Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1   Pharmacodynamic properties
Pharmacotherapeutic group
Solutions affecting the electrolyte balance
ATC code: B05B B01
Potassium is the major cation of intracellular fluid and is essential for maintenance of acid- base balance, isotonicity, and electrodynamic characteristics of the cell. The electrolyte is an important activator in many enzymatic reactions and is essential to a number of physiologic processes including transmission of nerve impulses, contraction of cardiac, smooth, and skeletal muscles, gastric secretion, renal function, tissue synthesis, carbohydrate utilisation and protein synthesis.
Sodium is the major cation of the extracellular fluid and is principally responsible for the control of water distribution, fluid and electrolyte balance, and osmotic pressure of body fluids. Together with chloride and bicarbonate, sodium plays also an important role in the regulation of acid-base balance.
Chloride, the major extracellular anion, closely follows the physiologic disposition of sodium and changes in the acid-base balance of the body are reflected by changes in serum chloride concentration.
Pharmacodynamic effects
In postoperative, posttraumatic and other clinical instances severe fluid and electrolyte losses are frequently observed and the above named physiologic functions are impaired. In these patients the application of the components contained in Potassium Chloride 0.3% w/v and Sodium Chloride 0.9% w/v is indicated to restore fluid and electrolyte levels and thus prevent further damage to the body.

Pharmacokinetic Properties

5.2   Pharmacokinetic properties
Absorption
Since the ingredients of Potassium Chloride 0.3% w/v and Sodium Chloride 0.9% w/v are infused intravenously their bioavailability is 100 %.Distribution
Infused potassium is actively transported into the cells, where its concentration is up to 40 times that outside the cell. Plasma potassium concentrations generally range from 3.5- 5 mmol/l. Sodium and chloride mainly distribute in the extracellular space. Plasma sodium concentration is normally regulated at a concentration of 135-145 mmol/l and chloride at 95- 107 mmol/l.
Biotransformation
Although sodium, potassium and chloride is absorbed, distributed and excreted, there is no metabolism in the strict sense.
The kidneys are the major regulator of the sodium and water balances. In co-operation with the hormonal control mechanisms (renin-angiotensin-aldosterone system, antidiuretic hormone) and the hypothetical natriuretic hormone they are primarily responsible for keeping the volume of the extracellular space constant and regulating its fluid composition.
Factors influencing potassium transfer between intracellular and extracellular fluid such as acid-base disturbances can distort the relationship between plasma concentrations and total body stores Chloride is exchanged for hydrogen carbonate in the tubule system and is, thus, involved in the regulation of the acid base balance.
Elimination
The kidneys are the main route of excretion for potassium, sodium, and chloride but small amounts are lost via the skin and intestinal tract. Especially surgery results in increased urinary excretion of potassium while water and sodium is retained. For supplementation it is essential to take into consideration that the homeostasis of the single electrolytes is influenced by the others and their regulation is thus interdependent to some degree.