter. This results in an increase in potassium excretion via the sodium-potassium exchange mechanism. The antihypertensive mechanism of methyclothiazide is less well understood although it may be mediated through its action on carbonic anhydrases in the smooth muscle or through its action on the large-conductance calcium-activated potassium (KCa) channel, also found in the smooth muscle. C - Cardiovascular system > C03 - Diuretics > C03A - Low-ceiling diuretics, thiazides > C03AA - Thiazides, plain D045283 - Natriuretic Agents > D004232 - Diuretics > D049993 - Sodium Chloride Symporter Inhibitors C78275 - Agent Affecting Blood or Body Fluid > C448 - Diuretic > C49185 - Thiazide Diuretic D002317 - Cardiovascular Agents > D045283 - Natriuretic Agents D049990 - Membrane Transport Modulators