Metamizole: reassessment of its therapeutic role

Pharmacological treatment of cancer pain and opioid induced nausea and vomiting: online survey and comparison with current guidelines

PURPOSE

We assumed that in Palliative Care, even in common clinical situations, the choice of drugs differs substantially between physicians. Therefore, we assessed the practice of pharmaceutical treatment choices of physicians for cancer pain and opioid-induced nausea and vomiting (OINV) and the rationale for their choices.

METHODS

An online survey was conducted with physicians covering the following domains: i) Cancer pain therapy: non-opioids in addition to opioids: choice of drug ii) prevention of OINV: choice of drug and mode of application. Current guidelines concerning cancer pain therapy and prevention of OINV were compared.

RESULTS

Two-hundred-forty European physicians responded to our survey. i) Use of non-opioids in addition to opioids for the treatment of cancer pain: Only 1.3% (n = 3) of respondents never used an additional non-opioid. Others mostly used: dipyrone/metamizole (49.2%, n = 118), paracetamol/acetaminophen (34.2%, n = 82), ibuprofen / other NSAIDs (11.3%, n = 27), specific Cox2-inhibitors (2.1%, n = 5), Aspirin (0.4%, n = 1), no answer (2.9%, n = 7). ii) Antiemetics to prevent OINV: The drugs of choice were metoclopramide (58.3%, n = 140), haloperidol (26.3%, n = 63), 5-HT3 antagonists (9.6%, n = 23), antihistamines (1.3%, n = 3) and other (2.9%, n = 7); no answer (1.7%, n = 4). Most respondents prescribed the substances on-demand (59.6%, n = 143) while others (36.3%, n = 87) provided them as around the clock medication. Over both domains, most physicians answered that their choices were not based on solid evidence from randomized controlled trials (RCTs). Guidelines were inconsistent regarding if and what non-opioid to use for cancer pain and recommend anti-dopaminergic drugs for prevention or treatment of OINV.

CONCLUSIONS

Physician's practice in palliative care for the treatment of cancer pain and OINV differed substantially. Respondents expressed the lack of high-quality evidence- based information from RCTs. We call for evidence from methodologically high-quality RCTs to be available to inform physicians about the benefits and harms of pharmacological treatments for common symptoms in palliative care.

Construction of Highly Functionalized C4-Oxyacylated and Aminated Pyrazolines

Pyrazolines and pyrazolones are prevalent cores in drugs and bioactive molecules. Functionalizing them with heteroatoms on the ring improves or expands their clinical efficacy. However, a general method to selectively heterofunctionalize them at C4 and C5 is still elusive. Herein, we have demonstrated an iodine(III)-mediated construction of C4-heterofunctionalized pyrazolines from α,β-unsaturated hydrazones. The oxyacylated and aminated products, bearing a tertiary as well as a secondary stereocenter, were obtained via aza-Michael, followed by a C-O/C-N bond formation. A deprotection/oxidation sequence produced pyrazolones in a quantitative yield.

Evaluation of the effect of tramadol, paracetamol and metamizole on the severity of experimental colitis

Application of dextran sodium sulfate (DSS) is often used to induce experimental colitis. Current state of the art is to refrain from the use of analgesics due to their possible interaction with the model. However, the use of analgesics would be beneficial to reduce the overall constraint imposed on the animals. Here, we analyzed the effect of the analgesics Dafalgan (paracetamol), Tramal (tramadol) and Novalgin (metamizole) on DSS-induced colitis. To study the effect of those analgesics in colitis mouse models, acute and chronic colitis was induced in female C57BL6 mice by DSS administration in the drinking water. Analgesics were added to the drinking water on days four to seven (acute colitis) or on days six to nine of each DSS cycle (chronic colitis). Tramadol and paracetamol had minor effects on colitis severity. Tramadol reduced water uptake and activity levels slightly, while mice receiving paracetamol presented with a better overall appearance. Metamizole, however, significantly reduced water uptake, resulting in pronounced weight loss. In conclusion, our experiments show that tramadol and paracetamol are viable options for the use in DSS-induced colitis models. However, paracetamol seems to be slightly more favorable since it promoted the overall wellbeing of the animals upon DSS administration without interfering with typical readouts of colitis severity.

Real world evidence of the use of metamizole (dipyrone) by the Brazilian population. A retrospective cohort with over 380,000 patients

Objective

To determine under which health conditions metamizole (dipyrone) is used as a single drug or as fixed-dose combination.

Methods

Two retrospective cohorts of Brazilian patients treated with metamizole between January 2015 and December 2017 were analyzed: a metamizole-based cohort (Cohort 1) and a symptoms-based cohort (Cohort 2). Anonymized patient data was obtained from Amil Clinical Data Warehouse. The number of patients with symptoms was described by age and sex.

Results

The sample size of the two cohorts consisted of 384,668 patients. In patients using metamizole (Cohort 1), the most common reason for medication was the treatment of some form of pain (81%), followed by fever (19%). Headache was the most common (19%) specified pain class, followed by sore throat (8%), muscular pain (6%), and abdominal pain (5%). In adult patients (n=276,279; 71.8%), metamizole was used as a monotherapy or associated with another drug, for any sort of pain, in over 88% of the patients. General pain was the main reason for metamizole use in children (61%).

Conclusion

Real world evidence to evaluate Brazilian patients’ therapeutic options is unusual and yet to be more explored using digital tools enabling better data registration. The present study confirmed that metamizole is widely used as a non-anti-inflammatory drug, and also showed the management of pain and fever as the most frequent indications in all age groups studied.

Registry in Clinical Trials Database: REBEC Database: 10507

Quality appraisal of existing guidelines for the management of headache disorders by the AGREE II's method

OBJECTIVE

To evaluate the quality of existing clinical practice guidelines for headache management and their main recommendations.

BACKGROUND

Evidence-based clinical practice guidelines have been developed to support the clinical decision-making. However, to achieve this goal, the quality of these guidelines must be ensured.

METHODS

A systematic search for clinical practice guidelines for headache management was conducted in the PubMed database, in websites of known guideline developers and in websites of known headache associations. The quality appraisal was performed through the Appraisal of Guidelines for Research and Evaluation II method.

RESULTS

Twelve guidelines were evaluated. The domains of rigor of development, applicability, and editorial independence, which most influence the overall quality of guidelines, had the lowest average scores and the highest standard deviation rates (61% ± 23; 37% ± 20; 53% ± 31). The main recommendations regarding medication use for acute treatment of episodic tension-type headache and migraine in adult patients consisted of paracetamol, acetylsalicylic acid, and other nonsteroidal anti-inflammatory drugs in all guidelines.

