Figure 72-2 The mean and 95% confidence intervals for the number needed to treat (NNTs) are shown for several opioid analgesics from Table 72-3 . The NNTs are derived from trials investigating the efficacy of a single dose of opioid analgesic versus placebo in providing more than 50% pain relief for moderate to severe postoperative pain. The upper end of the 95% confidence interval for dihydrocodeine is actually 540.