Salazopyrin is another drug for ulcerative colitis but can cause liver abnormalities.
"The pharmacist did not speak directly to the woman when she inquired with a shop assistant about the change from Pentasa as he mistakenly believed she was querying the change from Lipitor," the commissioner's office said.
The woman took the drugs, began feeling extremely tired and took time off work. A blood test revealed abnormalities and her GP learned she had been taking Salazopyrin for about three weeks. She was admitted to hospital with a primary diagnosis of deranged liver function and the overall opinion was that her condition was caused by a reaction to the drug.
Meanwhile, a nurse at an accident clinic has been criticised for failing to assess an elderly woman who had been vomiting blood and was later found to have stomach ulcers.
The 72-year-old woman - who had had spinal surgery without complications two days earlier - was taken to the clinic between 8pm and 8.30pm by her daughter, after first bringing up blood at home at 8pm.
Commissioner Anthony Hill's report on the case found the registered nurse (RN) told the daughter to call an ambulance for her mother to be taken to hospital.
"The RN considered that the woman required hospital treatment, and that a personal call would achieve a priority response from the ambulance service, rather than if the clinic contacted the ambulance for her.
"The RN did not triage the woman, take a history or undertake an initial assessment of her."
The daughter phoned 111 on her cellphone from inside the clinic and then waited with her mother, who was lying down in the back of the daughter's car in the carpark. An ambulance arrived at 8.42pm and took the woman to hospital, where she was diagnosed with multiple stomach ulcers.
Mr Hill found the nurse had breached the code of patients' rights by failing to assess the woman and failing to facilitate a safe transfer to hospital.
He said the nurse should have contacted the ambulance service or made sure the clinic did so. The nurse ought to have ensured the woman was monitored; it was wrong to leave the woman without medical oversight.
The nurse has apologised to the patient and her daughter. Mr Hill recommended the nurse be taught how to communicate effectively.