Diclofenac in postoperative pain

Clinical bottom line

Diclofenac is an effective analgesic. A single dose administration of 50 mg had an NNT of 2.7 (2.4 to 3.1) for at least 50% pain relief over 4 to 6 hours compared with placebo in pain of moderate to severe intensity based on information from 738 patients.

Diclofenac is an NSAID, which accounted for nearly 6 million prescriptions in England in 1996.

Systematic reviews

SL Collins, RA Moore, HJ McQuay, PJ Wiffen. Oral ibuprofen and diclofenac in postoperative pain: a quantitative systematic review. European Journal of Pain 1998 2: 285-291.

SL Collins, RA Moore, HJ McQuay, PJ Wiffen, J Edwards. Single dose oral ibuprofen and diclofenac for postoperative pain. The Cochrane Library, Update Software, Oxford 2000.

Updated review prepared summer 2007, with planned publication 2008

Date review completed: October 2007
Number of trials included: 22
Number of patients: 2600
Control group: placebo
Main outcomes: 4-6 hours TOTPAR or SPID; number-needed-to-treat (NNT) for 50% pain relief (with 95% confidence intervals); relative benefit (with 95% confidence intervals).

Inclusion criteria were full journal publication of trials of diclofenac in acute postoperative pain; single oral dose; randomised; placebo-controlled; double-blind; moderate to severe baseline pain; adult populations; group sizes 10.

For each trial the mean TOTPAR or SPID values for diclofenac and placebo groups were converted to the percent of maximum total pain relief based on the categorical pain scales (%maxTOTPAR or %maxSPID). These values were then converted to dichotomous information on the proportion, and then the number of patients, who achieved at least 50%maxTOTPAR. A number-needed-to-treat for at least 50% pain relief and the relative benefit of the treatment were then calculated.

Findings

Single oral doses of diclofenac 25 mg, 50 mg and 100 mg were all significantly superior to placebo ( Table 1)..

Table 1: NNTs for diclofenac at different doses

	Number of		Percent with at least 50% pain relief
Dose (mg)	Trials	Patients	Diclofenac	Placebo	Relative benefit (95% CI)	NNT (95% CI)
25	4	502	53	15	3.6 (2.6 to 5.0)	2.6 (2.2 to 3.3)
50	12	1296	57	19	3.0 (2.5 to 3.6)	2.7 (2.4 to 3.1)
100	5	545	69	14	4.9 (3.6 to 6.6)	1.8 (1.6 to 2.1)

There was a dose response for diclofenac with higher doses producing lower (better) NNTs (Figure 1). With diclofenac 25 mg 54% of patients with initial pain of moderate or severe intensity had at least 50% pain relief over 4-6 hours, as did 63% with diclofenac 50 mg and 67% with diclofenac 100 mg.

Figure 1: Dose-response for diclofenac versus placebo

Adverse effects

Single dose oral studies showed no difference in adverse effects between diclofenac and placebo. Reported adverse effects were mild and transient. One patient withdrew after diclofenac and one after placebo in these trials.

Comment

Diclofenac at standard doses is an effective analgesic based on information from 1,300 patients for the 50 mg dose.