CONCLUSIONS

The statistical results indicate that the appraised guidelines have room for both individual and collective improvement. In addition, there is a well-established medication recommendation pattern among all guidelines evaluated.

Antinociceptive Synergy Between Metamizole and Hesperidin in a Model of Visceral Pain in Mice

BACKGROUND

Metamizole is used to relieve the visceral pain but its adverse effects limit its use. An alternative to improve its efficacy with lower doses is to combine it with a natural product as hesperidin.

AIM OF THE STUDY

The aim of this study was to evaluate the antinociceptive interaction between metamizole and hesperidin in a visceral pain model using an isobolographic analysis.

METHODS

Antinociception was evaluated in the writhing model using acetic acid (1%) to induce writhes in mice. Metamizole (1-316 mg/kg), hesperidin (3-300 mg/kg), or combinations with a fixed-dose ratio of 1:1 were administered intraperitoneally 30 min before the acetic acid and the number of writhes was counted for 30 min. Isobolographic analysis was employed to define the nature of the compound interaction.

RESULTS

Metamizole and hesperidin in individual administration induced dose-dependent antinociceptive effects, reached an efficacy of 84.2 ± 5.9% and 66.3 ± 7.4%, respectively. The ED₅₀ values calculated from their dose-response curves were 84.5 ± 22.7 and 108.9 ± 17.9 mg/kg, respectively. The analysis of DRC for the metamizole + hesperidin combination, in a ratio 1:1 showed a ED_{50 COMB} value lower than the ED_{50 ADD} estimated from the additivity line from the isobologram (46.7 ± 6.3 vs. 96.7 ± 11.9 mg/kg, respectively). In addition, the pharmacological interaction calculated was of 0.48. These results suggest a synergistic interaction for the antinociceptive activity of metamizole + hesperidin combination.

CONCLUSION

These data suggest that metamizole + hesperidin combination could be useful in treating visceral pain as it can interact synergistically using low dose of both drugs with the possibility of reducing the risk of adverse effects.

Genome-Wide Association Study of Metamizole-Induced Agranulocytosis in European Populations

Agranulocytosis is a rare yet severe idiosyncratic adverse drug reaction to metamizole, an analgesic widely used in countries such as Switzerland and Germany. Notably, an underlying mechanism has not yet been fully elucidated and no predictive factors are known to identify at-risk patients. With the aim to identify genetic susceptibility variants to metamizole-induced agranulocytosis (MIA) and neutropenia (MIN), we conducted a retrospective multi-center collaboration including cases and controls from three European populations. Association analyses were performed using genome-wide genotyping data from a Swiss cohort (45 cases, 191 controls) followed by replication in two independent European cohorts (41 cases, 273 controls) and a joint discovery meta-analysis. No genome-wide significant associations (p < 1 × 10⁻⁷) were observed in the Swiss cohort or in the joint meta-analysis, and no candidate genes suggesting an immune-mediated mechanism were identified. In the joint meta-analysis of MIA cases across all cohorts, two candidate loci on chromosome 9 were identified, rs55898176 (OR = 4.01, 95%CI: 2.41–6.68, p = 1.01 × 10⁻⁷) and rs4427239 (OR = 5.47, 95%CI: 2.81–10.65, p = 5.75 × 10⁻⁷), of which the latter is located in the SVEP1 gene previously implicated in hematopoiesis. This first genome-wide association study for MIA identified suggestive associations with biological plausibility that may be used as a stepping-stone for post-GWAS analyses to gain further insight into the mechanism underlying MIA.

High-Throughput Sequencing to Investigate Associations Between HLA Genes and Metamizole-Induced Agranulocytosis

Background and Objective: Agranulocytosis is a rare and potentially life-threatening complication of metamizole (dipyrone) intake that is characterized by a loss of circulating neutrophil granulocytes. While the mechanism underlying this adverse drug reaction is not well understood, involvement of the immune system has been suggested. In addition, associations between genetic variants in the Human Leukocyte Antigen (HLA) region and agranulocytosis induced by other drugs have been reported. The aim of the present study was to assess whether genetic variants in classical HLA genes are associated with the susceptibility to metamizole-induced agranulocytosis (MIA) in a European population by targeted resequencing of eight HLA genes.

Design: A case-control cohort of Swiss patients with a history of neutropenia or agranulocytosis associated with metamizole exposure (n = 53), metamizole-tolerant (n = 39) and unexposed controls (n = 161) was recruited for this study. A high-throughput resequencing (HTS) and high-resolution typing method was used to sequence and analyze eight HLA loci in a discovery subset of this cohort (n = 31 cases, n = 38 controls). Identified candidate alleles were investigated in the full Swiss cohort as well as in two independent cohorts from Germany and Spain using HLA imputation from genome-wide SNP array data. In addition, variant calling based on HTS data was performed in the discovery subset for the class I genes HLA-A, -B, and -C using the HLA-specific mapper hla-mapper.

Results: Eight candidate alleles (p < 0.05) were identified in the discovery subset, of which HLA-C^∗04:01 was associated with MIA in the full Swiss cohort (p < 0.01) restricted to agranulocytosis (ANC < 0.5 × 10⁹/L) cases. However, no candidate allele showed a consistent association in the Swiss, German and Spanish cohorts. Analysis of individual sequence variants in class I genes produced consistent results with HLA typing but did not reveal additional small nucleotide variants associated with MIA.

Conclusion: Our results do not support an HLA-restricted T cell-mediated immune mechanism for MIA. However, we established an efficient high-resolution (three-field) eight-locus HTS HLA resequencing method to interrogate the HLA region and demonstrated the feasibility of its application to pharmacogenetic studies.

