Dipyrone elicits substantial inhibition of peripheral cyclooxygenases in humans: new insights into the pharmacology of an old analgesic

NSAIDs, analgesics, antiplatelet drugs, and decline in renal function: a retrospective case-control study with SIDIAP database

INTRODUCTION

We aim to explore the association between NSAIDs consumption, Symptomatic Slow Action Drugs for Osteoarthritis (SYSADOA), analgesics, and antiplatelet drugs, and decline in renal function by estimated Glomerular Filtration Rate (eGFR).

METHODS

We performed a case-control study using the SIDIAP database in Catalonia. We considered defined cases, patients with an eGFR value ≤ 45 ml/min/1.73 m2 in the period 2010-2015 with a previous eGFR value ≥ 60, and no eGFR ≥ 60 after this period. Controls had an eGFR ≥ 60 with no previous eGFR < 60. Five controls were selected for each case, matched by sex, age, index date, Diabetes Mellitus and Hypertension. We estimated Odds Ratios (OR, 95% Confidence Intervals) of decline in renal function for drugs group adjusting with logistic regression models, by consumption measured in DDD. There were n = 18,905 cases and n = 94,456 controls. The mean age was 77 years, 59% were women. The multivariate adjusted model showed a low risk for eGFR decline for NSAIDs (0.92;0.88-0.97), SYSADOA (0.87;0.83-0.91) and acetaminophen (0.84;0.79-0.89), and an high risk for metamizole (1.07;1.03-1.12), and antiplatelet drugs (1.07;1.03-1.11). The low risk in NSAIDs was limited to propionic acid derivatives (0.92;0.88-0.96), whereas an high risk was observed for high doses in both acetic acid derivatives (1.09;1.03-1.15) and Coxibs (1.19;1.08-1.30). Medium and high use of major opioids shows a high risk (1.15;1.03-1.29). Triflusal showed high risk at medium (1.23;1.02-1.48) and high use (1.68;1.40-2.01).

CONCLUSION

We observed a decline in renal function associated with metamizole and antiplatelet agent, especially triflusal, and with high use of acetic acid derivates, Coxibs, and major opioids. Further studies are necessary to confirm these results.

Metamizole in the Management of Musculoskeletal Disorders: Current Concept Review

Metamizole, or dipyrone, has been used for decades as a non-narcotic analgesic, providing pain relief from musculoskeletal disorders and antipyretic and antispasmolytic properties. Despite being in use since the 1920s, its mechanism of action still needs to be discovered. Despite causing fewer adverse effects when compared to other analgesics, its harmful effects on the blood and lack of evidence regarding its teratogenicity make the usage of the drug questionable, which has led to it being removed from the drug market of various countries. This narrative review aims to provide a detailed insight into the mechanism of action and efficacy, comparing its effectiveness and safety with other classes of drugs and the safety profile of metamizole.

In-situ gel injection of poloxamer-based metamizole provides long-acting antipyretic effects

Metamizole easily decomposes in the body and has a short action time and low bioavailability. Hence, frequent injection administrations are needed to maintain its plasma concentration. This study aimed to design and develop an in-situ gel based on poloxamer 407 and 188 to assess its long-acting antipyretic effects. The in-situ gel-forming systep00m with optimum sol-gel transition temperature of 35.9 °C to 36.3 °C could be formed using a combination of P407 at a ratio of 21-23% (w/v) and P188 at a ratio of 2-4% (w/v). In vitro erosion test showed that the in-situ gel's erosion curve and the metamizole release rate both reached about 90% at 6 h, revealing a good linear relationship between the in-situ gel erosion and the drug release. In vitro release test with dialysis tube showed that the release of metamizole from the in-situ gel was remarkably slower than that from the metamizole solution. Approximately 85% of metamizole was released in the dialysis tube within 7 h, implying a good sustained release effect. Pharmacodynamic study showed that the in-situ gel injection extended the action time of metamizole relative to that when using the metamizole solution. Pharmacokinetic study revealed that the in-situ gel significantly increased the blood serum half-life and area under the curve), contributing to a sustained release and improved bioavailability. This study demonstrated that in-situ gel injection could prolong the action of metamizole in the body to reduce the number of administration times and has good clinical application.

The Multifaceted Effects of Non-Steroidal and Non-Opioid Anti-Inflammatory and Analgesic Drugs on Platelets: Current Knowledge, Limitations, and Future Perspectives

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely utilized pharmaceuticals worldwide. Besides their recognized anti-inflammatory effects, these drugs exhibit various other pleiotropic effects in several cells, including platelets. Within this article, the multifaceted properties of NSAIDs on platelet functions, activation and viability, as well as their interaction(s) with established antiplatelet medications, by hindering several platelet agonists' pathways and receptors, are thoroughly reviewed. The efficacy and safety of NSAIDs as adjunctive therapies for conditions involving inflammation and platelet activation are also discussed. Emphasis is given to the antiplatelet potential of commonly administered NSAIDs medications, such as ibuprofen, diclofenac, naproxen and ketoprofen, alongside non-opioid analgesic and antipyretic medications like paracetamol. This article delves into their mechanisms of action against different pathways of platelet activation, aggregation and overall platelet functions, highlighting additional health-promoting properties of these anti-inflammatory and analgesic agents, without neglecting the induced by these drugs' side-effects on platelets' functionality and thrombocytopenia. Environmental issues emerging from the ever-increased subscription of these drugs are also discussed, along with the need for novel water treatment methodologies for their appropriate elimination from water and wastewater samples. Despite being efficiently eliminated during wastewater treatment processes on occasion, NSAIDs remain prevalent and are found at significant concentrations in water bodies that receive effluents from wastewater treatment plants (WWTPs), since there is no one-size-fits-all solution for removing all contaminants from wastewater, depending on the specific characteristics of the wastewater. Several novel methods have been studied, with adsorption being proposed as a cost-effective and environmentally friendly method for wastewater purification from such drugs. This article also presents limitations and future prospects regarding the observed antiplatelet effects of NSAIDs, as well as the potential of novel derivatives of these compounds, with benefits in other important platelet functions.

