Kalten combines three medicines that have different ways of working (modes of action) and leads to greater lowering of blood pressure in more people than with each medicine used alone.

• Atenolol belongs to the group of medicines called beta-blockers.
  
  
  • It works by blocking the action of two chemicals, called adrenaline (a hormone signal carried in the blood) and noradrenaline (released from nerves supplying the heart), which control the heart rate and force of beating.
    
    
  • It does this by stopping adrenaline and noradrenaline from attaching themselves (binding) to special sites, called beta-receptors, in the heart, so they can’t produce their effects.
    
    
  • Atenolol reduces the heart rate and the force of heart muscle contraction and lowers blood pressure, partly by altering the action of the nervous system on the heart.
    
    
• Hydrochlorothiazide is a diuretic (water pill).
  
  
  • It works by stopping the re-absorption of salt and water from the kidneys back into the bloodstream.
    
    
  • This results in increased urine output (diuresis) and an increased sodium loss in the urine. These effects lower the blood pressure.
    
    
• Amiloride is also a diuretic, but it works in a different way.
  
  
  • It blocks salt re-absorption from the kidneys, but also stops potassium from being lost.
    
    
  • Potassium is vital for the normal operation of the nervous system, muscles and the kidneys.