Implanted catheters are locked with a solution comprising a lower alcohol, typically ethanol, propanol, or butanol, in a range from 1% to 99% by volume, and an additive in a range from 1% to 99% by volume, the additive comprising an anti-microbial, typically taurolidine or triclosan, or an anti-coagulant, typically riboflavin, sodium citrate, ethylene diamine tetraacetic acid, or citric acid. The use of an alcohol and additive solution can effectively reduce fouling of the catheter, particularly clotting and thrombus in intravascular catheters, as well as eradicate existing infections and/or reduce the risk of potential infections. Existing infections and/or potential infections can be further reduced by employing a catheter body which permits an anti-microbial solution to penetrate into the catheter body and preferably through the catheter into tissue surrounding the implanted catheter.