Pharmacotherapeutic monitoring of dipyrone in northeastern Brazilian donkeys (Equus asinus)

This study aimed to monitor the effects of dipyrone following multiple administrations in northeastern donkeys. Ten castrated male donkeys, aged 6.4 ± 3 years and weighing 130.6 ± 9.8 kg, were administered dipyrone (25 mg/kg IV) every 12 h, resulting in six administrations (D1 to D6) per animal. Blood samples were collected over a 72 h monitoring period. A validated UHPLC-MS/MS method was employed to determine the plasma concentrations of the 4- methylaminoantipyrine (4-MAA) and 4-aminoantipyrine (4-AA). The calculated pharmacokinetic variables of 4-MAA after D1 and D6 were, respectively: Cmax (μg/mL) = 163.60 ± 179.72 and 178.79 ± 196.94; T1/2beta (h) = 2.65 ± 0.65 and 3.37 ± 1.03; and AUC0-t (μg/mL × h) = 240.38 ± 130.87 and 373.52 ± 78.85. The same variables for 4-AA were: Cmax, (μg/mL) = 0.44 ± 0.27 and 0.90 ± 0.31, T1/2beta (h) = 14.77 ± 13.13 and 35.97 and AUC0-t (μg/mL × h) = 3.20 ± 0.43 and 27.73 ± 11.99. Concentrations of 4-MAA exceeded the minimum concentration required for 50% inhibition of cyclooxygenases 1 and 2. However, an accumulation of 4-AA, was observed. Further clinical studies are necessary to ascertain the implications of these findings on the pharmacodynamic response to dipyrone in northeastern donkeys.

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.

Exploring Three Avenues: Chemo- and Regioselective Transformations of 1,2,4-Triketone Analogs into Pyrazoles and Pyridazinones

A convenient approach to substituted pyrazoles and pyridazinones based on 1,2,4-triketones is presented. Chemo- and regiocontrol in condensations of t-Bu, Ph-, 2-thienyl-, and CO2Et-substituted 1,2,4-triketone analogs with hydrazines are described. The direction of preferential nucleophilic attack was shown to be switched depending on the substituent nature in triketone as well as the reaction conditions. The acid and temperature effects on the selectivity of condensations were revealed. Regiochemistry of heterocyclic core formation was confirmed by NMR and XRD studies. The facile construction of heterocyclic motifs bearing acetyl and (or) carbethoxy groups suggests them as promising mono- or bifunctional building blocks for subsequent transformations.

Additive or synergistic analgesic effect of metamizole on standard pain treatment at home after arthroscopic shoulder surgery: A randomised controlled superiority trial

BACKGROUND

There is growing evidence that the analgesic effect of metamizole is mediated at least partly by central mechanisms, including the endocannabinoid/endovanilloid system. Consequently, metamizole may have additive or even synergistic analgesic effects with paracetamol and nonsteroidal anti-inflammatory drugs (NSAID).

OBJECTIVE

This study aimed to assess if triple therapy with metamizole, ibuprofen and paracetamol (MIP) is superior to double therapy with ibuprofen and paracetamol (i.p.) in treating pain at home after ambulatory arthroscopic shoulder surgery.

DESIGN/SETTING/PATIENTS/INTERVENTION

In this double-blind, controlled, high-volume single centre, superiority trial, 110 patients undergoing elective ambulatory arthroscopic shoulder surgery were randomised to receive either MIP ( n  = 55) or i.p. ( n  = 55) orally for 4 days between December 2019 and November 2021. Pain intensity at movement and rest, using a numeric rating scale (NRS), perceived pain relief, use of rescue medication and adverse effects of study medication were recorded at the post-anaesthesia care unit (PACU) and on postoperative day (POD) 1 to 4 and 7. Quality of Recovery (QoR) and satisfaction with study medication were measured at POD 7 with telephone follow-up.

MAIN OUTCOME MEASURE

The primary outcome measure was postoperative pain intensity on movement measured by an 11-point NRS (where 0 = no pain and 10 = worst pain imaginable) on POD 1.

RESULTS

For the primary outcome, superiority of MIP in reducing postoperative pain at movement on POD 1 was not confirmed: mean difference NRS [95% confidence interval (CI), -0.08 (-1.00 to 0.84)]. For pain on movement and at rest, no significant differences were found between groups in the PACU nor on POD 1 to 4 or day 7. Nausea was reported significantly more frequently in the metamizole group (22.6 vs. 58.5; P  < 0.001). Other adverse effects of study medication, rescue opioid consumption, perceived pain relief, QoR at POD 7, and overall patient satisfaction were similar in both groups.

CONCLUSION

Clinically, triple oral treatment with metamizole, paracetamol and ibuprofen is not superior to oral paracetamol and ibuprofen in multimodal pain treatment at home after ambulatory arthroscopic shoulder surgery.

TRIAL REGISTRATION

European Union Clinical Trials Register 2019-002801-23 and Clinicaltrials.gov NCT04082728.

Pharmacokinetic profiles of the two major active metabolites of metamizole, 4-methylaminoantipyrine (MAA) and 4-aminoantipyrine (AA), after intravenous injection in cats

This study aimed to determine the pharmacokinetic profile of two active metabolites of metamizole (dipyrone), N-methyl-4-aminoanthypyrine (MAA) and 4-aminoanthypyrine (AA), after intravenous administration in cats. Eight healthy mixed-breed cats were intravenously administered metamizole (25 mg/kg). Blood samples were collected at predetermined time points for up to 48 h after administration. Information on behavioral changes in the animals and adverse effects was collected. Plasma aliquots were processed and analyzed using the ultra-performance liquid chromatography tandem mass spectrometry technique. A validated UPLC-MS/MS method was used to characterize the pharmacokinetics of MAA and AA. Salivation was identified as an adverse clinical sign. The mean maximal plasma concentrations of MAA and AA were 29.31 ± 24.57 μg/mL and 1.69 ± 0.36 μg/mL, with half-lives of around 4.98 and 14 h, respectively. The area under the plasma concentration curve values were 28.54 ± 11.33 and 49.54 ± 11.38 h*μg/mL for MAA and AA, respectively. The plasma concentration of MAA was detectable for up to 24 h and was smaller than AA. AA was detectable for >48 h. Results suggest that metamizole is converted into active metabolites in cats. Further PK/PD and safety studies should be performed before defining the dose or administration intervals for clinical use.

