Can Insulin Be Delivered via Pneumatic Tube Systems?

Jodi H. Walker, BS, PharmD

Disclosures

May 27, 2009

Question
Are insulin products stable to the shaking that occurs when sent through the pneumatic tube system?

Response from Jodi H. Walker, BS, PharmD
Adjunct Faculty, Albany College of Pharmacy, Albany, New York; Clinical Pharmacy Specialist, VA Medical Center, Bath, New York

Insulin, like other protein pharmaceuticals, has a very well-defined structure, the integrity of which must be preserved to maintain its action. Unfortunately, conformational changes can occur due to physical, chemical, and thermal stresses causing protein denaturation and aggregation, ultimately leading to impaired activity or complete inactivity.[1]

Shaking an insulin preparation can decrease the physical stability due to aggregation of the product, thereby lessening the potency. The actual protein structure can also be altered by denaturation. Mechanical stress such as vigorous shaking can cause visible clumping of the aggregates. However, the normal mechanical mixing ("rolling") of insulin suspensions to resuspend the product before administration should not cause instability.[2]

In addition, use of external insulin pumps may cause unwanted insulin conformational changes and/or aggregation due to elevated temperature from body heat as well as mechanical agitation from activities of daily living.[3]

Healthcare facilities, such as hospitals, often use pneumatic tube systems to facilitate the transportation of medications. These systems come in different shapes and sizes and use different forces for transport.[4] For these reasons, each facility is responsible for establishing its own guidelines pertaining to which medications can and cannot be sent via its pneumatic tube system, based on the system model the institution has implemented as well as the specific policies and procedures of the site.[5] Based on a review of guidelines for medication delivery via pneumatic tube system from several different hospitals, most do not send insulin or other protein-based drugs in this manner due to potential protein denaturation by mechanical stress.

A previously published statement from Eli Lilly and Company asserted that regular human insulin (Humulin®) and insulin lispro (Humalog®) products should not be delivered via the pneumatic tube system more than once and should have appropriate padding to deter breakage. No information is available on how tubing of insulin multiple times might affect the physical or chemical properties.[4]

Based on the limited information available, it may not be advantageous to risk insulin instability in the interest of quick delivery. However, the final decision to send insulin by pneumatic tube should be based on the individual facility as well as any information that your tubing system manufacturer may be able to provide.

Finally, clinicians and patients should regularly inspect insulin products and discard any products with precipitants or changes in color or clarity.

The author wishes to acknowledge Christina Kretser, PharmD student, for her contributions in researching and compiling this response.

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