Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1   Pharmacodynamic properties

Pharmacotherapeutic group:
Solutions for parenteral nutrition, carbohydrates, ATC code: B05B A03 
Pharmacodynamic effects:
Glucose is metabolised ubiquitously as the natural substrate of the cells of the body.
Under physiological conditions glucose is the most important energy-supplying carbohydrate with a caloric value of approx. 16.7 kJ/g or 4 kcal/g. In adults, the normal concentration of glucose in blood is reported to be 70 – 100 mg/dl or 3.9 to 5.6 mmol/l (fasting).

Pharmacokinetic Properties

5.2   Pharmacokinetic properties
Absorption
Since the solution is administered intravenously, its bioavailability is 100%.

Distribution
After infusion, glucose is first distributed in the intravascular space and then is taken up into the intracellular space.

Biotransformation
In glycolysis, glucose is metabolised to pyruvate or to lactate. Under aerobic conditions pyruvate is completely oxidized to carbon dioxide and water. In case of hypoxia, pyruvate is converted to lactate. Lactate can be partially re-introduced into the glucose metabolism (Cori cycle).
Glucose utilisation disturbances (glucose intolerance) can occur under conditions of pathological metabolism. These mainly include diabetes mellitus and states of metabolic stress (e.g. intra-, and postoperatively, severe disease, injury), hormonally mediated depression of glucose tolerance, which can even lead to hyperglycaemia without exogenous supply of the substrate. Hyperglycaemia can – depending on its severity – lead to osmotically mediated renal fluid losses with consecutive hypertonic dehydration, to hyperosmotic disorders up to and including hyperosmotic coma.
Metabolism of glucose and electrolytes are closely related to each other. Insulin facilitates potassium influx into cells. Phosphate and magnesium are involved in the enzymatic reactions associated with glucose utilization. Potassium, phosphate and magnesium requirements may therefore increase following glucose administration and may therefore have to be monitored and supplemented according to individual needs. Especially cardiac and neurological functions may be impaired without supplementation.

Elimination
The final products of the complete oxidation of glucose are eliminated via the lungs (carbon dioxide) and the kidneys (water).
Practically no glucose is excreted renally by healthy persons. In pathological metabolic conditions (e.g. diabetes mellitus, postaggression metabolism) associated with hyperglycaemia, glucose is also excreted via the kidneys (glucosuria) when the maximum tubular resorption capacity is exceeded (at blood glucose levels higher than 160-180 mg/dl or 8.8-9.9 mmol/l).