title: Measurement of the actual dose of triamcinolone acetonide delivered by common techniques of intravitreal injection.
abstract: 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.
authors.affiliation: Harkness Eye Institute, Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, NY, USA. obermike@gmail.com
authors.forename: Michael D
authors.initials: MD
authors.lastname: Ober
authors.forename: Gaetano R
authors.initials: GR
authors.lastname: Barile
authors.forename: Samir R
authors.initials: SR
authors.lastname: Tari
authors.forename: Gian Marco
authors.initials: GM
authors.lastname: Tosi
authors.forename: Gian M
authors.initials: GM
authors.lastname: Tossi
authors.forename: William M
authors.initials: WM
authors.lastname: Schiff
authors.forename: Stanley
authors.initials: S
authors.lastname: Chang
mesh_terms: 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
chemical_list: D005938:Glucocorticoids; D014222:Triamcinolone Acetonide