Management of pain after abdominal surgery: dipyrone compared with pethidine

Single dose dipyrone (metamizole) for acute postoperative pain in adults

BACKGROUND

Dipyrone (metamizole) is a nonsteroidal anti-inflammatory drug used in some countries to treat pain (postoperative, colic, cancer, and migraine); it is banned in other countries because of an association with life-threatening blood disorders. This review replaces a 2010 Cochrane review that has been withdrawn.

OBJECTIVES

To assess the analgesic efficacy and associated adverse events of single dose dipyrone for moderate to severe acute postoperative pain using methods that permit comparison with other analgesics evaluated in standardised trials using almost identical methods and outcomes.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and LILACS to 11 August 2015; the Oxford Pain Relief Database; two clinical trial registries; and the reference lists of articles.

SELECTION CRITERIA

We included randomised, double-blind, placebo-controlled trials of single dose dipyrone for relief of established moderate to severe postoperative pain in adults. We accepted oral, rectal, intramuscular, and intravenous routes of administration.

DATA COLLECTION AND ANALYSIS

Two review authors independently considered studies for inclusion in the review, assessed risk of bias, and extracted data. We used summed total pain relief or pain intensity difference (TOTPAR or SPID) over four to six hours to calculate the number of participants achieving at least 50% pain relief. From derived results, we calculated the risk ratio and number needed to treat for an additional beneficial outcome (NNT), with 95% confidence intervals (CI), for one participant to experience at least 50% pain relief over four to six hours compared to placebo. We looked at use of rescue medication and time to use of rescue medication as additional measures of efficacy. We also looked for information on adverse events and withdrawals.

MAIN RESULTS

We included eight studies, involving 809 participants, comparing oral dipyrone 500 mg (143 participants), oral dipyrone 1000 mg (57 participants), and intramuscular dipyrone 2000 mg (35 participants) with placebo (236 participants). In addition to placebo, all studies used active controls (ibuprofen, paracetamol, aspirin, flurbiprofen, ketoprofen; 338 participants). Seven studies used the oral route of administration, and one study used the intramuscular route. The mean age ranged from 23 to 62 years. Six studies included both men and women, and two studies included only women. All the studies were small, but were otherwise of moderate to good quality.Over 70% of participants experienced our primary outcome of at least 50% pain relief over four to six hours with oral dipyrone 500 mg compared to 30% with placebo (five studies, 288 participants; NNT 2.4 (95% CI 1.8 to 3.1)) (moderate quality evidence). There were insufficient data to assess other doses or routes of administration of dipyrone.Fewer participants needed rescue medication within four to six hours with dipyrone 500 mg than with placebo (7% with dipyrone versus 34% with placebo; four studies, 248 participants) (low quality evidence).The data on numbers of participants experiencing any adverse event was inconsistently reported and no analysis was possible. No serious adverse events or adverse event withdrawals were reported (very low quality evidence).There were too few data to compare dipyrone directly with other active treatments.

AUTHORS' CONCLUSIONS

Based on very limited information, a single dose of dipyrone 500 mg provides good pain relief to about 70% of people treated, compared to about 30% with placebo. For every five people given dipyrone 500 mg, two people would experience this level of pain relief over four to six hours who would not have done with placebo, and fewer people would need rescue medication.We were unable to compare dipyrone directly with other active treatments, or to assess the effects of different doses or routes of administration, or the number of participants experiencing adverse events, because of insufficient data and inadequate reporting.

Metamizole-associated adverse events: a systematic review and meta-analysis

Background

Metamizole is used to treat pain in many parts of the world. Information on the safety profile of metamizole is scarce; no conclusive summary of the literature exists.

Objective

To determine whether metamizole is clinically safe compared to placebo and other analgesics.

Methods

We searched CENTRAL, MEDLINE, EMBASE, CINAHL, and several clinical trial registries. We screened the reference lists of included trials and previous systematic reviews. We included randomized controlled trials that compared the effects of metamizole, administered to adults in any form and for any indication, to other analgesics or to placebo. Two authors extracted data regarding trial design and size, indications for pain medication, patient characteristics, treatment regimens, and methodological characteristics. Adverse events (AEs), serious adverse events (SAEs), and dropouts were assessed. We conducted separate meta-analyses for each metamizole comparator, using standard inverse-variance random effects meta-analysis to pool the estimates across trials, reported as risk ratios (RRs). We calculated the DerSimonian and Laird variance estimate T² to measure heterogeneity between trials. The pre-specified primary end point was any AE during the trial period.

