EXPLORING DIURETICS

Diuretics forms one of the base pillars in treating hypertension and edema. These groups of drugs increases  rate of urine flow. Based on their mechanism of action their efficacy varies. Before moving into diuretics I would recommend to revise renal physiology which will make it easier to get deeper and clear concept of mechanism of diuretics. In this section I will not go into details of each and every diuretics, I would rather try to provide concept and differentiating feature based on mechanism of action and adverse effects.

ADVERSE EFFECTS OF DIURETICS

Efficacy

Class of diuretics Example
Carbonic Anhydrase Inhibitors (CAI) WEAK Acetazolamide
Osmotic diuretics WEAK Mannitol
Loop diuretics HIGH Furosemide
Thiazide MEDIUM Hydrochlorothiazide
Potassium sparring diuretics WEAK

Amiloride (Sodium channel inhibitors)

Spironolactone (Aldosterone receptor antagonist)

Lets revise different section of nephron, (see the figure)

  1. Bowman’s capsule
  2. Proximal Convoluted Tubule (PCT)
  3. Loop of Henle (LOH), Thin descending loop
  4. Loop of Henle (LOH), Thin ascending loop
  5. Loop of Henle (LOH), Thick ascending loop
  6. Distal Convoluted Tubule (DCT)
  7. Cortical collecting tubule
  8. Medullary collecting tubule

Different drugs mention above have different sites for action, they reason why their efficacy and side effects varies from each other. Action of drugs:

Site of nephron Action of drugs
1.      Bowman’s capsule
2.      Proximal Convoluted Tubule (PCT) Carbonic Anhydrase Inhibitors
3.      Loop of Henle (LOH), Thin descending loop Osmotic diuretics acts here (Osmotic Diuretics also acts in Proximal tubule)
4.      Loop of Henle (LOH), Thin ascending loop
5.      Loop of Henle (LOH), Thick ascending loop Loop diuretics
6.      Distal Convoluted Tubule (DCT) Thiazides diuretics
7.      Cortical collecting tubule

 

Potassium sparing diuretics

Potassium sparing diuretics also acts in late distal tubule.

8.      Medullary collecting tubule

MECHANISM OF ACTION

As the normal mechanism of each section of the varies, so drugs acting on different section of nephron have different side effects, though their ultimate goal is to increase the rate of flow of urine.

Mechanism of action of these groups of drugs

  1. Carbonic Anhydrase Inhibitors

Carbonic Anhydrase Inhibitors

Acts in Proximal Convoluted Tubules

Inhibits carbonic Anhydrase

Increases excretion of NaHCO3

Increased rate of flow of urine

  1. Osmotic diuretics

Osmotic diuretics

Acts in proximal tubules and thin descending loop of Henle, thin ascending loop of Henle

Due to osmotic effect, increases excretion of water

Increased rate of flow of urine

  1. Loop diuretics

Loop diuretics

Acts in thick ascending loop of Henle

Blocks sodium, potassium, chloride co transporter

Increases sodium, potassium, chloride excretion

Increased rate of flow of urine

  1. Thiazides

Thiazides

Acts in Distal Convoluted Tubules (DCT)

Blocks sodium chloride transporter

Increased excretion of NaCI

Increased rate of flow of urine

  1. Potassium sparing diuretics (Acts in late distal tubule and collecting tubules)

They can be of two types:

  1. Sodium channel blockers
  2. Aldosterone receptor antagonists

           Sodium channel blockers

       Blocks sodium channel

             Increases sodium excretion and increases potassium retention

Increased rate of flow of urine

      Aldosterone receptor antagonists

Acts as antagonist in aldosterone receptor 

Promotes sodium and chloride excretion without concomitant potassium loss

Increased rate of flow of urine

ADVERSE EFFECTS of these groups of drugs

Side effects of Carbonic Anhydrase Inhibitors

Hyper Hypo
Apnea Potassium
Metabolic acidosis

Ataxia

Tinnitus

Side effects of Osmotic Diuretics

  Hypo
Natremia

Volemia

Fluid and electrolytes imbalance

Acidosis

Dehydration

Urinary retention

Side effects of Loop Diuretics  

Hyper Hypo
Urea

Glucose

Tension

Volemia

Magnesium

Potassium

Sodium

Calcium

Metabolic Alkalosis

Arrhythmias

Ototoxicity

Side effects of Thiazide diuretics

Hyper Hypo
Urea

Glucose

Calcium

Tension

Volemia

Potassium

Sodium

Magnesium

Metabolic Alkalosis

Azotemia

Side effects of Potassium sparing diuretics

Hyper Hypo
Potassium Sodium
Metabolic Acidosis

Gynecomastia

Impotence

ADVERSE EFFECTS OF DIURETICS

Note:

Hyper Sodium: Hypernatremia

Hyper Potassium: Hyperkalemia

There are many more side effects, and more detailed mechanism of action, but it is important to have base concept before moving details of each drugs.

HAPPY READING.

If you find it fruitful, do not hesitate to share the information in your friends circle.

 

 

Dr Bivek Singh

Academic coordinator (MBBS)

Author “A journey into the human body”

Author “Pharmacology Simplified”

Board of Directors (Medical Outreach Nepal, USA)

biveksingh@hotmail.com

www.facebook.com/drbiveksingh

 

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