Glyzeric Mechanism of Action

Pharmacology: Pharmacodynamics: Gliclazide: Gliclazide is a hypoglycaemic sulfonylurea antidiabetic active substance differing from other related compounds by an N-containing heterocyclic ring with an endocyclic bond.
Gliclazide reduces blood glucose levels by stimulating insulin secretion from the β-cells of the islets of Langerhans. Increase in postprandial insulin and C-peptide secretion persists after two years of treatment.
In addition to these metabolic properties, gliclazide has haemovascular properties.
Metformin: Metformin is a biguanide with antihyperglycaemic effects, lowering both basal and postprandial plasma glucose. It does not stimulate insulin secretion and therefore does not produce hypoglycaemia.
Metformin may act via 3 mechanisms: Reduction of hepatic glucose production by inhibiting gluconeogenesis and glycogenolysis.
In muscle, by increasing insulin sensitivity, improving peripheral glucose uptake and utilization.
And delay of intestinal glucose absorption.
Metformin stimulates intracellular glycogen synthesis by acting on glycogen synthase.
Metformin increases the transport capacity of all types of membrane glucose transporters (GLUTs) known to date.
Pharmacokinetics: Gliclazide: Absorption: Plasma levels increase reaching maximal concentrations between 2 and 6 hours. Gliclazide is well absorbed. Food intake does not affect the rate or degree of absorption.
Distribution: Plasma protein binding is approximately 95%. The volume of distribution is around 19 litres.
Biotransformation: Gliclazide is mainly metabolised in the liver and excreted in the urine; less than 1% of the dose is excreted unchanged in the urine. No active metabolites have been detected in plasma.
Elimination: The elimination half-life of gliclazide is between 10 and 12 hours.
Metformin: Absorption: After an oral dose of metformin hydrochloride tablet, maximum plasma concentration (Cmax) is reached in approximately 2.5 hours (tmax). Absolute bioavailability of a 500 mg or 850 mg metformin hydrochloride tablet is approximately 50-60% in healthy subjects. After an oral dose, the non-absorbed fraction recovered in faeces was 20-30%. After oral administration, metformin absorption is saturable and incomplete. It is assumed that the pharmacokinetics of metformin absorption is non-linear.
At the recommended metformin doses and dosing schedules, steady state plasma concentrations are reached within 24 to 48 hours and are generally less than 1 microgram/ml. In controlled clinical trials, maximum metformin plasma levels (Cmax) did not exceed 5 microgram/ml, even at maximum doses.
Food decreases the extent and slightly delays the absorption of metformin. Following oral administration of 850 mg tablet, a 40% lower plasma peak concentration, a 25% decrease in AUC (area under the curve) and a 35 minute prolongation of the time to peak plasma concentration were observed. The clinical relevance of these findings is unknown.
Distribution: Plasma protein binding is negligible. Metformin partitions into erythrocytes. The blood peak is lower than the plasma peak and appears at approximately the same lime. The red blood cells most likely represent a secondary compartment of distribution. The mean volume of distribution (Vd) ranged between 63-276 L.
Metabolism: Metformin is excreted unchanged in the urine. No metabolites have been identified in humans.
Elimination: Renal clearance of metformin is > 400 ml/min, indicating that metformin is eliminated by glomerular filtration and tubular secretion. Following an oral dose, the apparent terminal elimination half-life is approximately 6.5 hours.
When renal function is impaired, renal clearance is decreased in proportion to that of creatinine and thus the elimination half-life is prolonged, leading to increased levels of metformin in plasma.