Diuretics

Diuretics and related drugs are presented in the two video sessions. Have an overview.

 

Special Points:

Diuretics increase the rate of urine formation and decrease the blood volume, thus help in decreasing the blood pressure as well as relieving edema associated with various conditions.

The two important types of diuretics useful for their diuretic action itself are Thiazides and Loop diuretics.

  1. Thiazides and thiazide-like diuretics (Hydrochlorothiazide, Chlorothiazide etc) have an additional action of long-term, direct arteriolar dilatation and also help to decrease the blood pressure on long-term administration.
  2. Loop diuretics (Furosemide Torsemide) have comparatively a shorter action, and hence are useful in acute states to decrease the blood pressure (Hypertensive crisis/emergency) as well as to decrease the edema (Heart failure/ascites/acute pulmonary edema).
  3. Osmotic diuretics like mannitol act quickly to excrete the volume by osmotic action and also decrease the intracranial tension as well as intraocular tension, and are useful to decrease cerebral edema and in acute glaucoma. They are also useful in cases of various cases of drug overdose.
  4. Carbonic anhydrase inhibitors decrease the bicarbonate concentration, and are useful in prevention of Acute Mountain Sickness, Acute congestive glaucoma (Acetazolamide Intravenous), Chronic glaucoma and to reduce intraocular pressure in various situations (as eye drops – Brinzolamide and Dorzolamide), and sometimes in epilepsy.
  5. Potassium sparing diuretics are mainly useful to save (spare) potassium). Amiloride and triamterene help to prevent hypokalemia by other drugs/other diuretics. Spironolactone and Eplerenone are potassium sparing by their aldosterone blocking action (aldosterone antagonists). They help to prevent hypokalemia due to other drugs/loop and thiazide diuretics, and are also useful in digoxin toxicity. They are extremely valuable in management of heart failure by potassium sparing action to help prevent hypokalemia, thereby minimizing the risk of cardiac arrhythmia. More importantly, Aldosterone antagonists help in heart failure by preventing the cardiac remodeling. Aldosterone antagonists are also useful in liver cirrosis (cirrhotic edema) and nephrotic syndrome (nephrotic edema), where aldosterone levels may be high. (Heart failure, liver cirrhosis, and nephrotic syndrome are the situations of secondary hyperaldosteronism). They are also useful in Primary Hyperaldosteronism (Conn Syndrome) as well as in treatment of hirsutism (due to their anti-androgenic effects because they are competitive antagonists at testosterone receptors)

SAQ/LAQ/Viva

Compare and contrast: Loop diuretics and Thiazide diuretics

Table 1: Important comparison

Loop diuretics (high ceiling) Thiazide/Thiazide like diuretics
Furosemide, Torsemide Hydrochlorothiazide. Chlorothiazide, Chlorthalidone, Metalozone
Sodium and water excretion So, Decreased blood volume So, Decrease in blood pressure Sodium and water excretion , So, Decreased blood volume amd Decrease in blood pressure
————————————- Additional direct arteriolar dilation, leading to Decrease in blood pressure
Quick acting Slow acting
Short acting Long acting
Useful in emergencies Useful for long term effect
Used in Hypertensive crisis Used as long term antihypertensive

Table 2: Adverse effects

Loop diuretics (high ceiling) Thiazide/Thiazide like diuretics
                                              Adverse Effects
Decreased levels of Na,K,Cl,Mg – Hyponatremia, hypokalemia, hypochloremia, hypomagnesemia Decreased levels of Na,K,Cl,Mg – Hyponatremia, hypokalemia, hypochloremia, hypomagnesemia
Hypokalemic metabolic alkalosis Hypokalemic metabolic alkalosis
Decreased Calcium (Hypocalcemia)  Increased Calcium

(Hypercalcemia)

 Increased levels of Lipids, glucose, uric acid – Hyperlipidemia, Hyperglycemia, Hyperuricemia Increased levels of Lipids, glucose, uric acid – Hyperlipidemia, Hyperglycemia, Hyperuricemia
Hearing disturbances Hearing disturbances
Precipitate digoxin toxicity due to decreased K and Mg Precipitate digoxin toxicity due to decreased K and Mg
Hypotension, Hypovolemia Erectile dysfunction

TTable 3: Uses of loop and thiazide diuretics

Loop diuretics (high ceiling) Thiazide/Thiazide like diuretics
                                Uses:
-Edema (Heart failure, ascites)

-Acute pulmonary edema

-Hypertensive crisis

-Treatment of severe hypercalcemia

-Treatment of hyperkalemia

-Long term management of Hypertension

-Heart failure – for long action

-Hypercalciuria

-Urinary calcium-oxalate stones

-Diabetes insipidus

 

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