Results

Of the 696 potentially eligible trials, 79 trials including almost 4000 patients with short-term metamizole use of less than two weeks met our inclusion criteria. Fewer AEs were reported for metamizole compared to opioids, RR = 0.79 (confidence interval 0.79 to 0.96). We found no differences between metamizole and placebo, paracetamol and NSAIDs. Only a few SAEs were reported, with no difference between metamizole and other analgesics. No agranulocytosis or deaths were reported. Our results were limited by the mediocre overall quality of the reports.

Conclusion

For short-term use in the hospital setting, metamizole seems to be a safe choice when compared to other widely used analgesics. High-quality, adequately sized trials assessing the intermediate- and long-term safety of metamizole are needed.

WITHDRAWN: Single dose dipyrone for acute postoperative pain

BACKGROUND

Dipyrone (metamizole) is a non‐steroidal anti‐inflammatory drug used in some countries to treat pain (postoperative, colic, cancer, and migraine); it is banned in others because of an association with life‐threatening blood agranulocytosis. This review updates a 2001 Cochrane review, and no relevant new studies were identified, but additional outcomes were sought.

OBJECTIVES

To assess the efficacy and adverse events of single dose dipyrone in acute postoperative pain.

SEARCH METHODS

The earlier review searched CENTRAL, MEDLINE, EMBASE, LILACS and the Oxford Pain Relief Database to December 1999. For the update we searched CENTRAL, MEDLINE,EMBASE and LILACS to February 2010.

SELECTION CRITERIA

Single dose, randomised, double‐blind, placebo or active controlled trials of dipyrone for relief of established moderate to severe postoperative pain in adults. We included oral, rectal, intramuscular or intravenous administration of study drugs.

DATA COLLECTION AND ANALYSIS

Studies were assessed for methodological quality and data extracted by two review authors independently. Summed total pain relief over six hours (TOTPAR) was used to calculate the number of participants achieving at least 50% pain relief. Derived results were used to calculate, with 95% confidence intervals, relative benefit compared to placebo, and the number needed to treat (NNT) for one participant to experience at least 50% pain relief over six hours. Use and time to use of rescue medication were additional measures of efficacy. Information on adverse events and withdrawals was collected.

MAIN RESULTS

Fifteen studies tested mainly 500 mg oral dipyrone (173 participants), 2.5 g intravenous dipyrone (101), 2.5 g intramuscular dipyrone (99); fewer than 60 participants received any other dose. All studies used active controls (ibuprofen, paracetamol, aspirin, flurbiprofen, ketoprofen, dexketoprofen, ketorolac, pethidine, tramadol, suprofen); eight used placebo controls. Over 70% of participants experienced at least 50% pain relief over 4 to 6 hours with oral dipyrone 500 mg compared to 30% with placebo in five studies (288 participants; NNT 2.4 (1.9 to 3.2)). Fewer participants needed rescue medication with dipyrone (7%) than with placebo (34%; four studies, 248 participants). There was no difference in participants experiencing at least 50% pain relief with 2.5 g intravenous dipyrone and 100 mg intravenous tramadol (70% vs 65%; two studies, 200 participants). No serious adverse events were reported.

AUTHORS' CONCLUSIONS

Based on very limited information, single dose dipyrone 500 mg provides good pain relief to 70% of patients. For every five individuals given dipyrone 500 mg, two would experience this level of pain relief who would not have done with placebo, and fewer would need rescue medication, over 4 to 6 hours.

[The role of non-opioid analgesics in the management of postoperative pain.]

At present, intramuscular application of opioids given on request is the most widespread form of postoperative analgesia. This method is widely recognized as often being inadequate, however. As advanced techniques of pain management, such as patient-controlled analgesia, are not generally available, the question arises as to whether non-opioid analgesics should routinely be used in order to improve this situation. A review of the literature indicates that apart from when used following abdominal surgery, in particular, operations on the biliary tract, non-steroidal anti-inflammatory drugs (NSAIDS) offer effective postoperative pain control. Following minor surgery, the quality of analgesia can be better than that achieved with the weak opioids. The discrepancy between biliary tract operations and all other forms of surgery raises the question whether in the former case pain may have been partly due to spasms of visceral smooth muscle and hence be less readily amenable to the action of NSAIDS. A potential problem with the perioperative use of NSAIDS is that they inhibit platelet aggregation. Apart from tonsillectomy, there are no reports of increased intra- or postoperative bleeding when these drugs have been used for minor surgery, and only isolated reports following major operations. Despite these results, it must be borne in mind that most studies have been carried out on patients of ASA groups I and II and that conclusions drawn from the literature are not necessarily representative for the elderly and for patients with organ failure. Alternative substances have received relatively little attention. Of these, the pyrazolone derivative, metamizol, may well prove to be of value for patients in whom the use of NSAIDS is contraindicated or relatively ineffective such as after biliary tract surgery.

