In the present two-arm, parallel design, double-blind randomized controlled clinical trial, volunteer ulcerative colitis patients who referred to the inflammatory bowel disease (IBD) clinic of Imam Reza hospital, belongs to the Tabriz University of medical sciences were enrolled. The patients were diagnosed previously based on standard diagnostic criteria including characteristic endoscopic and histological appearances. The patients were included if they aged 18-75 years of age, have pancolitis and treated with a high dose of prednisolone (1 mg/kg), and achieved clinical remission. The pregnant and breastfeeding patients, the patients with heart, renal and pulmonary failure, and the ones who use anti-TNF-α agents were ineligible.
One hundred ninety-eight patients with active ulcerative colitis were treated with prednisolone 1 mg/kg and Mesalamine 4 g/day for four weeks. One hundred seventy-five volunteer patients with clinical responses at the end of week 4 consent to participate in the study. The patients were randomized using a computer-generated randomization chart. The patients in the intervention group (n=82) were supplemented with 400 mg NAC twice daily and the patients in the placebo group (n=86) were received the placebo for 16 weeks. Simultaneously, prednisolone dose was tapered by 5 mg/week to a daily dose of 20 mg/day, then slow the taper to 2.5 mg/week until prednisolone is discontinued (14 weeks).
NAC was purchased from Hexal, Germany. NAC and placebo were labeled as A and B administered by a researcher who was not part of the data collection or analysis. The appearance and characteristics of the NAC and placebo were identical. The patients and the outcome an assessor were blind to group assignment.
Full written consent was obtained from all subjects. The study had the approval of the Tabriz University of medical sciences Ethics Committee (Ethics code: IR.TBZMED.REC.1398.408). This trial was registered at the Iranian registry of clinical trials (irct.ir). Identifier NO. IRCT20190713044185N1.
The sample size was calculated based on the result of a previous study that revealed that the clinical response in the NAC group was higher (66%) than the placebo group (44%). By assuming a two-sided significance level of 1% and power of 80% with equal allocation to the two arms, we needed 80 patients in each arm of the trial. To allow for dropout, 87 patients recruited per arm.
The patients were visited every two weeks during the intervention (16 weeks) and followed up six more weeks post-intervention. In all visits, full blood count, fecal calprotectin, erythrocyte sedimentation rate (ESR), and high sensitive C-reactive protein (hs-CRP) levels were checked. Additionally, the relevant questionnaire for calculation of disease severity using partial mayo score was completed. The combined scores of rectal bleeding (0-3), stool frequency (0-3), and physician’s global assessment (0-3) were used for calculation of partial mayo score (0-9). According to partial mayo score, the total score of <2 was considered as remission, 2-5 as a mild activity, 5-7 as moderate activity, and >7 as a severe activity. In addition, at last visit, the endoscopic Mayo score was also calculated by an expert gastroenterologist-endoscopist (0 to 3).
Assessment of compliance was a predefined analysis whereby patients taking >80% of their prescribed study medication were considered compliant. Compliance with study medication was calculated by pill count every two weeks.
Evaluation of the therapeutic efficacy
The primary efficacy of the treatment was remaining in remission. Clinical relapse was defined as exacerbation of symptoms with a partial Mayo score of ≥ 3, or modification of treatment [dose escalation, the addition of steroids, tacrolimus, topical formulations, or biologics] accompanied by worsening of symptoms. The secondary outcomes were the endoscopic relapse (endoscopic score of >1), serum level of hs-CRP, hemoglobin, and fecal calprotectin level.
Assessment of safety
The hematological and biochemical studies including liver function tests (LFT), blood urea nitrogen (BUN), and creatinine were performed at regular intervals by the analytical laboratory services of the corresponding hospital. Moreover, a treating physician who was blind to the patients’ treatment assignments evaluated the adverse effects including nausea, vomiting, diarrhea, constipation, drowsiness, chest pain, and skin rash.
SPSS version 21 was used for statistical analysis. The normality of data distribution was analyzed using the Kolmogorov-Smirnov test. The continuous data were presented as mean and standard deviations and the categorical data were present as number and frequency. The chi-square test (for nominal variable) and independent t-test (for continuous variable) were used for comparison of the baseline characteristics. One-way analysis of covariance (ANCOVA) was used for comparison of the follow-up characteristics with adjusting for age, sex, disease duration, and baseline values. Time to relapse was analyzed by Kaplan–Meier methodology and measured from the date of the first dose of study medication to the relapse date. Treatment differences were analyzed using a log-rank test. Intention-to-treat (ITT) analysis was done and p-value of less than 0.05 was considered as significant.