Reactive Metamizole Metabolites Enhance the Toxicity of Hemin on the ATP Pool in HL60 Cells by Inhibition of Glycolysis

Metamizole is an analgesic, whose pharmacological and toxicological properties are attributed to N-methyl-aminoantipyrine (MAA), its major metabolite. In the presence of heme iron, MAA forms reactive metabolites, which are toxic for granulocyte precursors. Since decreased cellular ATP is characteristic for MAA-associated toxicity, we studied the effect of MAA with and without hemin on energy metabolism of HL60 cells, a granulocyte precursor cell line. The combination MAA/hemin depleted the cellular ATP stronger than hemin alone, whereas MAA alone was not toxic. This decrease in cellular ATP was observed before plasma membrane integrity impairment. MAA/hemin and hemin did not affect the proton leak but increased the maximal oxygen consumption by HL60 cells. This effect was reversed by addition of the radical scavenger N-acetylcysteine. The mitochondrial copy number was not affected by MAA/hemin or hemin. Hemin increased mitochondrial superoxide generation, which was not accentuated by MAA. MAA decreased cellular ROS accumulation in the presence of hemin. In cells cultured in galactose (favoring mitochondrial ATP generation), MAA/hemin had less effect on the cellular ATP and plasma membrane integrity than in glucose. MAA/hemin impaired glycolysis more than hemin or MAA alone, and N-acetylcysteine blunted this effect of MAA/hemin. MAA/hemin decreased protein expression of pyruvate kinase more than hemin or MAA alone. In conclusion, cellular ATP depletion appears to be an important mechanism of MAA/hemin toxicity on HL60 cells. MAA itself is not toxic on HL60 cells up to 100 µM but boosts the inhibitory effect of hemin on glycolysis through the formation of reactive metabolites.

Acute intermittent porphyria: analgesia can be dangerous

Acute intermittent porphyria (AIP) is a rare condition, a metabolic disorder of the haem biosynthesis. An acute crisis of AIP can present as a combination of symptoms, such as abdominal pain, autonomic dysfunction, hyponatremia, muscle weakness and neurological symptoms in the absence of others obvious causes. We report the case of a 53-year-old woman, who was previously diagnosed with AIP 5 weeks after therapeutic suspension has developed an acute disease exacerbation. During hospitalisation, further exacerbation has occurred after analgesia with metamizole. Glucose and hemin infusions resulted in slow improvement. Physical rehabilitation was crucial to peripheral polyneuropathy recovery. Taking into account the porphyrinogenic effect described for metamizole, this drug might have triggered the second attack. Clinical history was sufficient to suspect the diagnosis and to start the treatment immediately, preventing important sequelae.

Dose reduction, oral application, and order of intake to preserve aspirin antiplatelet effects in dipyrone co-medicated chronic artery disease patients

BACKGROUND

Dipyrone comedication in aspirin-treated patients is associated with impaired pharmacodynamic response to aspirin (high on-treatment platelet reactivity [HTPR]). Additionally, in small observational studies, an association with impaired outcome has been described. In this uncontrolled, hypothesis-generating study, we aimed to investigate strategies to prevent this drug-drug interaction in patients with coronary artery disease (CAD).

METHODS

We analyzed pharmacodynamic response to aspirin in 80 dipyrone co-medicated CAD patients. Aspirin antiplatelet effects were measured using arachidonic acid (AA)-induced light-transmission aggregometry (LTA). Platelet reactivity was associated with daily dose, administration form, and frequency. Additionally, we conducted a time-series analysis in patients with HTPR to aspirin with re-evaluation of pharmacodynamic response to aspirin after 5 days.

RESULTS

Patients' mean age was 75.5 ± 9.8 years. Forty-three (54%) were male, 22 (27.5%) obese, and 38 (47.5%) diabetics. Baseline characteristics, cardiovascular risk factors, comorbidities, comedication, or laboratory parameters did not differ between patients with or without HTPR. HTPR to aspirin occurred in 34 out of 80 patients (42.5%). The incidence of HTPR was associated with dipyrone daily dose (< 1 g/day: HTPR 20% vs. > 3 g/day: HTPR 50%, p > 0.0001) and form of administration (i.v. 87.5% vs. oral 37.5%; p < 0.0001). A strict order of intake (aspirin 30 min prior to dipyrone) restored aspirin antiplatelet effects in all patients (HTPR before 100% vs. HTPR after 0%, p = 0.0002).

CONCLUSION

This study shows that dipyrone should be used with caution in aspirin-treated patients. If dipyrone seems indispensable, the lowest effective dose and a strict order of intake seem favorable.

Safety of metamizole: a systematic review of the literature

WHAT IS KNOWN AND OBJECTIVE

Metamizole was withdrawn from the market in the United States and several European countries following reports of fatal agranulocytosis among users, but is still available in many countries in Europe, South America and Asia. Over the past several decades, a number of epidemiologic studies have been conducted to quantify the risk of agranulocytosis and other adverse effects associated with metamizole and other non-narcotic analgesics. The objective of this study was to perform a systematic review of the safety of metamizole.

METHODS

Epidemiologic studies published between 1 January 1980 and 15 December 2014 were identified through systematic searches of PubMed and Google Scholar; the reference sections of selected articles were also reviewed to identify potentially relevant studies. Studies included in this review focused on the safety of metamizole, that is on outcomes such as haematologic abnormalities, gastrointestinal bleeding, anaphylaxis and hepatotoxicity. Two study investigators independently reviewed the abstracts and articles to determine relevant studies according to prespecified criteria.

RESULTS AND DISCUSSION

A total of 22 articles met the criteria for evaluation. The majority of studies that evaluated agranulocytosis indicated an increased risk associated with metamizole, with relative risk (RR) estimates ranging from 1·5 (95% CI, 0·8-2·7) to 40·2 (95% CI, 14·7-113·3). Findings of three case-control studies do not suggest an association between metamizole and aplastic anaemia. Of the five case-control studies that evaluated the risk of upper gastrointestinal bleeding, four found a statistically significant increased risk associated with metamizole (RR estimates ranging from 1·4 to 2·7). There is insufficient evidence to determine whether metamizole increases the risk of other outcomes (e.g. hepatic effects, anaphylaxis, congenital anomalies). Few studies evaluated the effects of dose, route of administration or duration of therapy.

WHAT IS NEW AND CONCLUSION

Published studies reported differences in the magnitude of risk of adverse outcomes associated with metamizole use and often had small sample sizes and a number of other limitations that may have biased the results. Further research is needed to better quantify the potential risks associated with metamizole compared to other non-narcotic analgesics.

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.

