How should I write the prescription for continuous subcutaneous insulin pump infusion of insulin lispro (Humalog) 100 U/mL with a total daily dose ≤ 100 U?

How to Write a Prescription for Continuous Subcutaneous Insulin Infusion with Insulin Lispro

Write the prescription as: "Insulin lispro (Humalog) 100 units/mL for continuous subcutaneous insulin infusion via insulin pump. Dispense [quantity based on total daily dose × 30-90 days]. Administer via insulin pump per patient's programmed basal and bolus settings, total daily dose not to exceed 100 units." 1, 2

Essential Prescription Components

Insulin Specification

• Specify insulin lispro 100 units/mL (U-100) concentration only — the U-200 formulation is contraindicated for pump use and must never be prescribed for continuous subcutaneous insulin infusion 2
• State "for continuous subcutaneous insulin infusion (CSII)" or "for insulin pump use" explicitly on the prescription 1, 2
• Use the brand name (Humalog or Lyumjev) or specify "insulin lispro" to avoid confusion with other insulin types 2

Quantity Calculation

• Calculate the dispensed quantity based on the patient's total daily insulin dose multiplied by the coverage period (typically 30-90 days) 1
• For a patient using up to 100 units daily, prescribe 3,000 units (one 10-mL vial) for 30 days, or 9,000-10,000 units (three to four 10-mL vials or equivalent in cartridges/pens) for 90 days 1, 2
• Most pump reservoirs hold 200-300 units, providing 4-6 days of insulin for patients using 50 units daily; adjust quantities accordingly 3

Delivery Instructions

• Specify "administer via insulin pump per programmed basal and bolus settings" rather than listing specific doses, as pump therapy involves individualized programming 1, 2
• Note that approximately 50% of total daily insulin is delivered as continuous basal infusion and 50% as meal boluses 3
• The pump itself provides basal coverage through continuous delivery of rapid-acting insulin — no separate long-acting insulin is used 3

Critical Safety Elements to Include

Mandatory Backup Prescription

• Always prescribe backup rapid-acting insulin in vials or pens — pump failure can lead to ketoacidosis within hours since no long-acting insulin is on board 3
• Include on the prescription: "Patient must carry backup insulin lispro vials/pens for emergency use in case of pump malfunction" 3

Glucagon Co-Prescription

• The American Diabetes Association mandates that all patients on insulin pump therapy receive a prescription for glucagon to treat severe hypoglycemia 1
• Write a separate prescription for glucagon emergency kit 1

Dosing Warnings

• Include the warning: "Do NOT transfer insulin from pen to syringe" if prescribing pen cartridges, as this can cause severe overdosage 2
• Specify "For subcutaneous use only via insulin pump" to prevent inadvertent intravenous administration 2

Infusion Set Management Instructions

Rotation and Changing Schedule

• Instruct patients to rotate infusion sites within the same region (abdomen, upper arm, thigh, or buttocks) to reduce risk of lipodystrophy and localized cutaneous amyloidosis 2
• Soft infusion sets should be changed every 2-5 days (mean 4.8 days), while metal needle sets require more frequent changes every 1.5-4 days (mean 3.8 days) 4
• Patients experiencing frequent catheter occlusions should use shorter intervals between infusion set changes 4

Sample Prescription Format

Rx: Insulin lispro (Humalog) 100 units/mL
Sig: For continuous subcutaneous insulin infusion via insulin pump. Administer per programmed basal and bolus settings. Total daily dose not to exceed 100 units. Rotate infusion sites. Change infusion set every 2-4 days.
Disp: 10 mL vial (1000 units/vial) × 3 vials (30-day supply)
Refills: 11 (for 1-year coverage)
Additional: Patient must carry backup insulin lispro pen/vial for pump failure. Prescribe glucagon emergency kit separately.

1, 2

Common Pitfalls to Avoid

• Never prescribe U-200 insulin lispro for pump use — only U-100 formulation is approved for CSII 2
• Never prescribe long-acting insulins (glargine, detemir, degludec) for pump use — these are designed for injection, not continuous infusion 3, 5
• Never mix insulins in pump reservoirs — only pure rapid-acting insulin analog formulations should be used 1
• Do not prescribe regular human insulin for pumps when rapid-acting analogs are available, as lispro provides superior postprandial glucose control and improved HbA1c reduction (−0.62% vs −0.09%, P=0.01) 6