2-Arylpropionic Acid Pyrazolamides as Cannabinoid CB2 Receptor Inverse Agonists Endowed with Anti-Inflammatory Properties

Among the most recent proposals regarding the mechanism of action of dipyrone, the modulation of cannabinoid receptors CB₁ and CB₂ appears to be a promising hypothesis. In this context, the present work describes a series of five novel pyrazolamides (7-11) designed as molecular hybrids of dipyrone metabolites and NSAIDs, such as ibuprofen and flurbiprofen. Target compounds were obtained in good overall yields (50-80%) by classical amide coupling between 4-aminoantipyrine and arylacetic or arylpropionic acids, followed in some cases by N-methylation of the amide group. The compounds presented good physicochemical properties in addition to stability to chemical (pH 2 and 7.4) and enzymatic (plasma esterases) hydrolysis and showed medium to high gastrointestinal and BBB permeabilities in the PAMPA assay. When subjected to functional testing on CB₁- or CB₂-transfected cells, compounds demonstrated an inverse agonist profile on CB₂ receptors and the further characterization of compound LASSBio-2265 (11) revealed moderate binding affinity to CB₂ receptor (K_i = 16 µM) with an EC₅₀ = 0.36 µM (E_max = 63%). LASSBio-2265 (11) (at 1, 3, and 10 mg/kg p.o.) was investigated in the formalin test in mice and a remarkable analgesic activity in the late inflammatory phase was observed, suggesting it could be promising for the treatment of pain syndromes associated with chronic inflammatory diseases.

Impact of analgesic regimen on patient outcome following subarachnoid hemorrhage: positive adjuvant effects of metamizole

INTRODUCTION

Various analgesics are used to control intense headaches in patients following subarachnoid hemorrhage. In addition to pain control, it has been shown that some analgesics can affect various pathophysiological cascades. Therefore, we devised a study to assess whether the use of metamizole has a significant impact on the development of ischemic complications, hydrocephalus, and the overall outcome in patients following aneurysmal subarachnoid hemorrhage in the context of the other non-opioids and opioids effects.

METHODS

In our retrospective, single-center cohort study, we enrolled 192 patients diagnosed with subarachnoid hemorrhage. We recorded their initial clinical status, comorbidities, and the daily dosage of analgesics over 14 days of hospitalization after the onset of subarachnoid hemorrhage. Using univariate and subsequent multivariate logistic regression analysis, we assessed the influence of various factors, including analgesics, on the development of delayed cerebral ischemia and hydrocephalus, as well as on 2-week and 6-month outcomes.

RESULTS

Although the administration of non-opioids, in general, had no effect on the development of delayed cerebral ischemia or hydrocephalus, the use of metamizole as the main analgesic was associated with a significantly lower chance of poor outcome at both 2-weeks and 6-months, as well as the development of delayed cerebral ischemia. As opioids were indicated primarily for analgosedation in mechanically ventilated patients with poor clinical status, their usage was associated with a significantly higher chance of poor outcome, delayed cerebral ischemia, and hydrocephalus.

CONCLUSION

Our results suggest that the prescription of metamizole may be associated with better outcomes and a lower chance of delayed cerebral ischemia development in patients after subarachnoid hemorrhage. Considering the retrospective nature of our study and the limited worldwide availability of metamizole due to its prohibition in some countries, our results do not demonstrate a clear benefit but rather justify the need for subsequent prospective studies.

Pain Management and Analgesics Used in Small Mammals during Post-Operative Period with an Emphasis on Metamizole (Dipyrone) as an Alternative Medication

Metamizole (dipyrone) is a widely used non-opioid analgesic in both human and animal medicine. Metamizole's safety has been the topic of numerous opposing debates, given the fact that in certain countries metamizole is frequently used as an over-the-counter (OTC) medicine, while in others it is banned due to the risk of agranulocytosis. Further, small mammals such as rabbits, ferrets, rodents, and hedgehogs have become some of the most common pets present in veterinary practice, and each of these species has specific analgesic needs due to their anatomy and physiology. The key to providing appropriate medical care is in finding a substance that has minimal negative effects. In small mammals, analgesia is an important factor and, it happens frequently that, pain in these patients is not well managed. Post-operative pain management is an important topic in the welfare of animals. The objectives of this review, thus, were to provide a concise overview of analgesics that are used in the treatment of postoperative pain in small mammals (e.g., rabbits and rodents) and to highlight the importance of this product, metamizole, in veterinary medicine, as well as the potential of this substance as an alternative analgesic for the treatment of postoperative pain in small mammals.

Metamizole-Associated Risks in Decompensated Hepatic Cirrhosis

BACKGROUND

Because of the increased risk of acute renal failure (ARF), the use of cyclooxygenase (COX) inhibitors is not recommended in patients with decompensated hepatic cirrhosis. Metamizole is not a classic COX inhibitor, but there are insufficient data to support its safe use. In this study, we investigate the effect of metamizole on the risk of ARF in these patients.

METHODS

Metamizole use, ARF incidence, and patient mortality were examined in a large, retrospective, exploratory cohort and validated with data from a prospective registry.

RESULTS

523 patients were evaluated in the exploratory cohort. Metamizole use at baseline was documented in 110 cases (21%) and was independently associated with the development of ARF, severe (grade 3) ARF, and lower survival without liver transplantation at follow-up on day 28 (HR: 2.2, p < 0.001; HR: 2.8, p < 0.001; and HR: 2.6, p < 0.001, respectively). Interestingly, the risk of ARF depended on the dose of metamizole administered (HR: 1.038, p < 0.001). Compared to patients who were treated with opioids, the rate of ARF was higher in the metamizole group (49% vs. 79%, p = 0.014). An increased risk of ARF with metamizole use was also demonstrated in the independent validation cohort (p < 0.001).

CONCLUSION

Metamizole therapy, especially at high doses, should only be used with a high level of caution in patients with decompensated cirrhosis.

Mastocytosis presenting with mast cell‐mediator release‐associated symptoms elicited by cyclo oxygenase inhibitors: prevalence, clinical, and laboratory features

Background

Nonsteroidal anti‐inflammatory drugs (NSAIDs) are frequently avoided in mastocytosis, because of a potential increased risk for drug hypersensitivity reactions (DHRs) due to inhibition of cyclo‐oxygenase (COX), subsequent depletion of prostaglandin E₂ and release of leukotrienes.

Objectives

Here, we aimed at determining the prevalence of mast cell (MC) mediator release symptoms triggered by NSAIDs in mastocytosis patients and the associated clinical and laboratory features of the disease.

Methods

Medical records from 418 adults to 223 pediatric mastocytosis patients were retrospectively reviewed. Patients were classified according to tolerance patterns to NSAIDs and other COX inhibitors (COXi) and compared for epidemiological, clinical and laboratory findings.

