Incidence of weak opioids adverse events in the management of cancer pain: a double-blind comparative trial.

With the objective of comparing incidence of adverse events of the opioids codeine, hydrocodone, and tramadol in the relief of cancer pain, we conducted a randomized controlled trial in which patients with cancer were randomly assigned according to a computer-generated schedule to receive one of the three opioids. Of the 177 patients who participated, 62 patients received hydrocodone, 59 patients received codeine, and 56 patients received tramadol. The pain experienced by the participants originated most frequently from the stomach, breast, or prostate gland and was classified as either somatic (33%), visceral (52%), mixed (6%), or neuropathic (9%). At the first visit, 60% of the patients described their pain intensity as moderate (4-6/10), with the remaining 40% of the patients describing their pain as severe (7-10/10). The symptoms most associated with pain were weakness, insomnia. and anorexia. In 77% of the total number of cases, the patient was aware of his/her diagnosis prior to admittance to the palliative care unit. Of the total number of cases, 57% fell in the age range of 60-89 years old and 50% of the participants were female. No significant statistical difference in the analgesic efficacy of the three opioids was found (p: 0.69; chi(2): 0.73). Use of tramadol produced higher rates of adverse events than codeine and hydrocodone: vomiting, dizziness, loss of appetite, and weakness (p < 0.05).