Single dose dipyrone for acute postoperative pain

BACKGROUND

Dipyrone (metamizole) is a non-steroidal anti-inflammatory drug used in some countries to treat pain (postoperative, colic, cancer, and migraine); it is banned in others because of an association with life-threatening blood agranulocytosis. This review updates a 2001 Cochrane review, and no relevant new studies were identified, but additional outcomes were sought.

OBJECTIVES

To assess the efficacy and adverse events of single dose dipyrone in acute postoperative pain.

SEARCH STRATEGY

The earlier review searched CENTRAL, MEDLINE, EMBASE, LILACS and the Oxford Pain Relief Database to December 1999. For the update we searched CENTRAL, MEDLINE,EMBASE and LILACS to February 2010.

SELECTION CRITERIA

Single dose, randomised, double-blind, placebo or active controlled trials of dipyrone for relief of established moderate to severe postoperative pain in adults. We included oral, rectal, intramuscular or intravenous administration of study drugs.

DATA COLLECTION AND ANALYSIS

Studies were assessed for methodological quality and data extracted by two review authors independently. Summed total pain relief over six hours (TOTPAR) was used to calculate the number of participants achieving at least 50% pain relief. Derived results were used to calculate, with 95% confidence intervals, relative benefit compared to placebo, and the number needed to treat (NNT) for one participant to experience at least 50% pain relief over six hours. Use and time to use of rescue medication were additional measures of efficacy. Information on adverse events and withdrawals was collected.

MAIN RESULTS

Fifteen studies tested mainly 500 mg oral dipyrone (173 participants), 2.5 g intravenous dipyrone (101), 2.5 g intramuscular dipyrone (99); fewer than 60 participants received any other dose. All studies used active controls (ibuprofen, paracetamol, aspirin, flurbiprofen, ketoprofen, dexketoprofen, ketorolac, pethidine, tramadol, suprofen); eight used placebo controls.Over 70% of participants experienced at least 50% pain relief over 4 to 6 hours with oral dipyrone 500 mg compared to 30% with placebo in five studies (288 participants; NNT 2.4 (1.9 to 3.2)). Fewer participants needed rescue medication with dipyrone (7%) than with placebo (34%; four studies, 248 participants). There was no difference in participants experiencing at least 50% pain relief with 2.5 g intravenous dipyrone and 100 mg intravenous tramadol (70% vs 65%; two studies, 200 participants). No serious adverse events were reported.

AUTHORS' CONCLUSIONS

Based on very limited information, single dose dipyrone 500 mg provides good pain relief to 70% of patients. For every five individuals given dipyrone 500 mg, two would experience this level of pain relief who would not have done with placebo, and fewer would need rescue medication, over 4 to 6 hours.

Dipyrone potentiates morphine-induced antinociception in dipyrone-treated and morphine-tolerant rats

Coadministration of morphine and dipyrone produces acute and chronic antinociceptive potentiation in drug-naive rats. In this work, the effectiveness of the combination was determined in rats pretreated with morphine or dipyrone. Nine groups of male rats received (i.v.) 3.1 mg/kg morphine, 600 mg/kg dipyrone, or the morphine-dipyrone combination twice a day for five administrations (three groups per treatment). From the 6th to the 10th administration, one group out of each treatment continued without change, while the other two were switched to one of the other two possible treatments. In morphine-tolerant rats, morphine plus dipyrone produced a transient antinociceptive potentiation. In dipyrone-treated animals, this combination produced a long-lasting potentiation. In animals only treated with the combination, antinociception was clear since the beginning, although it decreased after the 6th injection. No cross-tolerance was seen between morphine and dipyrone. These data suggest that dipyrone potentiates morphine-induced antinociception in dipyrone-treated as well as in morphine-tolerant rats.