Results

Overall, 87% of adults and 91% of pediatric patients tolerated NSAIDs and other COXi. Among adult and pediatric patients presenting DHRs, 5% and 0% reacted to multiple NSAIDs, 4% and 0.7% were single reactors, and 3% and 8% were single reactors with known tolerance to paracetamol but unknown tolerance to other COXi, respectively. Among adults, hypersensitivity to ≥2 drugs was more frequent among females (p = 0.009), patients with prior history of anaphylaxis to triggers other than NSAIDs or other COXi and Hymenoptera venom (p = 0.009), presence of baseline flushing (p = 0.02), baseline serum tryptase ≥48 ng/ml (p = 0.005) and multilineage KIT mutation (p = 0.02). In contrast, tolerance to NSAIDs and other COXi was more frequent among males (p = 0.02), in patients with anaphylaxis caused by Hymenoptera venom (p = 0.02), among individuals who had skin lesions due to mastocytosis (p = 0.01), and in cases that had no baseline pruritus (p = 0.006). Based on these parameters, a score model was designed to stratify mastocytosis patients who have never received NSAIDs or other COXi apart from paracetamol, according to their risk of DHR.

Conclusions

Our results suggest that despite the frequency of MC mediator related symptoms elicited by NSAIDs and other COXi apart from paracetamol is increased among mastocytosis patients versus the general population, it is lower than previously estimated and associated with unique disease features. Patients that tolerated NSAIDs and other COXi following disease onset should keep using them. In turn, adults with unknown tolerance to such drugs and a positive score should be challenged with a preferential/selective COX‐2 inhibitor, while the remaining may be challenged with ibuprofen.

Pharmacokinetics of metamizole (dipyrone) as an add-on in calves undergoing umbilical surgery

This preliminary clinical investigation of the pharmacokinetic behavior of the main metamizole (dipyrone) metabolites 4-methylaminoantipyrine (4-MAA) and 4-aminoantipyrine (4-AA) in calves undergoing umbilical surgery is part of an already published main study. A single intravenous dose of metamizole was added to ketamine/xylazine/isoflurane anesthesia. Eight Simmental calves weighing 90 ± 10.8 kg and aged 47.6 ± 10.4 days received 40 mg/kg metamizole intravenously 10 minutes prior to general anesthesia. Blood samples were collected over 24 hours and analyzed for 4-MAA and 4-AA. Meloxicam was additionally given twice: 2.5 hours pre- and 20.5 hours postsurgically. The pharmacokinetic profile of 4-MAA was best fitted to a two-compartment model and was characterized by a fast distribution half-life and slow elimination half-life (t_½alpha = 5.29 minutes, t_½beta = 9.49 hours). The maximum concentration (C_max 101.63 μg/mL) was detected at the first measurement time point 15 minutes after administration. In contrast, 4-AA showed fast, high and biphasic plasma peak concentration behavior in five calves (2.54–2.66 μg/mL after 15–30 minutes, and 2.10–2.14 μg/mL after 2–3.5 hours) with a t_½beta of 8.87 hours, indicating a rapid distribution and subsequent redistribution from well-perfused organs. Alternatively, three calves exhibited a slower and lower monophasic plasma peak concentration (1.66 μg/mL after 6.5 hours) with a t_½beta of 6.23 hours, indicating slow accumulation in the intravascular compartment. The maximum concentration and area under the plasma concentration curve (AUC) of 4-AA were lower than those of 4-MAA. This metabolic behavior supports our already published data on clinical monitoring and plasma cortisol concentrations (PCCs). Compared to those of saline controls, lower PCCs correspond to the t_½alpha of 4-MAA. Data on T_max and t_½beta also match these clinical observations. However, further studies are required to assess the exact analgesic mechanism and potency of the metamizole metabolites in calves.

The hyperthermic effect of central cholecystokinin is mediated by the cyclooxygenase-2 pathway

Cholecystokinin (CCK) increases core body temperature via CCK₂ receptors when administered intracerebroventricularly (icv). The mechanisms of CCK-induced hyperthermia are unknown, and it is also unknown whether CCK contributes to the fever response to systemic inflammation. We studied the interaction between central CCK signaling and the cyclooxygenase (COX) pathway. Body temperature was measured in adult male Wistar rats pretreated with intraperitoneal infusion of the nonselective COX enzyme inhibitor metamizol (120 mg/kg) or a selective COX-2 inhibitor, meloxicam, or etoricoxib (10 mg/kg for both) and, 30 min later, treated with intracerebroventricular CCK (1.7 µg/kg). In separate experiments, CCK-induced neuronal activation (with and without COX inhibition) was studied in thermoregulation- and feeding-related nuclei with c-Fos immunohistochemistry. CCK increased body temperature by ∼0.4°C from 10 min postinfusion, which was attenuated by metamizol. CCK reduced the number of c-Fos-positive cells in the median preoptic area (by ∼70%) but increased it in the dorsal hypothalamic area and in the rostral raphe pallidus (by ∼50% in both); all these changes were completely blocked with metamizol. In contrast, CCK-induced satiety and neuronal activation in the ventromedial hypothalamus were not influenced by metamizol. CCK-induced hyperthermia was also completely blocked with both selective COX-2 inhibitors studied. Finally, the CCK₂ receptor antagonist YM022 (10 µg/kg icv) attenuated the late phases of fever induced by bacterial lipopolysaccharide (10 µg/kg; intravenously). We conclude that centrally administered CCK causes hyperthermia through changes in the activity of "classical" thermoeffector pathways and that the activation of COX-2 is required for the development of this response.NEW & NOTEWORTHY An association between central cholecystokinin signaling and the cyclooxygenase-prostaglandin E pathway has been proposed but remained poorly understood. We show that the hyperthermic response to the central administration of cholecystokinin alters the neuronal activity within efferent thermoeffector pathways and that these effects are fully blocked by the inhibition of cyclooxygenase. We also show that the activation of cyclooxygenase-2 is required for the hyperthermic effect of cholecystokinin and that cholecystokinin is a modulator of endotoxin-induced fever.

