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T. Kube, M. Sutter, L.L. Hansen, R. Trittler, R. Hauser, H.T. Agostini; Triamcinolone Acetonide Gel for Intravitreal Use . Invest. Ophthalmol. Vis. Sci. 2005;46(13):485.
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Purpose:A variety of inflammatory intraocular disorders are treated with intravitreal injection of triamcinolone acetonide. The concentration used ranges from 4 to 25 mg/0,2ml. The optimal dose is not jet known. Furthermore, there is a controversy whether the vehicle of the commercially available drug has to be eliminated due to its possible toxicity to the retina. Different preparations to clear the vehicle have been described so far: (A) Injection after sedimentation, micro–filtration via (B) three–way valve or, (C) reverse flow. Methods:Commercially available triamcinolone acetonide (Volon A) was processed according to the different preparation guidelines and the concentrate was transferred into a syringe for transportation(n=15). Each concentrate was loaded into a sterile tuberculin syringe prior to the injection into an eye–model. Concentrations of triamcinolone acetonide and benzalkonium chloride were assessed quantitatively and with high–pressure liquid chromatography (HPLC). Methyl cellulose 2% was evaluated as a new vehicle for triamcinolone acetonide crystals. Results: The concentration of triamcinolone acetonide in the transport syringes ranged in all preparations from 93±6,7% to 106±5,4% of the target concentration. Benzalkonium chloride was found in large amounts in (A), but not in (B) or (C). After injection into the eye–model, the concentration of triamcinolone acetonide was reduced to 15,4±14%(n=5), of the target concentration with preparation (B) and 11,3±12%(n=5) with preparation (C), respectively. Benzalkonium chloride was not detected. Following method (A) a concentration of 45,1±16,2%(n=5) could be measured along with large amounts of benzalkonium chloride. A significant portion of the crystalline drug was found on the inner wall of both syringes and cannulas. Methyl cellulose 2% as a new vehicle was benzalkonium chloride free, improved the rate of application to 93%(n=9) and allowed a true dosage. Conclusions:The different methods of preparations (A–C) of triamcinolone acetonide crystals for intravitreal injection produce a high rate of retrieval for the active drug. After transfer into a sterile syringe a significant portion of the crystals get lost. As a result, the final concentration of the steroid varies. Benzalkonium chloride augments the solubility of triamcinolone acetonide crystals. However, contamination with this preservative is not desired because of its assumed retinotoxic effect. Methyl cellulose 2% seems to be a novel method to deliver a definitive dose of triamcinolone acetonide gel into the eye.
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