Original sentence: Its duration of clinical effect is 120-150 minutes although it is typically administered in 4-6 hour intervals.Pethidine has been shown to be less effective than morphine, diamorphine or hydromorphone at easing severe pain, or pain associated with movement or coughing
Edited sentence: Despite producing analgesia for 2-3 hours at most, pethidine is typically administered at 4-6 hour intervals, so that the patient spends at least an hour (and up to four hours) between doses without any analgesia, resulting in much unnecessary pain and suffering.In addition, pethidine has been shown to be less effective than morphine, diamorphine or hydromorphone at easing severe pain, or pain associated with movement or coughing.Its duration of clinical effect is 120-150 minutes