IRCT201201258778N3.

Methods	Double‐blind RCT. Design: parallel. Duration: 4 weeks. Location: single centre (Children Medical Center, Tehran).
Participants	Inclusion criteria: children with CF aged between 4 and 18 years of age; either gender; pancreatic insufficient ; no NSAIDs for 2 weeks prior to enrolment. Exclusion criteria: younger than 4 years of age; pancreatic sufficient; used NSAIDs during 2 weeks prior to enrolment. Target sample size: 25.
Interventions	Intervention: protexin 2 sachet per day which can be mixed with yoghurt. Placebo: maltodextrin 2 sachet per day which can be mixed in yoghurt.
Outcomes	Change in fecal calprotectin at 1 month.
Notes	Funding source: drug and placebo send by manufacturer free of charge and no payment to the Tehran Medical University for running the trial. Contact: A/Professor Dr Farzaneh Motamed, Pediatric Gasteroentrologist, Children Medical Center, 62 Gharib St, 14194 Tehran, Iran (fmotamed@sina.tums.ac.ir).