Analysis of non-steroidal anti-inflammatory drug use in hospitalized patients and perception of their risk

Non-steroidal anti-inflammatory drugs (NSAIDs) belong to the most widely prescribed and used pharmacological agents worldwide. Data gathered in the last decade show increased incidence of thrombotic events during NSAID administration. Analysis of NSAID usage and assessment of risk for development of cardiovascular adverse effects is needed for improving patient safety. For limiting the impact of adverse effects on the health of patients, NSAID users should be informed about the possible adverse effects and their symptoms to ensure early detection and treatment discontinuation. In the presented study, we retrospectively analyzed the administration of NSAIDs in a group of patients (n=428) in need of analgesic treatment hospitalized at a department of internal medicine. Factors increasing the risk for cardiovascular adverse effects were also investigated. A separate questionnaire study was conducted to gather information concerning the knowledge of hospitalized NSAID users (n=251) about adverse effects of the medication used. For purpose of comparison, we conducted a similar study in a group of 234 random respondents from a shopping center. Data were evaluated using descriptive statistics, Student's t-test and chi-squared test. Our results suggest that the majority of patients treated with NSAIDs have factors indicating increased risk of development of adverse effects, most commonly arterial hypertension (58.2% of patients). The results of our questionnaire study show limited knowledge of NSAID users about the risk of the therapy. Nearly half of the respondents were unaware of any adverse effects. We consider as alarming that only a limited number of respondents were informed by their physician or pharmacist about the possible risks of treatment. In conclusion, we found that hospitalized NSAID users often have a history of diseases predisposing to the development of cardiovascular adverse effects of NSAIDs. Despite this, their knowledge about the risk of treatment is insufficient.

Pharmacological characteristics of metamizole

Metamizole (dipyrone) is a popular analgetic, non-opioid drug, commonly used in human and veterinary medicine. In some cases, this agent is still incorrectly classified as a non-steroidal anti-inflammatory drug (NSAID). Metamizole is a pro-drug, which spontaneously breaks down after oral administration to structurally related pyrazolone compounds. Apart from its analgesic effect, the medication is an antipyretic and spasmolytic agent. The mechanism responsible for the analgesic effect is a complex one, and most probably rests on the inhibition of a central cyclooxygenase-3 and activation of the opioidergic system and cannabinoid system. Metamizole can block both PG-dependent and PG-independent pathways of fever induced by LPS, which suggests that this drug has a profile of antipyretic action distinctly different from that of NSAIDs. The mechanism responsible for the spasmolytic effect of metamizole is associated with the inhibited release of intracellular Ca2+ as a result of the reduced synthesis of inositol phosphate. Metamizole is predominantly applied in the therapy of pain of different etiology, of spastic conditions, especially affecting the digestive tract, and of fever refractory to other treatments. Co-administration of morphine and metamizole produces superadditive, antinociceptive effects. Metamizole is a relatively safe pharmaceutical preparation although it is not completely free from undesirable effects. Among these side-effects, the most serious one that raises most controversy is the myelotoxic effect. It seems that in the past the risk of metamizole- induced agranulocytosis was exaggerated. Despite the evidence showing no risk of teratogenic and embryotoxic effects, the drug must not be administered to pregnant women, although it is allowed to be given to pregnant and lactating animals. This paper seeks to describe the characteristics of metamizole in the light of current knowledge.

Life-threatening agranulocytosis, anemia, and plasmacytosis after dipyrone use for fever in a child

Dipyrone or metamizole Na (Novalgin) is commonly used as an antipyretic, analgesic, and spasmolytic agent in some parts of the world; however, it is banned in developed countries because of severe side effects. Here we present a case of a 4-year-old boy who developed life-threatening agranulocytosis, anemia, and marked plasmacytosis in his bone marrow after dipyrone use for fever, which resolved with steroid therapy.

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.

Rapid clinical induction of bupropion hydroxylation by metamizole in healthy Chinese men

AIMS

This study aimed to investigate the effect of metamizole on bupropion hydroxylation related to different CYP2B6 genotype groups in healthy volunteers.

METHODS

Sixteen healthy male volunteers (6 CYP2B6*1/*1, 6 CYP2B6*1/*6 and 4 CYP2B6*6/*6) received orally administered bupropion alone and during daily treatment with metamizole 1500 mg day(-1) (500 mg tablet taken three times daily) for 4 days. Serial blood samples were obtained up to 48 h after each bupropion dose.

RESULTS

After metamizole treatment relative to bupropion alone, the geometric mean ratios (GMRs) and 90% confidence interval (CI) of the AUC(0,∞) ratio of 4-hydroxybupropion over bupropion were 1.99 (1.57, 2.55) for the CYP2B6*1/*1 group, 2.15 (1.53, 3.05) for the CYP2B6*1/*6 group and 1.86 (1.36, 2.57) for the CYP2B6*6/*6 group. The GMRs and 90% CI of bupropion were 0.695 (0.622, 0.774) for AUC(0,∞) and 0.400 (0.353, 0.449) for C(max) , respectively. The corresponding values for 4-hydroxybupropion were 1.43 (1.28, 1.53) and 2.63 (2.07, 2.92). The t(1/2) value was significantly increased for bupropion and decreased for 4-hydroxybupropion. The t(max) values of bupropion and 4-hydroxybupropion were both significantly decreased. The mean percentage changes in pharmacokinetic parameters among the CYP2B6 genotype groups were not significantly different.

CONCLUSIONS

Oral administration of metamizole for 4 days significantly altered the pharmacokinetics of both bupropion and its active metabolite, 4-hydroxybupropion, and significantly increased the CYP2B6-catalyzed bupropion hydroxylation in all of the subjects. Cautions should be taken when metamizole is co-administered with CYP2B6 substrate drugs.

Dipyrone inhibits neuronal cell death and diminishes hypoxic/ischemic brain injury

BACKGROUND

Dipyrone is an analgesic and antipyretic drug usually prescribed for patients with inflammatory conditions. We recently identified dipyrone as an antiapoptotic agent by screening a library of 1040 compounds for their ability to inhibit cytochrome c release from isolated mitochondria.

OBJECTIVE

We investigated the potential neuroprotective properties of dipyrone in cerebral ischemia.

METHODS

We evaluated the protective effects of dipyrone in experimental models of neuronal hypoxia/ischemia, including an oxygen/glucose deprivation model in primary cerebrocortical neurons and a focal cerebral ischemia model in mice.

RESULTS

Dipyrone reduced hypoxia/ischemia injury in both cellular and animal models. Dipyrone inhibited the release of cytochrome c and other mitochondrial apoptogenic factors from mitochondria into the cytoplasm, and attenuated subsequent caspase-9 and caspase-3 activation both in vitro and in vivo. Moreover, dipyrone prevented ischemia-induced changes in Bcl-2 and tBid, and ameliorated oxygen/glucose deprivation-mediated loss of mitochondrial membrane potential. Dipyrone also inhibited ischemia-induced reactive microgliosis. In the cellular models evaluated, dipyrone did not inhibit oxygen/glucose deprivation-induced cyclooxygenase-2 activation.

