When using mesalazine, urine can turn red-brown after contact with bleach (chlorine) in the toilet bowl. Side Effects Center Lareb received 21 reports of this.
Mesalazine is a medicine for the treatment of chronic intestinal inflammation, such as Crohn’s disease and ulcerative colitis. It inhibits inflammation in the intestinal wall.
Pale
The callers indicated that the urine discolored when the urine entered toilet bowls that had been cleaned with bleach. This also happened if the bleach had already been flushed. Sometimes the discolouration could no longer be removed from the toilet or from the toilet seat. The red-brown discoloration does not occur with cleaning agents without bleach.
Innocent
The red-brown urine is harmless. It is important to keep in mind that red-brown urine can also indicate kidney problems. But then the urine is already discolored when urinating and not only when the urine comes into contact with bleach in the toilet.
Action
Lareb has informed the Medicines Evaluation Board (MEB) about this. The subject is being further investigated in a European context. Based on this, the European Medicines Agency (EMA) decides whether an adjustment of the package leaflet is necessary.
View the overview of the notifications here (in English).