Pharmacokinetics of dipyrone in horses: A multi-dose, dose escalation study

Dipyrone is a non-opioid, nonsteroidal anti-inflammatory drug with antipyretic and analgesic properties commonly used in horses. Dipyrone is rapidly hydrolyzed to the primary active metabolite 4-methylaminoantipyrine (4-MAA). The purpose of this study was to determine the pharmacokinetic profile of 4-MAA following repeated and escalating doses of intravenously administered dipyrone. Twenty-six horses were randomly allocated to five treatment groups (one placebo group and four dipyrone groups [30 mg/kg q8h, 30 mg/kg q12h, 60 mg/kg q8h, and 90 mg/kg q12h]) and treated for nine consecutive days. Blood was collected at predetermined timepoints, and plasma was analyzed for 4-MAA concentrations with a validated LC/MS/MS method. Following a single dose, there was a linear correlation to the maximum concentration (Cmax ) achieved. There was a disproportionate increase in the minimum concentration (Cmin ) of 4-MAA with accumulation occurring at higher doses or more frequent dosing intervals. Significant differences were noted in 4-MAA Cmax , half-life, and area under the curve during the dosing interval (AUCtau ) when dipyrone was administered at 30 mg/kg q12h versus q8h. Adverse effects attributed to drug administration were not noted.

Comparative Effects of Metamizole (Dipyrone) and Naproxen on Renal Function and Prostacyclin Synthesis in Salt-Depleted Healthy Subjects - A Randomized Controlled Parallel Group Study

Aim: The objective was to investigate the effect of metamizole on renal function in healthy, salt-depleted volunteers. In addition, the pharmacokinetics of the four major metamizole metabolites were assessed and correlated with the pharmacodynamic effect using urinary excretion of the prostacyclin metabolite 6-keto-prostaglandin F1α. Methods: Fifteen healthy male volunteers were studied in an open-label randomized controlled parallel group study. Eight subjects received oral metamizole 1,000 mg three times daily and seven subjects naproxen 500 mg twice daily for 7 days. All subjects were on a low sodium diet (50 mmol sodium/day) starting 1 week prior to dosing until the end of the study. Glomerular filtration rate was measured using inulin clearance. Urinary excretion of sodium, potassium, creatinine, 6-keto-prostaglandin F1α, and pharmacokinetic parameters of naproxen and metamizole metabolites were assessed after the first and after repeated dosing. Results: In moderately sodium-depleted healthy subjects, single or multiple dose metamizole or naproxen did not significantly affect inulin and creatinine clearance or sodium excretion. Both drugs reduced renal 6-keto-prostaglandin F1α excretion after single and repeated dosing. The effect started 2 h after intake, persisted for the entire dosing period and correlated with the concentration-profile of naproxen and the active metamizole metabolite 4-methylaminoantipyrine (4-MAA). PKPD modelling indicated less potent COX-inhibition by 4-MAA (EC₅₀ 0.69 ± 0.27 µM) compared with naproxen (EC₅₀ 0.034 ± 0.033 µM). Conclusions: Short term treatment with metamizole or naproxen has no significant effect on renal function in moderately sodium depleted healthy subjects. At clinically relevant doses, 4-MAA and naproxen both inhibit COX-mediated renal prostacyclin synthesis.

Diastereoselective synthesis of indolenine-based spiro[pyrazolone-4,2'-pyrrolidine] scaffolds via 1,3-dipolar cycloaddition of 4-aminopyrazolones, aldehydes, and indolenines

In this work, we report a one-pot [3 + 2] cycloaddition of 4-aminopyrazolones, indolenines, and aldehydes. The reaction utilized in situ generated azomethine ylides as 1,3-dipoles and 2-alkenylindolenines as dipolarophiles affording indolenine-derived spiro[pyrazolone-4,2'-pyrrolidine] scaffolds with four contiguous stereocenters with excellent yields (up to 95%) and diastereoselectivities (up to >20 : 1 dr) under simple conditions. The in situ generation of azomethine ylides and dipolarophiles in one pot is a unique feature of this process.

[Perioperative analgesia with nonopioid analgesics : Joint interdisciplinary consensus-based recommendations of the German Pain Society, the German Society of Anaesthesiology and Intensive Care Medicine and the German Society of Surgery]

BACKGROUND

Nonopioid analgesics are frequently used for perioperative analgesia; however, insufficient research is available on several practical issues. Often hospitals have no strategy for how to proceed, e.g., for informing patients or for the timing of perioperative administration of nonopioid analgesics.

METHODS

An expert panel representing the German national societies of pain, anaesthesiology and intensive care medicine and surgery developed recommendations for the perioperative use of nonopioid analgesics within a formal, structured consensus process.

RESULTS

The panel agreed that nonopioid analgesics shall be part of a multimodal analgesia concept and that patients have to be informed preoperatively about possible complications and alternative treatment options. Patients' history of pain and analgesic intake shall be evaluated. Patients at risk of severe postoperative pain and possible chronification of postsurgical pain shall be identified. Depending on the duration of surgery, nonopioid analgesics can already be administered preoperatively or intraoperatively so that plasma concentrations are sufficient after emergence from anesthesia. Nonopioid analgesics or combinations of analgesics shall be administered for a limited time only. An interdisciplinary written standard of care, comprising the nonopioid analgesic of choice, possible alternatives, adequate dosing and timing of administration as well as surgery-specific policies, have to be agreed upon by all departments involved. At discharge, the patient's physician shall be informed of analgesics given and those necessary after discharge. Patients shall be informed of possible side effects and symptoms and timely discontinuation of analgesic drugs.

CONCLUSION

The use of nonopioid analgesics as part of a perioperative multimodal concept should be approved and established as an interdisciplinary and interprofessional concept for the adequate treatment of postoperative pain.

[Perioperative analgesia with nonopioid analgesics : Joint interdisciplinary consensus-based recommendations of the German Pain Society, the German Society of Anaesthesiology and Intensive Care Medicine and the German Society of Surgery]

BACKGROUND

Nonopioid analgesics are frequently used for perioperative analgesia; however, insufficient research is available on several practical issues. Often hospitals have no strategy for how to proceed, e.g., for informing patients or for the timing of perioperative administration of nonopioid analgesics.

METHODS

An expert panel representing the German national societies of pain, anaesthesiology and intensive care medicine and surgery developed recommendations for the perioperative use of nonopioid analgesics within a formal, structured consensus process.

