Catheters used for medical treatment, e.g., hemodialysis are filled with a locking solution, usually heparin between treatments. To prevent infections, antimicrobial or antibiotic substances have been used as locking solution alone or in combination with antithrombotic substances. It has been found that these locking solutions are rapidly washed out from the catheter tip. The invention describes a thixotropic gel that can be used as locking solution. Beneficial, substances, e.g., antimicrobial or antibiotic substances can be added to the gel. A preferred antimicrobial substance is taurolidin alone or in combination with salicylic acid or one of its salts.