CONCLUSION

Dipyrone is remarkably neuroprotective in cerebral ischemia, and its cyclooxygenase-independent protective properties are, at least in part, due to the inhibition of mitochondrial cell death cascades.

Qualidade de medicamentos isentos de prescrição: um estudo com marcas de dipirona comercializadas em uma drogaria de Cascavel (PR, Brasil)

A dipirona é um fármaco muito utilizado pela população brasileira. É considerado seguro mesmo em gestantes, lactentes e crianças, mas é proibido em alguns países do mundo pelo suposto papel de causar agranulocitose e anemia aplástica. Em 2001, a Agência Nacional de Vigilância Sanitária (Anvisa) considerou que os medicamentos com esse fármaco apresentavam bom risco-benefício em relação a outros de indicação semelhante. Porém, de nada adianta segurança no uso de um medicamento se este é de baixa qualidade. É comum encontrar no mercado brasileiro medicamentos fora dos padrões, o que se constitui em um risco para a população em geral. Dessa forma, foram analisadas sete amostras de marcas diferentes de dipirona solução oral comercializados em uma farmácia de Cascavel (PR). Os resultados demonstram que a fiscalização quanto à qualidade de medicamentos similares precisa ser aprimorada, pois eles foram os que mais apresentaram desvios de qualidade.

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.

Update on the Incidence of Metamizole Sodium-Induced Blood Dyscrasias in Poland

Metamizole sodium (metamizole) is a popular non-opioid analgesic and a common non-prescription product in Poland. Controversy exists regarding the level of risk of agranulocytosis or aplastic anaemia associated with its use. Two previous pharmacovigilance studies conducted in Poland found the risk was low. Twenty-four of the 25 haematology centres that provide specialist care for the 30 million adults in Poland participated in this prospective 12-month study. Twenty-one cases of agranulocytosis, 48 of aplastic anaemia, 15 of neutropenia and 11 of pancytopenia were reported. Of these cases, three (two agranulocytosis; one aplastic anaemia) were judged as being possibly related to metamizole. Crude estimates of the rate of agranulocytosis and aplastic anaemia associated with metamizole were 0.16 and 0.08 cases/million person-days of use, respectively. Ongoing national safety surveillance in Poland shows that, despite the possibility of drug-induced blood dyscrasias with metamizole, the risk is very low.

Intravenous paracetamol (acetaminophen)

Intravenous paracetamol (rINN)/intravenous acetaminophen (USAN) is an analgesic and antipyretic agent, recommended worldwide as a first-line agent for the treatment of pain and fever in adults and children. In double-blind clinical trials, single or multiple doses of intravenous paracetamol 1 g generally provided significantly better analgesic efficacy than placebo treatment (as determined by primary efficacy endpoints) in adult patients who had undergone dental, orthopaedic or gynaecological surgery. Furthermore, where evaluated, intravenous paracetamol 1 g generally showed similar analgesic efficacy to a bioequivalent dose of propacetamol, and a reduced need for opioid rescue medication. In paediatric surgical patients, recommended doses of intravenous paracetamol 15 mg/kg were not significantly different from propacetamol 30 mg/kg for the treatment of pain, and showed equivocal analgesic efficacy compared with intramuscular pethidine 1 mg/kg in several randomized, active comparator-controlled studies. In a randomized, noninferiority study in paediatric patients with an infection-induced fever, intravenous paracetamol 15 mg/kg treatment was shown to be no less effective than propacetamol 30 mg/kg in terms of antipyretic efficacy. Intravenous paracetamol was well tolerated in clinical trials, having a tolerability profile similar to placebo. Additionally, adverse reactions emerging from the use of the intravenous formulation of paracetamol are extremely rare (<1/10 000). [table: see text].

Clinical equivalence of IV paracetamol compared to IV dipyrone for postoperative analgesia after surgery for breast cancer

OBJECTIVE

To assess clinical efficacy of IV paracetamol 1 g and IV dipyrone 1 g on a 24-h dosing schedule in this randomised, double-blinded study of 40 ASA I-III (American Society of Anesthesiologists classification of physical status) patients undergoing surgery for breast cancer.

RESEARCH DESIGN AND METHODS

General anaesthesia using remifentanil and propofol was performed for surgery. The patients were randomly allocated to two groups, receiving infusions of paracetamol 1 g/100 mL (Para Group) or of dipyrone 1 g/100 mL (Dipy Group) 30 min before arrival in the recovery area and every 6 h up to 24 h postoperatively. All patients had unrestricted access to opioid rescue medication via an IV patient-controlled analgesia (PCA) device.

MAIN OUTCOME MEASURES

The primary variables for clinical equivalence were the differences between the mean values for pain scores at rest and pain scores on coughing over 30 h postoperatively. The equivalence margin was determined as +/-10 mm on the visual analogue scale (VAS).

RESULTS

Regarding pain scores at rest, the 90% CI of the mean differences between the treatment groups over 30 h postoperatively was found to be within the predefined equivalence margin [+7.5/-6.2], and the CI values for pain scores on coughing [+7.3/-9.0] were similar. The two groups did not differ in cumulative opioid rescue consumption (Dipy-Group 14.8 +/- 17.7 mg vs. Para Group 12.1 +/- 8.8 mg, p = 0.54) nor in piritramide loading dose (Dipy Group 0.95 +/- 2.8 mg vs. Para Group 1.3 +/- 2.8 mg, p = 0.545). Five patients in the Dipy Group experienced hypotension in contrast to none in the Para Group (p = 0.047). There were no significant between-treatment differences for other adverse events, patient satisfaction scores (p = 0.4) or quality of recovery scores (p = 0.3).

CONCLUSION

IV paracetamol 1 g is clinically equivalent to IV dipyrone 1 g for postoperative analgesia after surgery for breast cancer.