RESULTS

The panel agreed that nonopioid analgesics shall be part of a multimodal analgesia concept and that patients have to be informed preoperatively about possible complications and alternative treatment options. Patients' history of pain and analgesic intake shall be evaluated. Patients at risk of severe postoperative pain and possible chronification of postsurgical pain shall be identified. Depending on the duration of surgery, nonopioid analgesics can already be administered preoperatively or intraoperatively so that plasma concentrations are sufficient after emergence from anesthesia. Nonopioid analgesics or combinations of analgesics shall be administered for a limited time only. An interdisciplinary written standard of care, comprising the nonopioid analgesic of choice, possible alternatives, adequate dosing and timing of administration as well as surgery-specific policies, have to be agreed upon by all departments involved. At discharge, the patient's physician shall be informed of analgesics given and those necessary after discharge. Patients shall be informed of possible side effects and symptoms and timely discontinuation of analgesic drugs.

CONCLUSION

The use of nonopioid analgesics as part of a perioperative multimodal concept should be approved and established as an interdisciplinary and interprofessional concept for the adequate treatment of postoperative pain.

Pharmacokinetic properties of metamizole active metabolites in Northeastern Brazilian donkeys (Equus asinus)

Metamizole (MT), also known as dipyrone, is an analgesic and antipyretic drug labeled for use in humans and domestic animals in some countries. As with other drugs, the administration of MT in donkeys is based on studies carried out with horses. In the present report, we aimed to determine the pharmacokinetics of the two main metamizole active metabolites (N-methyl-4-aminoantipyrine [MAA] and 4-aminoantipyrine [AA]) following 10 (M₁₀ ) and 25 mg/kg (M₂₅ ) IV metamizole doses in Northeast Brazilian donkeys (n = 10). Blood was collected at predetermined times within over 48 h; MAA and AA plasma concentrations were determined by a validated LC-MS/MS method. The metabolites were quantifiable in the M₁₀ until 12 h and M₂₅ until 24 h after drug administration. As expected, AUC_0→t , AUC_0→∞, and C_max demonstrated significant differences increases in metamizole metabolites profiles when groups were compared. No adverse effects were observed. This study indicates the need for an extremely sensitive analytical method to adequately characterize the pharmacokinetics of active metabolites of MT, MAA, and AA. In conclusion, the method developed in this research was able to measure the active metabolites of metamizole and with that it was possible to establish their pharmacokinetic profile. Furthermore, after projection of the minimum MAA concentrations, it is possible to infer that the dose of 10 mg/kg will be used on donkeys at 6 h intervals, while the M25 group at 12 h intervals. However, clinical studies are needed to assess this hypothesis.

[Perioperative analgesia with nonopioid analgesics : Joint interdisciplinary consensus-based recommendations of the German Pain Society, the German Society of Anaesthesiology and Intensive Care Medicine and the German Society of Surgery]

Hintergrund

Nichtopioidanalgetika werden bei vielen Patienten zur perioperativen Analgesie eingesetzt. Zu einigen praktischen Fragen beim Einsatz von Nichtopioidanalgetika liegen z. T. nur wenig Informationen aus Studien vor, und in Krankenhäusern existieren häufig keine Konzepte zum Vorgehen, z. B. zur Patientenaufklärung und zum Zeitpunkt der perioperativen Gabe.

Methodik

Eine Expertengruppe der beteiligten Fachgesellschaften hat konsensbasierte Empfehlungen zum perioperativen Einsatz von Nichtopioidanalgetika erarbeitet und in einem strukturierten formalen Konsensusprozess verabschiedet.

Ergebnisse

Die Arbeitsgruppe stimmt überein, dass Nichtopioidanalgetika Bestandteil eines perioperativen multimodalen Analgesiekonzepts sein sollen und Patienten präoperativ über Nutzen, Risiken und alternative Behandlungsmöglichkeiten aufgeklärt werden sollen. Die präoperative Patienteninformation und -edukation soll auch eine Schmerz- und Analgetikaanamnese umfassen und Patienten mit Risikofaktoren für starke Schmerzen und eine Schmerzchronifizierung sollen identifiziert werden. Unter Berücksichtigung von Kontraindikationen können Nichtopioidanalgetika abhängig von der Operationsdauer auch schon prä- oder intraoperativ gegeben werden, um nach Beendigung der Anästhesie ausreichende Plasmakonzentrationen zu erzielen. Nichtopioidanalgetika oder Kombinationen von (Nichtopioid‑)Analgetika sollen nur für einen begrenzten Zeitraum gegeben werden. Ein gemeinsam erarbeiteter abteilungsübergreifender Behandlungsstandard mit dem Nichtopioidanalgetikum erster Wahl, weiteren Therapieoptionen sowie adäquaten Dosierungen, ergänzt durch eingriffsspezifische Konzepte, soll schriftlich hinterlegt werden. Bei Entlassung aus dem Krankenhaus soll der nachbehandelnde Arzt zu perioperativ gegebenen und aktuell noch eingenommenen Analgetika schriftliche Informationen erhalten. Patienten sollen zu möglichen Nebenwirkungen der Analgetika und ihrer Symptome, die auch nach Krankenhausentlassung auftreten können, und die befristete Einnahmedauer informiert werden.

Schlussfolgerung

Die Anwendung von Nichtopioidanalgetika soll als Bestandteil eines perioperativen multimodalen Analgesiekonzepts mit klaren Vorgaben zu Indikationen, Kontraindikationen, Dosierungen und Behandlungsdauer in einem abteilungsübergreifenden Behandlungsstandard schriftlich hinterlegt werden.

Zusatzmaterial online

Die Offenlegung von Interessen ist in der Online-Version dieses Artikels (10.1007/s00104-021-01421-w) enthalten.

A possible increased risk of metamizole-associated neutropenia among COVID-19 patients

Metamizole is commonly used as analgesic and antipyretic drug. The use of metamizole is prohibited in several countries due to its rare side effect of neutropenia and even agranulocytosis. Among the many symptoms of COVID-19, fever and diffuse pain predominant and therefore it can be assumed that metamizole may be widely used in the current epidemic period. So far, there have been no reports on the safety of metamizole in COVID-19 patients. We describe a series of 3 patients who developed severe neutropenia under metamizole treatment, raising a concern of a possible increased risk of this side effect among COVID-19 patients.

Cyclooxygenases 1 and 2 inhibition and analgesic efficacy of dipyrone at different doses or meloxicam in cats after ovariohysterectomy

OBJECTIVE

To evaluate the cyclooxygenases (COX) inhibition, adverse effects and analgesic efficacy of dipyrone or meloxicam in cats undergoing elective ovariohysterectomy.