Morphine and dipyrone co-administration delays tolerance development and potentiates antinociception

This work analyses the time course of tolerance development and antinociceptive potentiation throughout repeated co-administration of morphine (an opioid receptor agonist) plus dipyrone (a non-steroidal anti-inflammatory drug) in the tail-flick test. Male Wistar rats were i.v. injected with morphine (3.1 mg/kg), dipyrone (600 mg/kg) or the combination morphine/dipyrone twice a day for 5 days. Dipyrone produced antinociceptive effects with a trend towards tolerance development at the end of the treatment. Morphine was initially effective, but complete tolerance developed after its fifth administration. The combination of morphine plus dipyrone produced a significant potentiation and longer duration of antinociceptive effects. The antinociceptive efficacy of morphine and dipyrone co-administration gradually decreased after the sixth injection. An additional group of rats treated with dipyrone for 11 days developed complete tolerance after the 19th administration. These data suggest that repeated co-administration of morphine plus dipyrone results in a delay of tolerance development and in a potentiation of their individual antinociceptive effects.

Single-dose dipyrone for acute postoperative pain

BACKGROUND

The use of dipyrone as an analgesic is controversial. It is used most commonly to treat postoperative pain, colic pain, cancer pain and migraine, and in many countries, eg, Russia, Spain, Brazil, and in many parts of South-America and Africa, it is the most popular non opioid first line analgesic. In others it has been banned (e.g. USA, UK) because of its association with potentially life-threatening blood dyscrasias such as agranulocytosis. Dipyrone is currently available in Austria, Belgium, France, Germany, Italy, The Netherlands, Spain, Switzerland, South Africa, Latin America, Russia, Israel and India.

OBJECTIVES

To assess quantitatively the analgesic efficacy and adverse effects of single-dose dipyrone in randomised trials in moderate to severe postoperative pain. To compare the relative efficacy of dipyrone with other drugs assessed in the same way.

SEARCH STRATEGY

Published reports were identified from Medline, Embase, the Cochrane Library (Issue 3 1999), LILACs and the Oxford Pain Relief Database. Additional studies were identified from bibliographies of retrieved reports. Date of the most recent search: December 1999.

SELECTION CRITERIA

The following inclusion criteria were used: full journal publication, clinical trial, random allocation of patients to treatment groups, double-blind design, adult patients, pain of moderate to severe intensity at the baseline assessment, postoperative administration of study drugs, treatment arms which included dipyrone and placebo or active control and oral, rectal, intramuscular or intravenous administration of study drugs.

DATA COLLECTION AND ANALYSIS

Summed pain intensity and pain relief data over 4-6 hours were extracted and converted into dichotomous information to yield the number of patients who obtained at least 50% pain relief. This was used to calculate the proportion of patients with, and number-needed-to-treat for, at least 50% pain relief over 4-6 hours. Single-dose adverse effect data were collected.

MAIN RESULTS

Fifteen studies were included; eight used placebo and seven used an active control (oral dexketoprofen 12.5 mg or 25 mg, oral ketorolac 10 mg, intramuscular pethidine 100 mg or ketorolac 30 mg, intravenous tramadol 100 mg or rectal suprofen 300 mg). In five trials (288 patients) the mean response rate (proportion of patients with at least 50% pain relief) for single dose oral dipyrone 500 mg was 73% (range 54% to 87%) and with placebo it was 32% (19% to 41%) in moderate to severe postoperative pain over 4-6 hours. In two studies (113 patients) the response rate with oral dipyrone 1 g was 69% (61% and 77%) and with placebo it was 20% (11% and 25%). In one study (70 patients) the response rate with intramuscular dipyrone 2 g was 74% and with placebo it was 46%. No analyses could be conducted for adverse effects. The response rates in the active controlled trials were similar to those reported in the placebo controlled trials.

REVIEWER'S CONCLUSIONS

Single-dose dipyrone appears to be of similar efficacy to ibuprofen 400 mg and other analgesics frequently used in the treatment of moderate to severe postoperative pain. The commonest adverse effects were somnolence, gastric discomfort and nausea.

Metamizole: reassessment of its therapeutic role

The use of metamizole is controversial, as reflected in the very different national regulations affecting it. The striking disparities between policies for metamizole made us try to determine if there were reasons to ban, limit or liberalize its utilization. After reviewing the literature, it was concluded that metamizole should not be withdrawn from the countries where its use is still relatively free. However, metamizole causes life-threatening adverse events that are usually unpredictable and can only be prevented by better prescribing habits, so it is suggested that its use as a first-line agent should be restricted to the treatment of the pain of acute colic and circumstances in which parenteral administration of a non-narcotic agent is mandatory. Studies are needed to determine the role of second-line oral analgesics in terms of their overall toxicity and efficacy. In the meantime it is proposed that oral metamizole should be used only when other analgesics (e.g. paracetamol) have failed.

