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Acute Pain | Chronic Pain | General

Intravenous and intramuscular parecoxib for postoperative pain

Clinical bottom line

Parecoxib is an effective analgesic in acute pain. The NNT for parecoxib 20 mg IV for at least 50% pain relief over six hours was 3.0 (95% confidence interval 2.3 to 4.1), for parecoxib 40 mg IV the NNT was 2.2 (1.8 to 2.7). The weighted mean remedication time was 1.6 hours for placebo (125 patients), 5.6 hours for parecoxib 20 mg IV (170 patients), 8.7 hours for parecoxib 40 mg IV (173 patients) and 5.5 hours for ketorolac 30 mg IV (121 patients).


Parecoxib is a prodrug of valdecoxib, a selective inhibitor of cyclooxygenase 2 (COX 2) administered as an intramuscular or intravenous injection. Traditionally oral NSAIDs such as ibuprofen and diclofenac are used to treat mild to moderate acute pain, however, this may be problematic when patients are unable to take oral medication or are nauseous and vomiting. Trials in dental, gynaecologic and orthopaedic pain suggest that parecoxib is efficacious and well tolerated. The aim of this systematic review was to pool appropriate data in a meaningful way and quantify efficacy and adverse effects alongside other analgesic options.

Systematic review


J Barden, JE Edwards, HJ McQuay, RA Moore. Oral valdecoxib and injected parecoxib for acute postoperative pain: a quantitative systematic review BMC Anesthesiology 2003, 3:1 . (http://www.biomedcentral.com/1471-2253/3/1).

Inclusion criteria were single intramuscular or intravenous dose, randomised, placebo-controlled, double blind trials of parecoxib in acute postoperative pain with sufficient data to calculate the area under the curve for pain relief (TOTPAR). Baseline pain was moderate to severe. The 6 hour TOTPAR was calculated for each patient, and the data were converted to the percent of maximum total pain relief from categorical pain scales (%maxTOTPAR), and then to dichotomous information to generate a number-needed-to-treat for at least 50% pain relief. Relative benefit was calculated to provide an assessment of how much more likely an individual given a particular treatment is to have at least 50% pain relief than someone given no treatment. Adverse effects frequency data were used to calculate numbers-needed-to-harm and relative risk.

Findings

There were four placebo-controlled trials included, and the details and references are shown in a downloadable PDF ( Table 1 ). Over 35 other studies and abstracts were excluded as they failed to meet the inclusion criteria. All included trials also included active comparators (ketorolac 30 mg, ketorolac 60 mg and morphine 4 mg).

All trials showed statistical benefit of parecoxib 20 mg IV and 40 mg IV over placebo (Figure 1 & Figure 2). One trial also showed statistical benefit of parecoxib 20 mg IM and 40 mg IM over placebo. Overall 85/170 patients (50%) given parecoxib 20 mg IV experienced at least 50% maxTOTPAR over six hours compared with 29/176 patients (16%) with placebo, the NNT for one patient to have at least half pain relief over six hours was 3.0 (2.3 to 4.1).

Figure 1: Individual trials with parecoxib 20 mg IV

Figure 2: Individual trials with parecoxib 40 mg IV

For parecoxib 40 mg IV, 109/173 patients (63%) experienced at least 50% maxTOTPAR over six hours, the NNT for one patient to have at least half pain relief over six hours with was 2.3 (2.0 to 2.6). The NNTs for both doses given intramuscularly were lower (better) however patient numbers were too few for surety (Table 2).

Table 2:

Number (%) of patients with at least 50% pain relief

Drug and dose

Number of trials

Parecoxib

Placebo

Relative benefit
(95% CI)

NNT
(95% CI)

Parecoxib 20 mg IV

4

85/170
(50)

29/176
(16)

3.1 (2.2 to 4.5)

3.0 (2.3 to 4.1)

Parecoxib 20 mg IM

1

32/51
(63)

2/51
(4)

16 (4.1 to 63.3)

1.7 (1.4 to 2.3)

Parecoxib 40 mg IV

4

109/173
(63)

29/176
(16)

3.8 (2.7 to 5.5)

2.2 (1.8 to 2.7)

Parecoxib 40 mg IM

1

39/50
(78)

2/51
(4)

19.9 (5.1 to 78)

1.4 (1.2 to 1.6)

The median time to remedication was given in the four studies. For placebo the weighted mean time to remedication from 125 patients was 1.6 hours. For parecoxib 20 mg IV the weighted mean time to remedication based on 170 patients was 5.6 hours, on balance with ketorolac 30 mg IV (5.5 hours based on 121 patients). For parecoxib 40 mg IV the weighted mean time to remedication from 173 patients was 8.7 hours (Figure 3).

Figure 3: Weighted mean time to remedication

Adverse events

Three trial reports included the proportion of patients experiencing different adverse events. An adverse event of some type was reported by 55% (73/132) of patients on placebo, 65% (86/132) of patients on parecoxib 20 mg IV and 55% (73/132) of patients on parecoxib 40 mg IV. Pooled analyses of available data for headache, nausea and vomiting revealed no significant differences between either dose of parecoxib IV and placebo. There were no reports of adverse reactions or irritation at injection site.

Comment

So far the amount of evidence for paracoxib IV and IM is limited, but compares favbourably with the number of patients included in reviews of ketorolac 30 mg IM (359) and pethidine 100 mg IM (364), though is smaller than the number available for morphine 10 mg IM (946). The results are encouraging, and it is particularly interesting to see that time to remedication is being reported.