STUDY DESIGN

Prospective, blinded, randomized, clinical study.

ANIMALS

A total of 30 healthy young cats.

METHODS

The cats were randomly assigned to three postoperative groups: D25 (dipyrone 25 mg kg^-1 every 24 hours), D12.5 (dipyrone 12.5 mg kg^-1 every 12 hours) and M (meloxicam 0.1 mg kg^-1 every 24 hours). In the first 24 hours, the drugs were administered intravenously (IV), and then orally for 6 (dipyrone) or 3 days (meloxicam). Prostanoids thromboxane B₂ and prostaglandin E₂ concentrations served as indicators of COX activity and, with physiological variables and pain and sedation scores, were measured for 24 hours after first analgesic administration. Rescue analgesia (tramadol, 2 mg kg^-1 IV) was provided if Glasgow feline composite measure pain scale (CMPS-Feline) ≥5. Laboratory tests included symmetric dimethylarginine and adverse effects were evaluated regularly up to 7 and 10 days after surgery, respectively. Parametric and nonparametric data were analyzed with two-way anova and Kruskal-Wallis tests, respectively (p < 0.05).

RESULTS

In the first half hour after analgesic administration, COX-1 activity was close to zero and remained significantly lower than before drug administration for 24 hours in all groups. The inhibition of COX-2 activity was significant for 30 minutes in all groups and up to 4 hours in group M. No alterations in laboratory tests or significant adverse effects were observed. Pain scores and need for rescue analgesia did not differ statistically among groups.

CONCLUSIONS

Dipyrone at both doses and meloxicam provided a nonselective inhibition of COX-1 and -2 activities and effective analgesia without causing significant adverse effects or laboratory tests alterations.

CLINICAL RELEVANCE

Dipyrone at both doses provides equally effective analgesia without causing adverse effects in cats undergoing ovariohysterectomy.

[Considerations concerning the perioperative use of metamizole]

BACKGROUND

The non-opioid analgesic metamizole (dipyrone) is approved for the treatment of severe pain and is often used in the perioperative period. As it can cause agranulocytosis, a severe adverse event, its perioperative administration is controversially discussed.

OBJECTIVE

Is there enough evidence for a high risk of metamizol-induced agranulocytosis (MIA)? What are the consequences of its perioperative use with respect to the risk profiles of alternative analgesics?

MATERIAL AND METHODS

Rapid review of the literature on the risk of MIA and adverse effects of non-opioid analgesics.

RESULTS

The incidence of MIA is estimated to be one case per million inhabitants per year. The risk seems low compared to other drugs associated with a risk of agranulocytosis, such as antithyroid drugs and ticlopidine. The risk profile of metamizole concerning hepatotoxicity, nephrotoxicity, bleeding and cardiovascular adverse effects is favorable compared to other non-opioid analgesics. None of the non-opioid analgesics are licensed to be administered intraoperatively.

CONCLUSION

The perioperative use of metamizole is possible after a thorough evaluation of the indications as it provides good analgesia with a generally favorable side effect profile and is administered intravenously. The risk of agranulocytosis is small but needs to be mentioned during patient informed consent in order to optimize early recognition. Intraoperative administration aims at reducing the expected severe postoperative pain. A documentation and justification for the evaluation of the indications are recommended.

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.

Evaluation of postoperative pain and toxicological aspects of the use of dipyrone and tramadol in cats

OBJECTIVES

The aim of this study was to evaluate the effects of dipyrone and tramadol, used for 5 days, on postoperative pain, hematological and biochemical parameters, and oxidative markers on erythrocytes.

METHODS

Twenty-eight healthy cats underwent ovariohysterectomy and were randomly allocated to four groups (each n = 7), according to the postoperative treatment administered intravenously: control (saline 1 ml q8h), DIP1 (dipyrone 25 mg/kg q24h), DIP2 (dipyrone 25 mg/kg q12h) and DIP3 (dipyrone 25 mg/kg q8h). All animals received tramadol (2 mg/kg q8h). Pain was assessed by visual analog (VAS), multidimensional UNESP and Glasgow pain scales for cats preoperatively and at 3, 6, 12, 24, 36 and 48 h after extubation. Venous blood was collected daily for 5 days, and on day 10, to perform a complete blood count (CBC) and determine the percentage of Heinz bodies (HBs). Serum biochemistry was evaluated preoperatively and on days 5 and 10; superoxide dismutase (SOD), catalase (CAT), myeloperoxidase (MPO) and lipoperoxidation were evaluated preoperatively and on days 3, 5 and 10.

RESULTS

Control cats had higher pain scores than DIP3 cats by UNESP (P = 0.0065), and DIP2 (P = 0.0035) and DIP3 cats (P = 0.0108) by VAS 3 h postoperatively. Rescue analgesia was required by two animals in the control group and one each in the DIP1 and DIP2 groups. There was no difference in SOD or CAT among groups. On day 5, MPO was more active in DIP2 than in DIP3 cats (P = 0.0274). No difference in lipoperoxidation among treatment and control cats was found. CBC remained constant and without statistical difference among groups. Control, DIP2 and DIP3 cats presented a similar percentage of HBs on day 10. Biochemical variables were similar among groups and times.

CONCLUSIONS AND RELEVANCE

The administration of dipyrone in cats, when used in combination with tramadol, did not ensure better analgesia than tramadol alone. Dipyrone did not significantly affect biochemical variables and oxidative markers, despite minimal, clinically irrelevant, hematological differences between groups.

Hypersensitivity to dipyrone in aspirin-exacerbated respiratory disease patients is associated with urticaria

OBJECTIVE

To phenotype patients with aspirin-exacerbated respiratory disease (AERD) according to the presence of atopy, urticaria and level of peripheral eosinophils.

METHODS

This study included adult asthmatic patients with AERD followed up at a tertiary hospital. They were classified according to atopy and/or urticaria, assessing clinical and laboratorial differences among the groups in order to identify possible aggravating factors of the disease.

RESULTS

We included 73 patients, 78.1% being female with a mean age of 54.0 years. Severe asthma was observed in 68.5% and respiratory exacerbation with dipyrone in 67.1% of these patients. They had median total serum IgE of 191.6 IU/mL, mean peripheral eosinophils of 718.5 cells/mm³, and 50.7% were atopic. Urticaria was observed in 32.9% of them, and exacerbations were more often triggered by dipyrone (p = .016). Atopic patients were younger than nonatopic patients (p = .023), and had, on average, higher total serum IgE levels (p = .022). We observed a good correlation between asthma severity and peripheral eosinophils count (r² = 026; p = .021).

