Diuretic

Diuretics were the first medicines to be prescribed to treat arterial hypertension (AHT). They all have the common feature of removing sodium in urine. Apart from HT they are also indicated for oedema, heart failure and renal failure.

How do diuretics work ?

The main classes of diuretics are the thiazides, the loop diuretics and the potassium sparing diuretics. The first two categories of diuretics remove both sodium and potassium and cause vasodilatation. The last type help remove sodium but at the same time spare potassium. When prescribed at low doses, all of these medicines lose their diuretic effect but keep their vasodilating effects.

Contraindications or precautions?

Thiazide diuretics and loop diuretics cause hyponatraemia, (i.e. an abnormal fall in sodium concentration in the blood) and hypokalaemia due to an abnormal fall in potassium concentrations. However, potassium diuretics also cause a fall in magnesium (magnesaemia) as well as hyperkalaemia . Association of some diuretics with some medicines such as the anti-inflammatory drugs is contraindicated. It should also be noted that loop diuretics can trigger or worsen type 2 diabetes in a patient with the metabolic syndrome.

Sources:

• Manuel Merck – 4^e French edition hypertension
• committee – Pharmacorama, 9 June 2011