Differential flow rate of commercially available triamcinolone with and without preservative through small-gauge needles.

Objective: To compare the flow rate through different gauge needles of triamcinolone acetonide with benzyl alcohol (TABA) versus preservative-free triamcinolone acetonide injectable suspension (TAIS).

Materials And Methods: Experimental injections of 1 mL of TABA or TAIS were performed through a 27-, 30-, or 32-gauge needle. A piezoelectric pressure transducer connected to a personal computer was placed between the syringe and needle to record the force-time relationship and assess the flow rate (mL/s). Measurements were performed in triplicate.

Results: Flow rates were similar between preparations using a 27-gauge needle. Using a 30-gauge needle, the flow rate was 0.058 mL/s for TABA and 0.178 mL/s for TAIS. Using a 32-gauge needle, no flow was sustained by TABA, whereas the flow rate of TAIS was 0.114 mL/s (P < .05).

Conclusion: TAIS can be injected through a 32-gauge needle without the risk of obstruction. Occlusions were seen with TABA using the 30- and 32-gauge needles.