1. Chapter Overview
This chapter establishes the standard of care for Type 1 Diabetes (T1D): Basal-Bolus injection therapy (MDI) or Continuous Subcutaneous Insulin Infusion (CSII/Pump).
For the CDE exam, the focus is rarely on “how to inject,” but rather on insulin pharmacokinetics (why we choose analogues over human insulin) and the indications for advanced therapies (when to switch from MDI to Pump or Sensor-Augmented Pump). You must also understand the emerging, though cautious, data on non-insulin adjunctive therapies.
2. Key Messages (The "Gold Nuggets")
The Standard: Basal-bolus (MDI) or CSII are the only preferred regimens. Premixed insulins are generally not suitable for adults with T1D.
Safety First: The primary driver for choosing long-acting basal analogues (e.g., glargine, detemir, degludec) over NPH is the reduction of hypoglycemia, specifically nocturnal hypoglycemia.
Rapid is Better: Rapid-acting insulin analogues (RAIA) are preferred over short-acting (regular) insulin because they improve postprandial glucose and lower A1C without increasing hypoglycemia.
The Pump Candidate: CSII is not just for people with high A1C. It is specifically indicated for those with severe hypoglycemia, hypoglycemia unawareness, or a significant “Dawn Phenomenon.”
3. Insulin Pharmacotherapy
A. Basal Insulins
Goal: Control glucose in the fasting state and between meals.
Long-Acting Analogues (Detemir, Glargine U-100): Lower fasting glucose and less nocturnal hypoglycemia compared to NPH.
Ultra-Long Acting (Glargine U-300, Degludec):
Glargine U-300 (Toujeo): Longer duration (>30 hours) and flatter profile than U-100.
Degludec (Tresiba): Duration of ~42 hours. Associated with less nocturnal hypoglycemia and lower total insulin dose compared to glargine or detemir. Allows for flexible dosing timing.
B. Bolus Insulins
Goal: Control glycemic rise at meals.
Rapid-Acting Analogues (Aspart, Lispro, Glulisine): Administer 0–15 minutes before meals.
Faster-Acting Aspart (Fiasp): Can be administered at the start of the meal or up to 20 minutes after starting. Demonstrated superior postprandial control vs. insulin aspart.
4. Advanced Technologies: CSII and SAP
A. Continuous Subcutaneous Insulin Infusion (CSII / Pump)
Indications: Consider CSII if MDI is optimized but targets are not met, OR if the patient has:
Significant glucose variability.
Frequent severe hypoglycemia or hypoglycemia unawareness.
Significant “Dawn Phenomenon” (rise in BG early morning).
Very low insulin requirements (requiring micro-dosing).
Women contemplating pregnancy.
Outcomes: Lowers A1C by ~0.3% compared to MDI; improves Quality of Life (QOL) and Treatment Satisfaction.
B. Sensor-Augmented Pump (SAP)
Definition: Insulin pump combined with Continuous Glucose Monitoring (CGM).
Benefit: A1C reduction is superior to MDI or Pump alone.
Low Glucose Suspend: Pumps equipped with this feature (stopping insulin when low) significantly reduce nocturnal hypoglycemia without raising A1C or causing ketoacidosis.
5. Adjunctive Therapies (Non-Insulin)
The guidelines reviewed using Type 2 medications in Type 1 diabetes. Note: These are generally off-label uses.
Metformin: May reduce insulin requirements and lead to modest weight loss, but does NOT result in sustainable A1C improvement.
GLP-1 Receptor Agonists (e.g., Liraglutide): Associated with weight loss and insulin dose reduction, but inconsistent A1C results.
SGLT2 Inhibitors:
Showed reduction in A1C and weight.
Major Warning: Significant risk of Diabetic Ketoacidosis (DKA), including “euglycemic DKA” (DKA with normal blood sugars). Currently, they do not have an indication for T1D in Canada.
6. Diabetes Canada Clinical Practice Guidelines Recommendations
Key Recommendations to Memorize:
Regimen: Basal-bolus injection or CSII should be used to achieve glycemic targets. (Grade A, Level 1A).
Basal Choice: A long-acting insulin analogue (Detemir, Glargine, Degludec) may be used in place of NPH to reduce the risk of nocturnal hypoglycemia. (Grade B, Level 2).
Degludec Specifics: Degludec may be used instead of detemir or glargine U-100 to reduce nocturnal hypoglycemia. (Grade B/C).
Bolus Choice: Rapid-acting analogues should be used over regular insulin to improve A1C and minimize hypoglycemia. (Grade B, Level 2).
Hypoglycemia Unawareness: Strategies to restore awareness include:
Standardized education (Grade A, Level 1A).
Relaxed glycemic targets for up to 3 months (Grade C, Level 3).
Sensor-Augmented Pump with Low Glucose Suspend (Grade B, Level 2).
Technology: In adults not achieving targets (on MDI or CSII), CGM should be considered to improve A1C. (Grade B, Level 2).