Characterization of oxalic acid derivatives as new metabolites of metamizol (dipyrone) in incubated hen's egg and human

Metamizol (dipyrone, 1), a widely used drug with effective analgesic and antispasmodic properties, shows severe side effects like agranulocytosis and anaphylactic shock reactions, the reasons of which are not known until today. After oral administration 1 is completely metabolized. All hitherto known metabolites have an intact pyrazolinone ring structure like the parent compound and are completely extractable from urine with polar organic solvents. However, only a fractional amount of the applied dosage can be recovered by this procedure. To clarify the reason of this deficit of unknown metabolites we followed the hypothesis of oxidative rupture of the heterocyclic ring during metabolism of 1. On the basis of former in vitro results we now were able to identify in quality three oxalic acid derivatives and one acetic acid phenylhydrazide as new metabolites of metamizol in the allantoic fluid (AF) of incubated hen's eggs as well as in human urine by means of GC-MS analysis and comparison with unequivocally synthesized authentic reference compounds. Whereas the oxamazide 7, the phenylhydrazide 8 and N-methyloxamic acid 9 are only present in trace concentrations and therefore cannot account for the deficit in the balance of metabolites, the oxalic acid monohydrazide 11 seems to be excreted in higher amount. But quantitative determination of this new metabolite would be required to answer the open questions concerning the biotransformation of metamizol and thereby to detect new facts about mode of action and side effects of this drug.

A comparison between IV paracetamol and IV metamizol for postoperative analgesia after retinal surgery

OBJECTIVE

To assess clinical efficacy of IV paracetamol 1 g and IV metamizol 1 IV metamizol 1 g on a 24-h dosing schedule in this randomized, double-blinded, placebo-controlled study of 38 ASA physical status I-III patients undergoing retinal surgery.

RESEARCH DESIGN AND METHODS

General anaesthesia using remifentanil, propofol, and desflurane was performed for surgery. The patients were randomly allocated to three groups, receiving infusions of paracetamol 1 g/100 mL (Para Group), of metamizol 1 g/100 mL (Meta Group), or of 100 mL of saline solution as placebo control (Plac Group) 30 min before arrival in the recovery area and every 6 h up to 24 h postoperatively. All patients had unrestricted access to intravenous opioid rescue medication.

MAIN OUTCOME MEASURES

The primary efficacy variables were pain scores at rest over 30 h postoperatively analysed by using repeated ANOVA measurement. Secondary efficacy variables were pain scores on coughing, also analysed by repeated ANOVA measurement.

RESULTS

Five patients in the Plac Group and one patient in the Meta Group interrupted the study protocol. Regarding pain scores at rest, Mauchly-test of sphericity was significant (p = 0.03). For the p time effects a significant result was detected (p < 0.001). The main effect between the three treatment groups was significantly different (p = 0.01). The Bonferroni adjusted pair wise comparisons between p the Plac Group and the Para Group showed a significant difference in favour of IV paracetamol (p = 0.024; mean difference 14.8; p 95% CI 1.6-28.0), between the Plac Group and the Meta Group in favour of IV metamizol (p = 0.025; mean difference 14.4; 95% CI p 1.5-27.4), and no significant difference between the Para Group and the Meta Group (p = 1.0; mean difference 0.4; 95% CI-12.8 to 13.6). Pain scores on coughing showed a significant different main effect between the three treatment groups (p = 0.022). The Bonferroni adjusted pair wise comparisons between the Plac Group and the Para Group showed a significant difference in favour of IV paracetamol (p = 0.032; mean difference 17.9; 95% CI 1.3-34.6), a p difference, though not reaching statistical significance, in favour of IV metamizol between the Plac Group and the Meta Group (p = 0.081; p mean difference 15.0; 95% CI -1.4 to 31.4), and no significant difference between the Para Group and the Meta Group (p = 1.0; p mean difference 2.9; 95% CI -13.8 6 to 19.6). None of the patients experienced itching; one patient in the Meta Group developed a mild erythema. There was no statistical difference in the incidence of nausea (Plac vs. Para Group: p = 0.94, Plac vs. Meta Group: p = 0.98, Para vs Meta Group: p = 0.95) or vomiting (Plac vs. Para Group: p = 0.73, Plac vs. Meta Group: p = 0.85, Para vs Meta Group: p = 0.86) between the groups. Patients in the Plac Group experienced significantly more often sedation than patients in the Meta Group (p = 0.049). There was a trend of higher sedation in the Plac Group than in the Para Group, which did not reach statistical significance (p = 0.07). There was no difference in sedation between the Meta and the Para Groups (p = 0.84).

CONCLUSION

IV paracetamol 1 g has a similar analgesic potency as IV metamizol 1 g for postoperative analgesia after retinal surgery.

Alpha 2-adrenoceptors and 5-HT receptors mediate the antinociceptive effect of new pyrazolines, but not of dipyrone

In this study, we investigated whether spinal noradrenergic and serotonergic systems are involved in the antinociception induced by the novel pyrazolines 3-methyl- and 3-phenyl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-1-pyrazole-1-carboxyamide (MPCA and PPCA, respectively), and the pyrazolinone dipyrone in the acetic acid writhing (stretching) test in mice. Intrathecal (i.t.) administration of methysergide (3 and 10 microg) and yohimbine (3 microg), but not of prazosin (0.3 and 1 microg) prevented the antinociceptive action of MPCA and PPCA (500 micromol/kg, s.c.). Dipyrone-induced antinociception (500 micromol/kg, s.c.) was not affected by methysergide or adrenoceptor antagonists. These results suggest that spinal 5-HT receptors and alpha2-adrenoceptors are involved in the antinociception induced by MPCA and PPCA, but not in that elicited by dipyrone.

Allergic cholestatic hepatitis and exanthema induced by metamizole: verification by lymphocyte transformation test

We report about a 66-year-old-male patient who was hospitalized with generalized exanthema and increase of liver enzymes after intake of metamizole because of flue-like symptoms. Despite initial high dose steroids, disease activity persisted, and therefore liver biopsy was performed. Histology revealed acute hepatitis with perivenular non-bridging confluent necrosis and granuloma formation consistent with drug-induced hepatitis. A metamizole-induced process was suspected. Lymphocyte transformation test confirmed the sensitization of the patient's lymphocytes to metamizole and three of its four metabolites (4-methylaminoantipyrine, 4-acetylaminoantipyrine and 4-formylaminoantipyrine). Other drugs could be excluded with high probability. In the follow-up, the general condition of the patient improved, and liver enzymes decreased under treatment with steroids. Thus, we conclude that in this patient metamizole has induced an allergic reaction not only of the skin but also of the liver. To our knowledge, an allergic cholestatic hepatitis caused by metamizole has been reported only once in literature.

