Comparison of a traditional paracetamol medication and a new paracetamol/paracetamol-methionine ester combination

Analgesic effect of oral ibuprofen 400, 600, and 800 mg; paracetamol 500 and 1000 mg; and paracetamol 1000 mg plus 60 mg codeine in acute postoperative pain: a single-dose, randomized, placebo-controlled, and double-blind study

PURPOSE

Effect size estimates of analgesic drugs can be misleading. Ibuprofen (400 mg, 600 mg, 800 mg), paracetamol (1000 mg, 500 mg), paracetamol 1000 mg/codeine 60 mg, and placebo were investigated to establish the multidimensional pharmacodynamic profiles of each drug on acute pain with calculated effect size estimates.

METHODS

A randomized, double-blind, single-dose, placebo-controlled, parallel-group, single-centre, outpatient, and single-dose study used 350 patients (mean age 25 year, range 18 to 30 years) of homogenous ethnicity after third molar surgery. Primary outcome was sum pain intensity over 6 h. Secondary outcomes were time to analgesic onset, duration of analgesia, time to rescue drug intake, number of patients taking rescue drug, sum pain intensity difference, maximum pain intensity difference, time to maximum pain intensity difference, number needed to treat values, adverse effects, overall drug assessment as patient-reported outcome measure (PROM), and the effect size estimates NNT and NNTp.

RESULTS

Ibuprofen doses above 400 mg do not significantly increase analgesic effect. Paracetamol has a very flat analgesic dose-response profile. Paracetamol 1000/codeine 60 mg gives similar analgesia as ibuprofen from 400 mg, but has a shorter time to analgesic onset. Active drugs show no significant difference in maximal analgesic effect. Other secondary outcomes support these findings. The frequencies of adverse effects were low, mild to moderate in all active groups. NNT and NTTp values did not coincide well with PROMs.

CONCLUSION

Ibuprofen doses above 400 mg for acute pain offer limited analgesic gain. Paracetamol 1000 mg/codeine 60 mg is comparable to ibuprofen doses from 400 mg. Calculated effect size estimates and PROM in our study seem not to relate well as clinical analgesic efficacy estimators.

TRIAL REGISTRATION

NCT00699114.

Increase in volume of lignocaine/adrenaline-containing local anaesthetic solution causes increase in acute postoperative pain after gingivectomy

A randomized, single-blind, within-patient, crossover study was done in 44 patients (27 women and 17 men mean age 47 years, range 29-63) who had bilateral 'identical' gingivectomies. On one occasion a standard volume of local anaesthetic containing lignocaine 2% and adrenaline (1/80 000) was infiltrated into the mucosal tissue before operation. On the other occasion double the standard volume was infiltrated. The intensity of pain postoperatively was recorded by the patients on 100 mm visual analogue scale every hour for an 11-hour observation period. The intensity of pain when double volume had been given was significantly higher than that after the standard volume from 2 to 8 hours postoperatively (P < 0.04), the median (range) being 52.0 mm (0.0-434.0) compared with 30.5 mm (0.0-359.0) after the standard volume (P < 0.005). Doubling the volume of local anaesthetic containing adrenaline that was infiltrated increased the intensity of acute pain after gingivectomy.

The effect of paracetamol or diclofenac administered before operation on postoperative pain and behaviour after adenoidectomy in small children

We compared the effects of rectally administered diclofenac (12.5 mg) with paracetamol (125 mg) on pre- and postoperative behaviour and the need for supplementary analgesia in 44 children scheduled for adenoidectomy (with or without myringotomy). The study drugs were given in combination with diazepam (0.5 mg.kg-1) about 20 min before the children were taken to the operating theatre. On arrival there, the children who had received diclofenac were significantly quieter (< 0.05), easier to handle (p < 0.01) and cried less (p < 0.05) than those in the paracetamol group. During recovery, children in the diclofenac group needed fewer supplementary doses of intravenous pethidine than those receiving paracetamol (p < 0.001). There were no obvious differences between the groups in intra-operative bleeding (as estimated by the surgeon), or in measured blood loss. No postoperative complications became evident. The pre-operative rectal administration of diclofenac for pain relief after adenotomy is safe and effective.

Properties of the radicals formed by one-electron oxidation of acetaminophen--a pulse radiolysis study

The semi-iminoquinone radical of acetaminophen, which has previously been proposed as a possible hepatotoxic intermediate in the cytochrome P-450 catalysed oxidation of acetaminophen, has been generated and studied by pulse radiolysis. In the absence of other reactive solutes, the radical decays rapidly by second order kinetics with a rate constant (2k2) of (2.2 +/- 0.4) x 10(9) M-1 sec-1. In alkaline solutions the radical deprotonates with a pK of 11.1 +/- 0.1 to form a radical-anion, as confirmed by the effect of ionic strength on the rate of radical decay. The acetaminophen radical-anion reacts with resorcinol at high pH values, leading to the formation of a transient equilibrium from which the one-electron reduction potential of the semi-iminoquinone radical of acetaminophen is estimated to be +0.707 +/- 0.01 V at pH 7. This value predicts that acetaminophen should be oxidised by thiyl radicals. This was confirmed by pulse radiolysis experiments for reaction of the cysteinyl radical, for which rate constants of 7 x 10(6) M-1 sec-1 at pH 7 and 2.7 x 10(8) M-1 sec-1 at pH 11.3 were obtained. The reaction of O2 with the acetaminophen semi-iminoquinone radical could not be detected by pulse radiolysis, and alternative mechanisms for superoxide radical formation are discussed.

A new paracetamol/paracetamol-methionine ester combination effects on postoperative course

The SUR2647 combination is a sachet formulation containing free paracetamol and its N-acetyl-methionate ester (SUR2647). In a randomized, single-blind, within-patient study the effect of the SUR2647 combination on the postoperative course was investigated in 30 out-patients after bilateral oral surgery. On one occasion they received sachets of SUR2647 combination 2 b.i.d. (equivalent to 2 g paracetamol X 2) on the day of operation, and one sachet b.i.d. (equivalent to 1 g paracetamol X 2) on the following two days. On the other occasion they received placebo caplets. The observed mean reduction in swelling on the third (16%) and seventh (34%) postoperative days after receiving active drug was not significantly different as compared to placebo, nor was there a significant difference between the two treatments with respect to oral temperature, mouth-opening capability or postoperative bleeding. Pain after the SUR2647 combination regime was significantly lower (P less than 0.01) than placebo until the second postoperative evening. Complaints were registered in both treatment groups, although reports of mild to moderate drowsiness were more common after the SUR2647 combination.