Diuretics

It is good to revise on renal system so that we can understand mechanism of diuretics easily. Diagram 1 below gives an overview of the tubule transport systems and site of actions of diuretics.

Diagram 1

(RA=reabsorption)

There are two types of diuretics: 

(i) Direct action on the cell of nephron 

(ii) Indirect action

Diagram 2: classification of the diuretics

Table 1 and 2 summarises the properties of diuretics act directly on nephron.

Table 1

In the management of hypertension,

Diuretics

•Reduce BP by 10 – 15 mmHg
•Thiazides used in moderate HPT
▫Chlorothiazide, Hydrochlorothiazide,Bendroflumethiazide•Loop diuretics use for severe HPT:
▫Furosemide, Torsemide

Table 2

For potassium sparing diuretics:

1. They are usually use with diuretics that deplete potassium in the body.

2. Spironolactone is used in primary hyperaldosteronism (Conn's syndrome) & secondary hyperaldosteronism (hepatic cirrhosis complicated by ascites).

3. triamterene and amiloride are better tolerated than spironolactone.

4. main side effects of potassium sparing diuretics are hyperkalaemia. others include metabolic acidosis, skin rashes and GIT disturbances.

Osmotic diuretic:Mannitol
- use is limited
-side effects: expansion of ECF and hyponatremia

Carbonic anhydrase blockers: Acetazolamide
-used for treatment of glaucoma