Hypothermic and antipyretic effects of 3-methyl- and 3-phenyl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-pyrazole-1-carboxyamides in mice

The effect of novel pyrazolines, 3-methyl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-pyrazole-1-carboxyamide (MPCA) and 3-phenyl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-pyrazole-1-carboxyamide (PPCA) on body temperature and endotoxin-induced fever was investigated in mice. The subcutaneous (s.c.) administration of 1.5 mmol/kg dipyrone, MPCA or PPCA and the intracerebroventricular (i.c.v.) administration of 225 nmol dipyrone reduced basal rectal temperature. Intracerebroventricular administration of 225 nmol MPCA or PPCA did not alter basal rectal temperature. The administration of 0.15 mmol/kg (s.c.) or 25 nmol (5 microl) dipyrone (i.c.v.), MPCA or PPCA had no effect on basal rectal temperature, but reversed lipopolysaccharide-induced fever. These results suggest that MPCA and PPCA cause antipyresis, which is similar to that caused by dipyrone, and may be useful antipyretic agents.

The incidence of metamizole sodium-induced agranulocytosis in Poland

Metamizole sodium continues to be used extensively as an analgesic in Poland. This study was the first undertaken to quantify the incidence of agranulocytosis associated with metamizole sodium in Poland, and to compare the findings with those from other countries. Based on data obtained retrospectively from medical records covering the period 1997-2001 in six haematology centres representative of Poland as a whole, the crude estimate obtained was a rate of 0.2 cases per million person-days of use. This is the same order of magnitude as the value from an epidemiological study covering several countries (0.3-4.0).

Single dose dipyrone for acute renal colic pain

BACKGROUND

Renal colic pain is extremely painful and requires immediate treatment with strong analgesics. Dipyrone is the most popular non-opioid first line analgesic in many countries but in others it has been banned (e.g. USA, UK) because of its association with blood dyscrasias such as agranulocytosis. Since dipyrone is used in many countries (e.g. Brazil, Spain) there is a need to determine the benefits and harms of its use to treat renal colic pain.

OBJECTIVES

To assess quantitatively the analgesic efficacy and adverse effects of single-dose dipyrone in adults with moderate to severe renal colic pain.

SEARCH STRATEGY

Published reports were identified from electronic databases (MEDLINE, EMBASE, the Cochrane Library, LILACS) and additional studies were identified from the reference lists of retrieved reports. Date of the most recent search: January 2000.

SELECTION CRITERIA

Inclusion criteria were: full journal publication; RCT with a double-blind design; adult patients with baseline renal colic pain of moderate or severe intensity; treatment arms which included dipyrone (oral, intramuscular or intravenous administration) and a control; single dose data.

DATA COLLECTION AND ANALYSIS

Summed pain intensity and pain relief data were extracted and converted into dichotomous information to yield the number of patients with at least 50% pain relief over 15-30 minutes, 1-2 hours and six hours. The proportion of patients with at least 50% pain relief was calculated. Single dose adverse effect data were collected.

MAIN RESULTS

Eleven studies with 1053 patients (550 on dipyrone) met the inclusion criteria. Unfortunately, few data were available for analysis; most analyses were based on the results of single, small trials and statistical pooling of the results was inappropriate. Efficacy estimates were calculated as the weighted mean percent of patients achieving at least 50% pain relief with the range of values from trials contributing to the analysis. However, these estimates were not robust. Commonly reported adverse effects with intravenous dipyrone were dry mouth and somnolence, and one study reported pain at the injection site. Insufficient information was available for safety analyses to be conducted.

REVIEWER'S CONCLUSIONS

Limited available data indicated that single dose dipyrone was of similar efficacy to other analgesics used in renal colic pain, although intramuscular dipyrone was less effective than diclofenac 75 mg. Combining dipyrone with antispasmolytic agents did not appear to improve its efficacy. Intravenous dipyrone was more effective than intramuscular dipyrone. Dry mouth and somnolence were commonly reported with intravenous dipyrone. None of the studies reported agranulocytosis.

Intravenous metamizol (Dipyrone) in acute migraine treatment and in episodic tension-type headache--a placebo-controlled study

Acute headache is a very frequent symptom, responsible for significant demand at primary care units and emergency rooms. In such sets in Brazil, metamizol is easily found but, on the other hand, neither ergotics nor triptans are available. The aim of this study is to compare intravenous metamizol with placebo in the acute treatment of migraine with aura, migraine without aura and episodic tension-type headache. Fifty-four migraine with aura patients, 95 migraine without aura patients and 30 tension-type headache patients were treated with metamizol. Ninety patients (30 migraine with aura, 30 migraine without aura and 30 tension-type headache patients) received placebo. Pain intensity, nausea, aura, photo- and phonophobia were investigated at 30 min and 60 min after the administration of the drug. Significant improvement of pain after 30 min and 60 min post-dosage was achieved from metamizol groups compared with placebo groups. Significant improvement of all other symptoms was achieved after 60 min post-dosage. Side-effects were mild and with small incidence. Metamizol is an effective, safe and low price drug. It may be regarded as a good alternative drug for the treatment of common acute primary headaches.

The effect of a single intravenous dose of metamizol 2 g, ketorolac 30 mg and propacetamol 1 g on haemodynamic parameters and postoperative pain after heart surgery

Although nonopiate analgesics may be particularly useful in the immediate postoperative period after major surgery, their use has been associated with haemodynamic adverse effects during postoperative pain treatment and in critically ill patients in intensive care. The effect of a single intravenous dose of metamizol (dipyrone) 2 g, ketorolac 30 mg and propacetamol 1 g on haemodynamic variables and pain control in the immediate postoperative period after heart surgery is compared. Seventy-two patients undergoing elective coronary and/or heart valve surgery, were included in a cohort study of 1-years duration (1998). After weaning from mechanical ventilation and extubation, haemodynamic variables and a 4-point verbal rating pain scale were asseseed at base-line and 60 min after the administration of a single doses of metamizol, ketorolac or propacetamol. The Student's t-test for paired samples was used to compare changes produced by the study medications. A significant, but small, decrease in radial artery blood pressure was observed in all treatment groups which had little clinical relevance; no vasodilator effects were observed and ventricular function showed only minor changes: propacetamol decreased cardiac index by 10% and a 15% decrease in right ventricular work was also observed. Metamizol and ketorolac produced a 10% decrease in the left ventricular work index. Pain scores showed a statistically significant decrease in all treatment groups. The analgesic effects of metamizol, ketorolac and propacetamol were not associated with a clinically significant impairment in haemodynamic function when administered to haemodynamically stable patients.

