They were first introduced in 1950s and they are still one of the most commonly used medications to decrease the high blood pressure. Diuretics have two important advantages:
- Time tested
- Least expensive and cost friendly
These are called fluid or water pills as they reduce the fluid in the body. They increase the sodium exertion in urine. This sodium takes water along with it. This means there is a smaller volume of blood pushing through our arteries, and hence less pressure on the walls.
Diuretics are the first drug of choice for persons with high blood pressure. They are more effective in persons who are more sodium sensitive, like the elderly and the blacks. Diuretics can be also used in combination with other medications. If diuretics are prescribed in the hypertensive drug regime, salt restriction is also emphasized in the diet as this reduced sodium will help the drug work more effectively.
Diuretics are classified into three groups. Each works by acting on different parts of the kidneys.
Group 1. Thiazide: most frequently used diuretics. They include:
- Bendro flumethiazide (Aprinox)
- Chlorothiazide (Cloride)
- Chlorothalidone (Hythalton)
- Hydrochlorothiazide (Esidrex)
- Indapamide (Lorvas, Indap, Natrilix)
- Methyclothiazide (Enduron)
- Metolazone (Metenix-5)
Group 2. Loop: These diuretics are stronger than thiazides. They can cause higher percentage of sodium exertion from the kidney. Loop diuretics are indicated if:
a) If thiazides are not effective
b) If there are other conditions like heart failure, kidney failure which also cause fluid retention.
Loop diuretics include:
- Bentonite (Burnet)
- Ethacrynic Acid (Edcrin)
- Furosemide (Lasix, Salinex)
Group 3. Potassium Sparing: Diuretics remove potassium also along with sodium from our blood. Potassium sparing diuretics help our body to retain potassium. These potassium sparing diuretics are used in combination with thiazides and loop diuretics.
Potassium sparing diuretics include:
- Amiloride (Amimide, Frumil)
- Spironolactone (Aldactone, Fruselac, Spiromide)
- Triamterene (Ditide, Frusemene)
The main side effect of diuretics is increased urination. The thiazide and loop diuretics cause potassium loss. To prevent this they are used in combination with a potassium-sparing diuretic.
In elderly patients, thiazide diuretics cause weakness, dizziness on standing. These drugs can cause impotence in some men but this is a very rare phenomenon. Once these drugs are stopped, the side effects disappear but this should be done only under a doctor’s supervision. High doses of thiazide diuretics can increase the blood sugar level and total blood cholesterol levels. In some rare cases an increase in uric acid levels can lead to gout, a joint disorder in which abnormal uric acid crystals get deposited on the joints.
Loop diuretics can sometimes lead to dehydration. Potassiumsparing diuretics can increase the body potassium levels too much leading to ‘hyperkalemia’. If there is a kidney disease, potassium sparing diuretics are to be avoided because it can lead to arrhythmia (abnormal heart rhythms) which is an effect of high potassium concentration in blood.