Randomization and blinding
Randomization was done using computer‐generated random numbers (Stat Trek software) by trained staff at the Soltan Mirahmad Clinic (Kashan, Iran). Allocation concealment was done using sequentially numbered, sealed, opaque packages. Both randomization and allocation were carried out by independent persons who were not involved elsewhere in the clinical trial. Physicians, patients, nurses responsible for referring the patients, the statistician, also the investigators who rated the patients and administered the drugs, were all blinded to the allocation. Placebo tablets were identical to NAC tablets in color, shape, size, and odor. They were all kept in identical containers and were administered by an investigational drug pharmacist.