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Acute Pain | Chronic Pain | General

Intramuscular pethidine in postoperative pain

Clinical bottom line:

Intramuscular pethidine is an effective analgesic. A single dose of intramuscular pethidine 100 mg had an NNT of 2.9 (2.3 to 3.9) for at least 50% pain relief over 4-6 hours in patients with moderate or severe pain compared with placebo. This is similar to intramuscular morphine 10 mg which has an NNT of 2.9 (2.6-3.6). Based on small numbers of patients, pethidine 50 mg does not appear to offer effective pain relief.

Pethidine 100 mg was associated with significantly more adverse effects than placebo. The NNH for a single intramuscular dose of pethidine 100 mg was 2.6 (2.1 to 3.6).


Pethidine in postoperative pain

Pethidine is a commonly used postoperative opioid analgesic. It has similar properties to morphine, but with a more rapid onset and shorter duration of action.

Systematic review

Smith LA, Carroll D, Edwards JE, Moore RA, McQuay HJ. Single dose ketorolac and pethidine in acute postoperative pain: a systematic review. (Submitted).

Inclusion criteria were randomised, double-blind, placebo controlled trials of pethidine in postoperative pain; oral, intramuscular, intravenous administration; adult patients; baseline pain of moderate to severe intensity; pain outcome at least four hours.

Mean TOTPAR and SPID values for each trial were converted to %maxTOTPAR and %maxSPID, and then the proportion of patients achieving at least 50%maxTOTPAR were calculated. This information was used to calculate numbers-needed-to-treat and relative benefit. Adverse effects frequency data were used to calculate numbers-needed-to-harm and relative risk.

Findings

No trials of oral or intravenous pethidine met inclusion criteria.

Pethidine 50 mg

Two trials with 104 patients showed no significant benefit of pethidine over placebo, with relative benefit 1.7 (0.9 to 3.0).

Pethidine 100 mg

Eight trials of 364 patients showed significant pain relief with pethidine compared with placebo, with an NNT of 2.9 (2.3 to 3.9).

Figure: Proportion of patients in each trial achieving at least 50% pain relief with pethidine 100 mg over 4 to 6 hours compared with placebo.

(Baseline pain of at least moderate intensity).

Adverse effects

Sufficient data were available only for 100 mg doses of pethidine. Pethidine was associated with significantly more adverse effects than placebo. The NNH for a single intramuscular dose of pethidine 100 mg was 2.6 (2.1 to 3.6). The most frequently reported adverse effects were drowsiness or somnolence, dizziness or lightheadedness, and nausea or vomiting. These were significantly different compared with placebo for all but nausea and vomiting. Nine pethidine and four placebo patients withdrew from the trials due to adverse effects.

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