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Keys to Exploring Syringeability Cheat Sheet by

medical     syringeability

1. Fulfill prereq­uisites

Select a suitable placebo fluid to emulate 'real' drug-p­roduct rheology safely and at acceptable cost, which is not always easy. (Note that results must be confirmed with the actual drug product once choices are narrowed).
Design and procure suitable fixtures to locate syringe and operate plunge­r/p­lunger stopper in test equipment.
Conduct a risk analysis to identify potential risks and failure modes associated with the delivery of the placebo fluid with a syringe, as:
        Placebo toxicity hazard (e.g., irritant proper­ties)
        Possible needle­-stick injury in later handling trials.
Some initial testing is useful to establish ballpark values; therea­fter, modest sample sizes (as small as 10) may be sufficient to allow meaningful analysis.

2. Select materials

Identify a range of syringe body sizes (volume and bore), in glass (and/or COP if required). suitable to deliver the required volume­/dose.
Identify a range of stoppers to suit the chosen syringes (these may include low-fr­iction' coated variants).
Identify a range of needle gauges and lengths suited to the desired delivery (i.e.. subcut­aneous, intram­usc­ular, intrad­ermal, etc.).

3. Conduc­tst­ruc­tured series of lab experi­ments

Conduct a structured series of laboratory experi­ments to:
Establish injection force profiles (incl. break-­loose and maximum extrusion force). for pre-se­lected injection times
        Use of a tensile load test machine able to capture, display and store force, displa­cement and time data is recomm­ended.
Investigate how typical delivery profiles are affected by parameters such as:
        Fluid temper­ature
        Injection (test machine crosshead) speed.
Explore limits of the mechanical integrity of the injection system, such as:
        Peak forces acting on syringe flanges, as these can cause flange failure
        Crippling/buckling failure of slender plunger rods at start of delivery stroke.
Refine initial risk analysis with laboratory findings and select candidate device presen­tat­ions.
Perform 'empty syringe' testing to determine break-­loose and glide forces.
Sample sizes should be sufficient to support statis­tical analysis of outputted data (e.g n> or equal to 30).
 

Syringe Parts

4. Compare empirical results

Compare empirical results with mathem­ati­cally predicted results
Don't expect the empirical results to perfectly match the predicted values.
Use the two to deepen unders­tan­din­g—why do they differ?
Take the opport­unity to refine the math model and/or test procedure and re-test.
Complete alignment of practical with theore­tical answers is not essential. A better unders­tanding of syringe perfor­mance is the real objective.

5. Validate options with carefully

Validate options with carefully chosen users via simulated use studies
Initially by an experi­enced human factor engineer
Then with a healthcare profes­sional experi­enced in the injection of viscous drugs

Conclusion

Always bear in mind that laboratory perfor­mance measured using a tensile test machine can only provide some guidance to perfor­mance in a user's hand, not mimic it. However, laboratory testing and mathem­atical modeling inform choices. highlight options. and provide a framework of unders­tanding that is invalu­able.

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