Comparative safety evaluation of non-narcotic analgesics

Both spontaneous reports and single outcome studies may distort the overall safety evaluation of drugs. We identified epidemiologic studies, published from January 1970 to December 1995, that investigated the association of serious adverse effects with aspirin, diclofenac, acetaminophen, and dipyrone to determine and compare the excess mortality associated with short-term drug use. The estimated excess mortality due to community-acquired agranulocytosis, aplastic anemia, anaphylaxis, and serious upper gastrointestinal complications was 185 per 100 million for aspirin, 592 per 100 million for diclofenac, 20 per 100 million for acetaminophen, and 25 per 100 million for dipyrone. The estimates were largely influenced by the excess mortality associated with upper gastrointestinal complications. A relative risk estimate of 300 or more for the association of dipyrone with agranulocytosis would have been necessary for the excess mortality of dipyrone to be comparable to that of aspirin or diclofenac. Based on published epidemiologic evidence used to determine the excess mortality associated with short-term use of these four non-narcotic analgesics, the current regulatory ranking of the drugs appears inappropriate.

The efficacy of calcium gluconate in ocular hydrofluoric acid burns

1. Although calcium gluconate (CG) is recommended in the treatment of hydrofluoric acid (HF) eye burn its efficacy seems to be controversial, and controlled human or animal studies are limited. The study's objective is to compare the efficacy of 1% CG and normal saline irrigation for the treatment of HF eye injury in animals. 2. 0.05 ml 2% HF was instilled to anesthetized rabbit's eyes. One minute later, four treatment groups were studies: (1) irrigation with normal saline followed by topical antibiotics, corticosteroids and cycloplegics for 48 h (n = 10); (2) irrigation with 1% CG followed by the same topical treatment (n = 9); (3) as group 1 and 1% CG drops over 48 h (n = 10); (4) as group 3, and injection of 1% CG subconjunctivally after irrigation (n = 9). 3. Corneal erosion area, corneal haziness, conjunctival status, vascularization (pannus) and acidity were assessed before injury, immediately after initial treatment and 1, 2, 7 and 14 days thereafter by slit lamp aided by fluorescein staining. 4. Conjunctival pH dropped from 6.0-6.5 to 2.5-3 after injury and increased to 6-6.5 after irrigation. Corneal erosion: smaller in groups 2, 3, significantly so at 2 days, but not different at 14 days. Corneal haziness: more severe in group 4, at 14 days, insignificant. Conjunctival damage: significantly worse in group 4 at 2, 7 and 14 days. Pannus appeared in 2-4 eyes in each group. 5. It seems that for HF injury 1% CG did not have any significant advantage over saline irrigation and topical treatment only. It might have some initial and temporary effect on healing process especially that involving erosion. Given subconjunctivally, 1% CG may be toxic and worsens clinical outcome.

Comparison of the onset and duration of the analgesic effect of dipyrone, 1 or 2 g, by the intramuscular or intravenous route, in acute renal colic

In a double-blind, double-dummy randomized controlled clinical trial, the onset and duration of the analgesic effect of dipyrone, 1 or 2 g, and diclofenac sodium, 75 mg, by either the i.m. or the i.v. route were compared in 293 patients (aged 18-70 years) with acute renal colic. A level of > or = 50 mm on the 100-mm visual analogue scale was required for inclusion in the study. Patients were randomly allocated to six treatment groups, receiving dipyrone 1 g i.m., dipyrone 1 g i.v., dipyrone 2 g i.m.;, dipyrone 2 g i.v., diclofenac sodium 75 mg i.m.; and diclofenac sodium 75 mg i.v., respectively. Evaluations were performed at 10, 20, 30, and 60 min and 2, 4, and 6 h after treatment (time 0). Primary efficacy end points included course of pain, total pain, percentage of patients with a pain improvement of 50% or more at each evaluation time, pain intensity evaluated by the investigator on a 0-3 scale, and differences in pain intensity. The analgesic response was more marked and prolonged among patients receiving dipyrone 2 g i.m. or dipyrone 2 g i.v. There were no significant differences between dipyrone 1 g and diclofenac sodium 75 mg, by either the i.m. or the i.v. route. All treatment regimens were well tolerated.

Double-blind study with dipyrone versus tramadol and butylscopolamine in acute renal colic pain

To investigate the combined analgesic and spasmolytic effect of dipyrone, 104 patients suffering from "severe" or "excruciating" colic pain due to a confirmed calculus in the upper urinary tract were randomized to receive i.v. either 2.5 g dipyrone (36 patients), 100 mg tramadol (35 patients), or 20 mg butylscopolamine (33 patients) in a multicentre, observer-blind, parallel-group study conducted in 8 German centres. The three treatment groups were homogeneous when analyzed by age, sex, height, and baseline pain intensity. Dipyrone was significantly more effective than tramadol in reducing pain for the primary endpoint, pain intensity differences (PID) at 20, 30, and 50 min after drug administration, and was significantly more effective than butylscopolamine at 30 and 50 min for the secondary efficacy endpoint, pain intensity differences on a categorical scale. Dipyrone had the highest SPID0-2 h of the three drugs (P < 0.05). Only 5 patients receiving dipyrone needed "rescue" medication as compared with 13 patients given tramadol and 11 patients receiving butylscopolamine. Adverse events were observed in 4 patients receiving butylscopolamine and in 1 patient each given dipyrone and tramadol. "Distinct" pain relief as assessed on a visual analogue scale (VAS) is a reliable method of determining the onset of analgesic action in the colic pain model.

Formation and excretion of dipyrone metabolites in man

The formation and urinary excretion of the dipyrone metabolites, methylaminoantipyrine (MAA), aminoantipyrine (AA), formylaminoantipyrine (FAA) and acetylaminoantipyrine (AAA) were determined following administration of a single oral 1.0 g dose of dipyrone to 12 healthy volunteers. The AAA/AA plasma ratio showed that 3 subjects were slow and 9 were rapid acetylators. Pharmacokinetic parameters were determined separately for each group. A good correlation was found between the plasma and urine AAA/AA ratios. The renal clearance of the four metabolites was similar for both phenotypes. A significant difference in the rate of formation of dipyrone metabolites was found for AA, 0.25 (slow) vs 0.1 ml.min-1.kg-1 (rapid), and for AAA 0.75 (slow) vs 7.53 ml.min-1.kg-1 (rapid). There were comparable differences between slow and rapid acetylators in the AUC and the urinary excretion extrapolated to infinity for AA and AAA. The present results show that the kinetics of dipyrone metabolites in plasma and urine can provide a useful measure of the activity of the enzymes involved in their production.