Table 2: Summary of the mechanisms, advantages and disadvantages of different groups of oral antidiabetic agents.4,,6,11,23,31,36,37

Drugs   Reduction in   Mechanism of action   Advantages   Disadvantages
    HbA1C
(%)		   FPG
(mmol/L)		            
Sulphonylureas
Chlorpropamide
Tolbutamide
Glibenclamide
Glipizide
Gliclazide
Glimepiride
  0.8-2.0   3.3-3.9   increase insulin secretion and potentiate insulin action on liver and peripheral tissues.  
Rapid FPG reduction.
Low cost.
Gliclazide:
Antioxidising effect.
Glimepiride:
Manage to maintain myocardial preconditioning in comparing to glibenclamide.
 
Weight gain.
Greater risk of hypoglycaemia (lower risk for the short acting sulphonylureas).
Meglitinides:
Nateglinide
Repaglinide
  0.5-2.0   3.6-4.2   increase insulin secretion from pancreas (act on different binding sites in contrast to sulphonylureas).  
Short acting and lower risk of hypoglycaemia.
Meal adjusted dosing.
 
Frequent dosing is required.
Alpha-glucosidase inhibitors:
Acarbose
  0.7-1.0   1.9-2.2   Slow the break down and absorption of carbohydrates.  
Lower risk of hypoglycaemia.
Of advantage in patients with high PPG.
 
Gi side effects which may lead to non-compliance.
High cost.
Biguanides:
Metformin
  1.5-2.0   2.8-3.9   Decreases hepatic glucose output, increases glucose uptake and to a lesser extent, enhancing insulin sensitivity in hepatic and peripheral tissues.  
May assist in weight loss.
improvement in lipid profile.
Useful in obese patients.
Little risk of hypoglycaemia.
 

Gi symptoms: diarrhoea, nausea, vomiting, metallic taste.

Danger of lactic acidosis in renal or hepatic impaired patients.

Thiazolidinediones:
Pioglitazone
Rosiglitazone
  0.5-1.5   1.4-2.8   increase insulin sensitivity in both muscles and adipose tissue and to a lesser extent by inhibiting hepatic glucose production.  
Lower risk of hypoglycaemia.
Lower amount of insulin required.
Slight reduction of systolic and diastolic blood pressure.
improvement in lipid profile.
 
Further studies are required for the assessment in hepatotoxicity.
Suspected risk of macula oedema is associated with the use of rosiglitazone.
Weight gain, water retention (which may exacerbate congestive heart failure).
Slow onset of action.