A randomized double-blind placebo-controlled study of dipyrone and aspirin in post-operative orthopaedic patients

Two hundred and fifty-four patients with post-operative pain following closed reduction of fractured long bones completed a double-blind study of dipyrone and aspirin. Compared with placebo both active treatments produced significant relief of pain, which was apparent 30 minutes after ingestion and was maintained for the 6-hour duration of the study. Dipyrone 500 mg produced significantly greater pain relief than aspirin 500 mg. Both drugs were generally well tolerated.

Pyrazolone derivatives

In many countries, the pyrazolone derivatives, which include dipyrone, antipyrine, aminopyrine and propyphenazone, are widely used analgesics. Dipyrone, the most widely used pyrazolone, has been the most studied. The pyrazolidine derivatives, phenylbutazone and oxyphenbutazone, which are not generally used for analgesia since they differ from the pyrazolones in terms of efficacy and tolerance, are not discussed in this article. Dipyrone is an inhibitor of cyclo-oxygenase but, unlike aspirin, its effect is rapidly reversible. The inhibition of prostaglandin biosynthesis contributes to the analgesic activity of the pyrazolone derivatives. Peak plasma concentrations of the pyrazolone derivatives generally occur 1 to 1.5 hours after oral administration. Half-lives vary from 1 to 2 hours with propyphenazone, to about 7 hours with dipyrone (2 hours for the active metabolite of dipyrone, 4-methylaminoantipyrine, MAA). Half-life of antipyrine varies considerably between individuals (5 to 35 hours). Unlike the NSAIDs generally, the pyrazolone derivatives antipyrine, aminopyrine and propyphenazone are minimally bound to plasma proteins. The pyrazolones undergo extensive biotransformation, aminopyrine and dipyrone being converted to active metabolites. Dipyrone is the only drug for which results of recent double-blind trials are available. Oral dipyrone has been shown to be more effective than an equal dose of aspirin or paracetamol in alleviating postoperative pain, and intravenous dipyrone 2.5g was similar in efficacy to pethidine 50 mg. In patients with acute ureteral or biliary colic, dipyrone 2.5g intravenously was similar in efficacy to indomethacin 50 mg or pethidine 50 mg. The most frequently reported side effects of the pyrazolone derivatives are skin rashes. Gastrointestinal side effects are rare. Blood dyscrasias, mostly associated with aminopyrine, have received wide attention in the medical literature, but their true incidence with dipyrone is considerably lower than the often quoted incidence for amidopyrine reported more than 30 years ago.

Use of antipyretic analgesics in the pediatric patient

Fever and pain are the most common issues in pediatric patient management. Acetaminophen, aspirin, and dipyrone are the most commonly used drugs and are equivalent in their efficacy. Dipyrone, used in many parts of the world, but not in the United States, is an effective agent; however, it has been implicated in producing agranulocytosis and anaphylactic shock. The salicylates have anti-inflammatory effects making them appropriate for the treatment of patients with juvenile rheumatoid arthritis, but they are gastric irritants, may impair clotting, and, because of saturable kinetics, may lead to accumulation and toxicity. Acetaminophen is an effective antipyretic and analgesic with few side effects that is toxic only in massive overdose.

Postoperative analgesics for superficial surgery. Comparison of four analgesics

The efficacy of mild analgesics after 160 various superficial operations was studied by comparing intravenous lysine-acetylsalicylate (LAS) 1.8 g, Litalgin 4 ml (metamizole = dipyrone 2.0 g+ pitophenone 8.0 mg) or paracetamol 0.5 g to oxycodone 4 mg. At 15 min postdrug, oxycodone 4 mg had the best peak effect but this significant (P less than 0.05) difference to mild analgesics disappeared at 30 min, and thereafter all test analgesics showed an equally low effect. Two-thirds of the patients anaesthetized without peroperative analgesics needed pain relief when recovering from superficial surgery. The need for pain relief was lowest after varicose vein operations 40% of the patients as compared to about 70% after other types of superficial surgery. In 42% of the patients requiring pain relief, the test analgesics alone gave sufficient pain relief. The rest needed an additional 5 mg of oxycodone, on average, to be comfortable. The combined use of mild analgesics and oxycodone for adequate pain relief did not seem to reduce the postdrug sedation as compared to oxycodone alone. The results indicate that in traditional clinical dosages LAS, dipyrone or paracetamol can substitute about 5 mg oxycodone but offer sufficient analgesia only in about 40% of the patients recovering from superficial surgery.