💊 Insulin
Drug Class & Overview
Insulin is a hormone replacement therapy, a polypeptide hormone produced by the beta cells of the pancreatic islets, crucial for glucose homeostasis. It is the primary treatment for Type 1 Diabetes Mellitus and is used in Type 2 Diabetes Mellitus when oral agents are insufficient.
Mechanism of Action
Insulin binds to specific receptors on target cells (e.g., liver, muscle, adipose tissue), promoting glucose uptake and utilisation. It stimulates glycogenesis in the liver and muscle, inhibits gluconeogenesis and glycogenolysis, and promotes lipogenesis while inhibiting lipolysis.
Key Indications
Insulin is indicated for all patients with Type 1 Diabetes Mellitus. In Type 2 Diabetes Mellitus, it is used when glycaemic control is not achieved with oral agents, during periods of acute illness, or in pregnancy. It is also used in hyperkalaemia to shift potassium intracellularly.
Contraindications
There are no absolute contraindications to insulin therapy when indicated for life-sustaining treatment, such as in Type 1 Diabetes. However, caution is required in patients prone to hypoglycaemia, and dose adjustments are essential in renal or hepatic impairment due to altered metabolism and clearance.
Adverse Effects
The most common and serious adverse effect is hypoglycaemia, which can be life-threatening. Other common side effects include weight gain, lipodystrophy at injection sites (hypertrophy or atrophy), and local allergic reactions such as redness or itching.
Monitoring
Regular monitoring of blood glucose levels is essential, often multiple times daily, to guide dose adjustments. HbA1c is monitored every 3-6 months to assess long-term glycaemic control. Renal function should be monitored periodically, especially in patients with comorbidities.
Prescribing Safety (OSCE)
When prescribing insulin, always check for known allergies, though true insulin allergy is rare. Be aware of drug interactions that can affect glucose levels, such as corticosteroids (increase) or beta-blockers (mask hypoglycaemia). Counsel patients thoroughly on injection technique, site rotation, storage, and recognition/management of hypoglycaemia.
MLA High-Yield Notes
Insulin is life-saving in Type 1 Diabetes. Understand the different insulin preparations (e.g., Novorapid, Humalog, Levemir, Lantus) and their onset/duration of action. Hypoglycaemia is the most critical adverse effect to recognise and manage. Emphasise patient education on self-management.
Common SBA Themes
SBAs often focus on identifying and managing hypoglycaemia, differentiating between types of insulin (e.g., rapid-acting vs. long-acting), and understanding the indications for insulin in Type 2 Diabetes. Questions may also test knowledge of insulin storage and administration techniques.
References
- BNF (British National Formulary)
- NICE Guideline NG28: Type 1 diabetes in adults: diagnosis and management
- NICE Guideline NG28: Type 2 diabetes in adults: management