British journal of clinical pharmacology
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Br J Clin Pharmacol · Oct 1980
Randomized Controlled Trial Clinical TrialMethodological considerations in the evaluation of analgesic combinations: acetaminophen (paracetamol) and hydrocodone in postpartum pain.
1 In a double-blind study, 108 postpartum patients received single oral doses of either placebo, acetaminophen (paracetamol) 1000 mg, hydrocodone 10 mg, the combination of acetaminophen plus hydrocodone, or codeine 60 mg. 2 In the 2X2 factorial analysis, both the acetaminophen and hydrocodone effects were statistically significant, whereas the interaction contrast was not. This indicates that the analgesic effect of the combination represents the additive effect of its constituents and is consistent with the assumption that these constituents are producing analgesia by different mechanisms. 3 Although significantly superior to placebo, codeine seemed to be inferior to the other treatments. 4 Compared with placebo, both codeine and hydrocodone (centrally acting narcotics) seemed relatively more effective in uterine cramp than episiotomy pain; the reverse seemed true with acetaminophen (a peripherally acting analgesic). 5 Some methodological implications for the evaluation of analgesic combinations are discussed.
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1 The intensity of postoperative pain is influenced by many factors, for example, individual variation, site of incision and type of operation, anaesthetic technique, and the interval from the end of operation to the appearance of pain. 2 These factors affect the efficacy of analgesics. 3 Mild analgesics provide adequate pain relief in half of our patients in the immediate postoperative phase when the pain is slight to moderate. 4 The maximum effect of mild analgesics corresponds to that produced by morphine 6-10 mg. Adequate analgesia may not therefore be provided for the treatment of severe postoperative pain unless narcotic analgesics have been used peroperatively. 5 When mild analgesics are combined with narcotics synergism is achieved. 6 As postoperative pain decreases with time, mild analgesics usually provide adequate pain relief on the first and following postoperative days.