Insulin and hypoglycaemic agents are essential for the management of diabetes mellitus, a condition characterised by high blood glucose levels. These medications help control blood sugar levels, either by increasing insulin production, enhancing insulin sensitivity, or reducing glucose production.
Insulin
Mechanism of Action: Insulin is a hormone produced by the beta cells in the pancreas. It facilitates the uptake of glucose into cells, particularly muscle and fat cells, and inhibits glucose production in the liver.
Types of Insulin:
- Rapid-Acting Insulin:
- Medications: Insulin lispro (Humalog), insulin aspart (NovoRapid), insulin glulisine (Apidra).
- Onset: 10-20 minutes.
- Peak: 1-3 hours.
- Duration: 3-5 hours.
- Uses: Taken before meals to control postprandial blood glucose spikes.
- Short-Acting Insulin:
- Medications: Regular insulin (Actrapid).
- Onset: 30 minutes.
- Peak: 2-3 hours.
- Duration: 8 hours.
- Uses: Taken 30 minutes before meals.
- Intermediate-Acting Insulin:
- Medications: Isophane insulin (Humulin I, Insulatard).
- Onset: 1-2 hours.
- Peak: 4-12 hours.
- Duration: 12-18 hours.
- Uses: Provides basal insulin coverage.
- Long-Acting Insulin:
- Medications: Insulin glargine (Lantus), insulin detemir (Levemir), insulin degludec (Tresiba).
- Onset: 1-2 hours.
- Peak: No significant peak.
- Duration: Up to 24 hours.
- Uses: Provides consistent basal insulin levels.
- Pre-Mixed Insulin:
- Medications: NovoMix 30, Humalog Mix 25.
- Uses: Combines rapid-acting and intermediate-acting insulins to cover both basal and postprandial glucose control.
Side Effects:
- Hypoglycaemia
- Weight gain
- Injection site reactions
Considerations:
- Dose adjustments may be necessary based on blood glucose monitoring.
- Storage conditions vary; some insulins need refrigeration.
Oral Hypoglycaemic Agents
- Biguanides:
- Medication: Metformin.
- Mechanism of Action: Reduces hepatic glucose production and increases insulin sensitivity in peripheral tissues.
- Uses: First-line therapy for type 2 diabetes.
- Side Effects: Gastrointestinal upset, lactic acidosis (rare).
- Considerations: Should be taken with meals to reduce gastrointestinal side effects.
- Sulfonylureas:
- Medications: Gliclazide, glibenclamide.
- Mechanism of Action: Stimulate insulin secretion from pancreatic beta cells.
- Uses: Type 2 diabetes, usually as a second-line therapy.
- Side Effects: Hypoglycaemia, weight gain.
- Considerations: Risk of hypoglycaemia, particularly in elderly patients or those with renal impairment.
- Thiazolidinediones (TZDs):
- Medications: Pioglitazone.
- Mechanism of Action: Increase insulin sensitivity in muscle and adipose tissue.
- Uses: Type 2 diabetes.
- Side Effects: Weight gain, oedema, risk of heart failure.
- Considerations: Contraindicated in patients with heart failure or history of bladder cancer.
- DPP-4 Inhibitors:
- Medications: Sitagliptin, saxagliptin.
- Mechanism of Action: Inhibit the enzyme DPP-4, increasing levels of incretin hormones which increase insulin release and decrease glucagon levels.
- Uses: Type 2 diabetes.
- Side Effects: Nasopharyngitis, pancreatitis (rare).
- Considerations: Generally well-tolerated, minimal risk of hypoglycaemia.
- SGLT2 Inhibitors:
- Medications: Canagliflozin, dapagliflozin.
- Mechanism of Action: Inhibit SGLT2 in the kidneys, reducing glucose reabsorption and increasing glucose excretion in urine.
- Uses: Type 2 diabetes.
- Side Effects: Urinary tract infections, genital infections, dehydration.
- Considerations: Benefits in reducing cardiovascular events and slowing progression of kidney disease.
- GLP-1 Receptor Agonists:
- Medications: Exenatide, liraglutide.
- Mechanism of Action: Mimic the incretin hormone GLP-1, increasing insulin secretion, decreasing glucagon release, and slowing gastric emptying.
- Uses: Type 2 diabetes.
- Side Effects: Nausea, risk of pancreatitis.
- Considerations: May assist with weight loss, useful in patients with cardiovascular disease.