Carboxymethylcellulose as a new carrier substance for intravitreal injection of reproducible amounts of triamcinolone.
BACKGROUND
Intravitreal application of triamcinolone acetonide has become increasingly popular for the treatment of various retinal disorders. However, dosage, mode of preparation and application differ worldwide. The aim of this study was to find a safe vehicle that would allow intravitreal injection of an exact amount of triamcinolone acetonide without potentially retinotoxic preservatives.


METHODS
Solutions of triamcinolone acetonide with a theoretical concentration of 4 mg/0.2 ml were prepared following one sedimentation (A) and two filtration (B, C) methods. In addition, a filtration method using carboxymethylcellulose 2% as a carrier (D) was established. During processing and after injection into an eye model, the crystals were quantified by weight and high-performance liquid chromatography (HPLC), and, hence, the rate of crystal loss during this process was determined.


RESULTS
The initial preparation contained 93-106% of the calculated quantity. Method A, containing the entire vehicle, delivered 45%+/-7.3% of the target quantity to the eye model, whereas the vehicle-free methods B and C delivered 15%+/-6.9% and 11%+/-3.2%, respectively. Using carboxymethylcellulose 2% as a preservative-free vehicle, we found 93%+/-3.7% of the calculated amount in the eye model. The missing crystals were mainly sticking to the walls of the syringes and needles used for transfer.


CONCLUSIONS
Common methods for preparing triamcinolone acetonide vary in the amount of drug actually injected intravitreally. Carboxymethylcellulose is an ideal carrier substance for intravitreal application of an exact dose of triamcinolone acetonide without preservatives.
Kube
T
T
Department of Ophthalmology, University of Freiburg, Killianstrasse 5, 79106 Freiburg, Germany.
Sutter
M
M
Trittler
R
R
Feltgen
N
N
Hansen
L L
LL
Agostini
H T
HT
D002266:Carboxymethylcellulose Sodium / Q000008:administration & dosage / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004337:Drug Carriers; D005374:Filtration; D005938:Glucocorticoids / Q000008:administration & dosage / Q000737:chemistry*; D006801:Humans; D007267:Injections; D009883:Ophthalmic Solutions / Q000008:administration & dosage / Q000737:chemistry*; D004364:Pharmaceutical Preparations; D014677:Pharmaceutical Vehicles; D011310:Preservatives, Pharmaceutical; D014222:Triamcinolone Acetonide / Q000008:administration & dosage / Q000737:chemistry*; D014822:Vitreous Body
D004337:Drug Carriers; D005938:Glucocorticoids; D009883:Ophthalmic Solutions; D004364:Pharmaceutical Preparations; D014677:Pharmaceutical Vehicles; D011310:Preservatives, Pharmaceutical; D014222:Triamcinolone Acetonide; D002266:Carboxymethylcellulose Sodium