Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1.   Pharmacodynamic properties
Pharmacotherapeutic group
IV solutions, solutions affecting the electrolyte balance, electrolytes ATC code: B05B B01

Mechanism of action
The pharmacological properties of sodium bicarbonate result from its physiological role in the HCO3-/CO2 buffer system.

Pharmacodynamic effects
Exogenously administered sodium bicarbonate rapidly absorbs hydrogen ions from the extracellular space and thus leads to a rise of the pH in the organism.

Secondary pharmacodynamic effects

Alterations in plasma bicarbonate levels can result in changes in the plasma potassium concentration. An increase in bicarbonate concentration causes a shift of potassium into the cells, whereas a decrease has the opposite effect. This effect may aggravate existing hyperkalaemia or cause hypokalaemia.
An increase in pH due to increasing bicarbonate concentration, will also cause a decrease in the ionised calcium concentration. This is due to the increased binding of calcium to plasma proteins, especially albumin. This reduction of plasma calcium levels could contribute to the myocardial depressive effects of bicarbonate administration.

Pharmacokinetic Properties

5.2.   Pharmacokinetic properties

Distribution
Bicarbonate readily passes across the placental barrier but it passes only slowly across the blood-brain barrier.

Elimination

In the kidneys, bicarbonate is filtered in the glomeruli and the major proportion of it is re- absorbed in the tubules. When plasma bicarbonate concentrations rise to above 24 mmol/l, bicarbonate is excreted by the kidneys. Renal bicarbonate re-absorption is reduced under therapy with diuretics of the thiazide group or those acting on the loop of HENLE.