[Volume calculations for current intravitreal injections of Lucentis]

Abstract

Background: Medications for blocking vascular endothelial growth factor (VEGF) are currently used for therapy of neovascular age-related macular degeneration (AMD). Some users divide the original volume of the medication Lucentis into smaller aliquots to be used for several patients. The aim of this study was to investigate whether the current original aliquot volume of Lucentis can principally be subdivided to be used for treatment two patients each with a 0.05 ml injection volume.

Materials and methods: The calculation of the dead space volume of the vessels used for injection was carried out by weighing the empty and full weights using an analytical balance. The sum of all dead space volumes was subtracted from the filling volumes. Additionally, the average extractable volume was determined from 200 original aliquots of Lucentis.

Results: Taking all necessary dead space volumes into consideration it was calculated that an extractable volume of at least 0.137 ml is necessary in order to be able to inject the necessary volume of 0.05 ml of the solution containing the active ingredient. The original volume of 0.23 ml contained in an aliquot of Lucentis cannot therefore be divided among two patients. The average extractable volume of 0.16 ml is clearly less than the full volume of 0.23 ml.

Conclusions: The original aliquots of Lucentis contain a full volume of 0.23 ml and are not suitable to be used to treat two patients. The volume can only be divided among several patients if several original aliquots are pooled and refilled. This however, presupposes a renewed filling of aliquots which represents a new potential source of contamination. Also legal aspects and the question of stability of the active ingredient have not been taken into consideration.