Measurement of the actual dose of triamcinolone acetonide delivered by common techniques of intravitreal injection.
OBJECTIVE
To measure the actual dose of triamcinolone acetonide (TA) delivered during intravitreal injection performed by several common techniques.


METHODS
Experimental study.


METHODS
A 0.1-ml, 40-mg vial of TA (Kenalog-40; Bristol-Myers-Squibb, Peapack, New Jersey, USA) was prepared according to one of four protocols and the mass determined after drying overnight on waxed paper. In group 1, a 0.1-ml aliquot of TA was dispensed with a 30-gauge needle after shaking the vial 10 or 30 times. Group 2 used a 27-gauge needle. In group 3, the supernatant was removed from the crystals. Group 4 passed the suspension through a 0.2-microm micropore filter and rinsed the crystals with saline.


RESULTS
There was no statistically significant difference between 30- or 27-gauge needles (P = 0.83, t test) or between shaking the vial 10 or 30 times before withdrawing the drug (P = 0.99). A statistically significant difference (t test, P = 0.001) was found between TA delivered from the initial 60% of each syringe (mean +/- SD, 2.7 +/- 1.0 mg) to that drawn from the last 40% of each syringe (7.8 +/- 3.6 mg). Group 3 had a mean weight of 32.1 +/- 7.0 mg and group 4, 10.6 +/- 2.1 mg.


CONCLUSIONS
Efforts to achieve a 4.0-mg dose of TA, regardless of method used, are variable and inconsistent. Injecting through a small-gauge needle appears to concentrate the remaining suspension. Techniques to concentrate TA or remove aqueous preservatives by filtering effectively increase the concentration, but these results are variable.
Ober
Michael D
MD
Harkness Eye Institute, Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, NY, USA. obermike@gmail.com
Barile
Gaetano R
GR
Tari
Samir R
SR
Tosi
Gian Marco
GM
Tossi
Gian M
GM
Schiff
William M
WM
Chang
Stanley
S
D005374:Filtration; D005938:Glucocorticoids / Q000008:administration & dosage* / Q000737:chemistry; D007267:Injections / Q000379:methods; D014222:Triamcinolone Acetonide / Q000008:administration & dosage* / Q000737:chemistry; D014822:Vitreous Body / Q000187:drug effects
D005938:Glucocorticoids; D014222:Triamcinolone Acetonide