Thiazide and thiazide-like diuretics

Diuretics are medications that act on the kidneys to increase production of urine, therefore elimination of water from the body.

There are 5 main types of diuretics - carbonic anhydrase inhibitors, osmotic diuretics, loop diuretics, potassium sparing diuretics, and last but not least, thiazide and thiazide-like diuretics - which we’ll get intimately acquainted with during this video.

Now, the basic unit of the kidney is called a nephron, and each nephron is made up of a glomerulus, which filters the blood. The filtered content goes through the renal tubule, where excess waste and molecules, such as ions and water, are removed or filtered through an exchange between the tubule and the peritubular capillaries.

So the renal tubule plays a huge role in secretion and reabsorption of fluid and ions - such as sodium, potassium, and chloride, in order to maintain homeostasis - or the balance of fluid and ions in our body.

The renal tubule has a few segments of its own: the proximal convoluted tubule; the U-shaped loop of Henle, with a thin descending, a thin ascending, and a thick ascending limb; and finally, the distal convoluted tubule, which empties into the collecting duct, which collects the urine.

Alright, so thiazide and thiazide-like diuretics are taken perorally, and once in the blood, they travel to the kidneys where they are secreted by the proximal convoluted tubule into the lumen of the renal tubule.

An important point to make here is that they are secreted by the same secretory system that secretes uric acid into the tubule, so they compete with the secretion of uric acid, therefore increasing uric acid levels in the blood.

Next, they travel along with the filtrate until they reach the distal convoluted tubule. This part of the nephron is lined by epithelial cells.

Now, on the luminal side of these cells, there’s a nifty little sodium-chloride transporter. This channel reabsorbs one sodium and one chloride ion together from the tubule, into the cell. Sodium is reabsorbed along with water into the interstitium, and then into the bloodstream.