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Accuracy and reproducibility of low dose insulin administration using pen-injectors and syringes
M G Gnanalingham1, P Newland, C P Smith
1Department of Paediatrics, Booth Hall Children's Hospital, Blackley, Manchester, UK.
Insights
Insulin pens and syringes show significant inaccuracies with small doses, especially 1 U. Device changes can alter insulin delivery, requiring patient education on dose variability.
Area of Science:
- Pediatrics
- Endocrinology
- Pharmaceutical Technology
Background:
- Many children with diabetes require small insulin doses, often 1-2 U.
- Syringes and pen-injectors are commonly used for insulin delivery in pediatric patients.
- Accurate and reproducible delivery of small insulin doses is critical for glycemic control.
Purpose of the Study:
- To evaluate the accuracy and reproducibility of small insulin doses (1, 2, 5, and 10 U) delivered by NovoPens, BD-Pens, and syringes.
- To compare the performance of pen-injectors versus traditional syringes for low-dose insulin administration.
- To identify potential inaccuracies in insulin delivery devices used in pediatric diabetes care.
Main Methods:
- 1, 2, 5, and 10 U doses of soluble insulin were dispensed 15 times each from NovoPens, BD-Pens, and 30 U syringes.
- Doses were randomly ordered and dispensed by nurses.
- Each dispensed dose was weighed to compare intended versus actual insulin delivery.
Main Results:
- Pen-injectors delivered less insulin than syringes, with differences inversely proportional to dose.
- For 1 U doses, mean errors were 11(4)% for NovoPen, 8(3)% for BD-Pen, and 23(9)% for syringes.
- Accuracy of pen-injectors was similar and superior to syringes for 1, 2, and 5 U doses, though reproducibility was similar across all devices (<7% CV).
Conclusions:
- All tested devices, particularly syringes, demonstrate unacceptable inaccuracy for 1 U insulin doses.
- Pen-injectors consistently underdosed, while syringes tended to overdose at low volumes.
- Patients on low insulin doses must be educated about potential dose alterations when switching between devices.
Abstract:
Many children with diabetes require small doses of insulin administered with syringes or pen-injector devices (at the Booth Hall Paediatric Diabetic Clinic, 20% of children aged 0-5 years receive 1-2 U insulin doses). To determine how accurately and reproducibly small doses are delivered, 1, 2, 5, and 10 U doses of soluble insulin (100 U/ml) were dispensed in random order 15 times from five new NovoPens (1.5 ml), five BD-Pens (1.5 ml), and by five nurses using 30 U syringes. Each dose was weighed, and intended and actual doses compared. The two pen-injectors delivered less insulin than syringes, differences being inversely proportional to dose. For 1 U (mean (SD)): 0.89 (0.04) U (NovoPen), 0.92 (0.03) U (BD-Pen), 1.23 (0.09) U (syringe); and for 10 U: 9.8 (0.1) U (NovoPen), 9.9 (0.1) U (BD-Pen), 10.1 (0.1) U (syringe). The accuracy (percentage errors) of the pen-injectors was similar and more accurate than syringes delivering 1, 2, and 5 U of insulin. Errors for 1 U: 11(4)% (NovoPen), 8(3)% (BD-Pen), 23(9)% (syringe). The reproducibility (coefficient of variation) of actual doses was similar (< 7%) for all three devices, which were equally consistent at underdosing (pen-injectors) or overdosing (syringes) insulin. All three devices, especially syringes, are unacceptably inaccurate when delivering 1 U doses of insulin. Patients on low doses need to be educated that their dose may alter when they transfer from one device to another.