Basics Of Pharmacy: Basics Of Diuretics

Wednesday, January 24, 2024

Basics Of Diuretics


Diuretics are substances which help to increase the urination & remove excessive fluid & salts from the body.

Diuretics also help to lower the blood pressure & are used in medical conditions which are due to excessive fluid.Diuretics are also known as water pills.

In simple words diuretics are the Drugs/medications that produce a state of high urine flow.


Normally, diuretics tend to secrete a high amount of Sodium and ions alongside water through urination. Due to this capability, they are named among the First Line of Treatment of Hypertension.

Besides this, they are used in the treatment of Cardiovascular Events (CVEs) and Edema. 

In this article we will discuss following,

  • Normal Physiology of Nephron 

  • MOA of Diuretics

  • Classification Of Diuretics 

  • Drugs MOA, Therapeutic Uses & Side Effects

  • Diuretic Resistance

  • Prevalence

  • Case study

  • Combination Therapy

  • Overall Side Effects

  • Important Points



Bowman's capsule performs the filtration of blood plasma (16%-20%) through capillaries. Filtrate buildup of glucose, electrolytes (k+, Na+, Cl-), sodium bicarbonate, and amino acids reabsorbed into the blood from the lumen.So

Regulation of 

  • urine volume


  • iconic composition 

is held by five zones of the nephron in the kidney. 

These functional zones are as follow,

  1. Proximal convoluted tubule (PCT)(67% reabsorption of Na)

  2. Descending loop of Henle 

  3. Ascending loop of Henle (25% reabsorption of Na)

  4. Distal Convoluted Tubule (DCT)(5% reabsorption of Na)

  5. Collecting Tubule and Duct (1% reabsorption of Na)

PCT and DCT are present in the cortex part of the nephron while other zones are present in the medulla.


Diuretics mechanism of action is simply prescribed as ‘the inhibition of Na and water reabsorption from the lumen to blood’


All diuretics act differently according to their mechanism.


Diuretics are divided into five categories according to different nomenclature. These drugs are more defined to act at different sites of a nephron.


  1. Loop Diuretics 

  2. Thiazide Diuretic

  3. Potassium Sparing Diuretic 

  4. Carbonic Anhydrase Inhibitor 

  5. Osmotic Diuretics                                         


Normal Physiology of Nephron

In normal physiology of nephrons at the Ascending loop of Henle 25% of Na, Cl & k are reabsorbed from lumen to blood through Na & cl ion co-transporter. 

Mechanism Of Action Of Loop Diuretics 

Loop diuretic act as to inhibit the Na, Cl & K Co transporter pump and reabsorption of these ions does not take place. 

As a result, these ions are excreted within water in large volumes of urine.

Drugs of Loop of Henle

It includes following drugs,

  1. Bumetanide

  2.  Furosemide

  3.  Torsemide 

  4. Ethacrynic acid

Therapeutic Uses

Following are therapeutic uses

  1. Edema

  2.  Hypercalcemia

  3.  Hyperkalemia

Side effects

It includes 

  1. Ototoxicity

  2.  Hypotension 

  3. Hypokalemia


Normal Physiology of Nephron

In normal physiology at distal convoluted tubules Na & Cl go into blood and Calcium into urine.

Mechanism Of Action Of THIAZIDE Dietetics 

Thiazide controls the reabsorption of Na and Cl 5% by inhibiting the pump thus increased excretion of Na & Cl occurred.These drugs also have a vasodilation effect.Calcium reabsorbed occurred by thiazide diuretics.

Drugs of Thiazide

It includes 

1.Chlorothiazide 2.Hydrochlorothizide 3.Indapamide



Therapeutic Uses

It includes 

  1. Hypertension

  2. Heart failure

  3.  Hypercalciuria

Side effects

It includes 

  1. Hypokalemia

  2. Hypomagnesemia 

  3. Hypovolemia


Normal Physiology of Nephron

In normal physiology, the carbonic anhydrase enzyme is responsible for the reabsorption of bicarbonate.These Act on the proximal convoluted tubules.

Mechanism Of Action OF Carbonic Anhydrase Inhibitors

In a drug situation, bicarbonate is not reabsorbed and is lost in the form of sodium bicarbonate from blood to urine.Hence large amounts of urine excrete.

Drugs of CAI

It includes 

  1. Acetazolamide

Therapeutic uses Of CAI

It includes

  1. Glaucoma

  2. Altitude Sickness 

Side effects

It includes

  1. Drowsiness

  2. Metabolic acidosis 

  3. Renal stone formation


Normal Physiology of Nephron

In normal physiology at collecting tubule, the reabsorption of Na along with excretion of K+ ions occurred.

MOA Of Potassium Sparing Diuretics 

Potassium-sparing diuretics act on the collecting tubule, having a strong property of antagonizing the aldosterone receptor. Thus, Na+ moves outside the body in the form of urine and K+ moves backward to blood to retain in the body.

Drugs Of Potassium Sparing Diuretics

It includes

  1. Spironolactone 

  2. Eplerenone

Therapeutic uses

It includes

1.Resistance Hypertension 2.Polycystic Ovary Syndrome 

           3.Heart failure

Side effects

It includes : 

  1. Drowsiness

  2. Metabolic acidosis 

  3. Renal stone formation


Normal Physiology of Nephron

In normal physiology, the descending loop of Henle reabsorbs the amount of Na as well as Ca+ and Mg due to high blood concentration.

Mechanism Of Action Of Osmotic Diuretics 

Osmotic diuretics act on the descending loop of Henle and prevent the reabsorption of water. Thus reduce the plasma volume also and conduct the elevated excretion of Na, K+, Mg, Ca+. Precisely, these drugs enhance the solute concentrations in the tubular lumen to retain the water in tubules.

Drugs Of Osmotic Diuretics

It includes

  1. Mannitol 

  2. Urea

Therapeutic uses

 It includes

  1. Acute Glaucoma 

  2. It helps patients with increased intracranial pressure

Side effects

 It includes

  1. Dehydration

  2.  Hyponatremia 


Diuretic resistance is defined as the inability to reduce edema even if the dose is provided to its maximal or therapeutic level. The main causes of resistance to diuretics are 

  1. Poor adherence to drug

  2. Elevated level of Na+ Reabsorption

  3. Pharmacokinetic problems 


It is estimated that between 20% and 30% of HF patients have diuretic resistance (DR).


A case study results showed that increased usage of antihypertensive drugs with diuretics causes the arousal of renal cell cancer in white people. Added to more conclusions, the elevated duration of usage of Diuretics leads to an increased risk of renal cancer cells.


Practitioners prescribed diuretics as combination therapy for treating diseases such as Hypertension and Heart Failure patients.


Side effects of diuretics may count as 

  • Stomach upset known as Indigestion 

  • Hair Loss

  • Dizziness

  • Nausea

  • Headache 

  • Muscle Cramps

  • Dehydration

  • Breast Enlargement



In a short way, some important points must be remembered related to diuretics,

  • All diuretics result in excretion of K+ except Potassium Sparring Diuretic

  • Potassium Sparring Diuretics may induce Gynecomastia

  • Furosemide (Loop Diuretic) is used only in an Emergency situation

  • Calcium Reabsorption results in the action of Thiazide Diuretics.

  • Weakest Diuretic action performed by the Carbonic Anhydrase Inhibitors

  • The most powerful action of diuretics is shown by the Loop Diuretics.

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