This invention relates to compositions , methods, devices and kits relatingto the Infusion of a catheter lock Solution into an indwelling catheter. Inventivecompositions, methods, devices and kits aid in diminishing the effects of microbialinfection in catheters and occlusion of the catheters. A lock Solution providedby the invention includes citrate and a paraben. The Solution preferably hasa density suitable for retention of the Solution in a catheter during the lockperiod. Another lock Solution provided by the invention includes citrate, aparaben and a photo-oxidant, such as, for example, methylene blue.