InterTech Design Report (DR-175)

Updating Functional Tests for Accurate Dosing of Higher Viscosity Drugs

The Challenge:

Functionally testing medical devices or performing sufficient audit testing to assure quality of drug delivery or blood collection devices are not new requirements. What is new, however, is the need to measure much smaller volumes – as small as one microliter. Medical device manufactures seek to use deterministic test methods to assure the reliability of new generation devices used both in clinical settings and in home self-care environments. 

These inherent challenges are amplified by recent advances in therapeutic proteins and more targeted drug products that encumber drawing and weighing methods with handling higher viscosity liquids. With these newer drugs, conventional delivery is precluded due to the need for longer injection times to reduce patient discomfort. Instead, smart injectors, infusion pumps and/or digital pills are the drug delivery devices of choice for a wide range of these high viscosity protein-based therapeutics. These devices enable low volume dispensing over a longer period of time. 

Historically, makers of collection tubes and drug delivery systems have relied on drawing and weighing methods to test the accuracy of their devices. Weighing must be done twice – before and after – introducing significant measurement uncertainties at both stages, as well as an increase in potential effects of ambient temperature variations affecting laminar flow and introducing distortions from vibrations. 

Traditional drawing and weighing methods are not up to the challenge – whether one is testing in-line or with extensive audit testing – to ensure that the specified drug volumes are delivered accurately. A key objective today is to cultivate a risk-based approach in the product development phase that allows medical device manufacturers to leverage testing as a means to better analyze and ultimately eliminate risks of releasing defective products to clinical and homecare settings.

InterTech Solution & Technology

InterTech’s test method correlates fluids with dry air testing, eliminating the need for cumbersome conventional flowmeters. InterTech MicroScale MED75 testers can detects leaks of 0.008 sccm with a test time of 10 seconds or less and GR&R of less than 20%.
This InterTech technique using the air pressure rise to measure liquid flow significantly improves accuracy and repeatability by eliminating the variable effects of bulk modulus (fluid compressibility) and temperature that distort results in conventional test methods.