CONCLUSIONS

In this study, severe asthma was highly prevalent in AERD patients. Likewise, urticaria was quite prevalent and its presence was associated with dipyrone induced hypersensitivity reaction. Atopy was found in half of the patients, with no association with asthma severity. Patients with higher levels of peripheral eosinophils had more severe asthma. Dypirone hypersensitivity may be a marker for concomitant respiratory and cutaneous hypersensitivity reactions.

Nociception in a Progressive Multiple Sclerosis Model in Mice Is Dependent on Spinal TRPA1 Channel Activation

Central neuropathic pain is a common untreated symptom in progressive multiple sclerosis (PMS) and is associated with poor quality of life and interference with patients' daily activities. The neuroinflammation process and mitochondrial dysfunction in the PMS lesions generate reactive species. The transient potential receptor ankyrin 1 (TRPA1) has been identified as one of the major mechanisms that contribute to neuropathic pain signaling and can be activated by reactive compounds. Thus, the goal of our study was to evaluate the role of spinal TRPA1 in the central neuropathic pain observed in a PMS model in mice. We used C57BL/6 female mice (20-30 g), and the PMS model was induced by the experimental autoimmune encephalomyelitis (EAE) using mouse myelin oligodendrocyte glycoprotein (MOG_35-55) antigen and CFA (complete Freund's adjuvant). Mice developed progressive clinical score, with motor impairment observed after 15 days of induction. This model induced mechanical and cold allodynia and heat hyperalgesia which were measured up to 14 days after induction. The hypersensitivity observed was reduced by the administration of selective TRPA1 antagonists (HC-030031 and A-967079, via intrathecal and intragastric), antioxidants (α-lipoic acid and apocynin, via intrathecal and intragastric), and TRPA1 antisense oligonucleotide (via intrathecal). We also observed an increase in TRPA1 mRNA levels, NADPH oxidase activity, and 4-hydroxinonenal (a TRPA1 agonist) levels in spinal cord samples of PMS-EAE induced animals. In conclusion, these results support the hypothesis of the TRPA1 receptor involvement in nociception observed in a PMS-EAE model in mice.

Development and validation of an LC–MS/MS method for the bioanalysis of the major metamizole metabolites in human plasma

Aim: Metamizole is a frequently used antipyretic and analgesic prodrug, yet its pharmacokinetics has not been thoroughly studied in infants and with coadministered medications. Thus, an LC–MS/MS method was developed to quantify the four major metamizole metabolites in human plasma. Methodology: Pre- and postcolumn infusion was installed to enable robust analyte retention and electrospray ionization following deproteinization of plasma samples. Results: The method was linear (R > 0.996), accurate (93.1–106.0%) and precise (≤12.7%). Mean recovery was more than 91.8% and ion suppression less than 13.1% for all analytes. Pharmacokinetic profiles were reproducible after 4 years at -80°C except for the formylated metabolite (-22.2%). Conclusion: The method fulfilled pertinent criteria of validation guidelines and required only little sample volume. The method therefore qualifies for metamizole analyses in children.

[Pharmacology of non-opioid analgesics]

Due to high prescription rates as well as the frequent use as over the counter drugs, it is of interest to consider non-opioid analgesics when evaluating the quality and appropriateness of a given overall medication. This article sums up the basic pharmacology and main adverse effects of these analgesics. Non-opioids can be further classified according to their additional mechanisms of action besides analgesia. High-dose acetylsalicylic acid, traditional nonsteroidal anti-inflammatory drugs, and coxibs exhibit antipyretic and anti-inflammatory properties. Acetaminophen and metamizole (dipyrone) are analgesics and antipyretic agents, while metamizole exhibits also spasmolytic effects. Capsaicin and intrathecal ziconotide are pure analgesics.

Population-based case-control study: chemoprotection of colorectal cancer with non-aspirin nonsteroidal anti-inflammatory drugs and other drugs for pain control

BACKGROUND

Inflammation and overexpression of cyclooxygenase-2 (COX-2) have been described to play a key role in the progression from nonpathologic intestinal mucosa to colorectal cancer (CRC).

AIMS

To assess the chemoprotective effect of non-aspirin nonsteroidal anti-inflammatory drugs (NA-NSAIDs) under different patterns of use in a Mediterranean population and to explore the potential effect of symptomatic slow-acting drugs for osteoarthritis (SYSADOAs; chondroitin sulfate and glucosamine) and metamizole (or dipyrone), also reported to influence COX-2 activity.

METHODS

We performed a case-control study nested in a cohort extracted from the primary care database, BIFAP. From 2001 to 2014, we included 15 491 incident cases and 60 000 random controls. To estimate the association between the drugs of interest and CRC, we built logistic regression models to compute the adjusted-odds ratios (AOR) and 95% confidence intervals (CI).

RESULTS

NA-NSAIDs use was associated with a reduced risk of CRC (AOR = 0.67; 95% CI: 0.63-0.71) and increased linearly with duration of treatment (p for trend <0.001). The effect diminished upon discontinuation but persisted statistically significant up to 1 year. All individual NA-NSAIDs examined showed a decreased risk. The concomitant use of proton-pump inhibitors (PPI) had no impact on the protective effect of NA-NSAIDs; AOR_{PPI + NSAID}  = 0.64; 0.58-0.71. SYSADOA use was associated with a reduced risk (0.79; 0.69-0.90) but disappeared after the exclusion of NSAID users during the previous 1 or 3 years (0.85; 0.70-1.04 and 1.00; 0.76-1.31 respectively). Metamizole did not show a chemoprotective effect.

CONCLUSIONS

NA-NSAID use is associated with a duration-dependent risk reduction of CRC not shared by SYSADOAs or metamizole.

Active metabolites of dipyrone induce a redox-dependent activation of the ion channels TRPA1 and TRPV1

Introduction:

The nonopioid analgesic and antipyretic dipyrone (metamizol) is frequently used worldwide. Dipyrone is a prodrug, and the metabolites 4-N-methylaminoantipyrine (MAA) and 4-aminoantipyrine (AA) seem to induce analgesia and antipyresia in part by inhibiting cyclooxygenase. In mice, however, the analgesic effect of dipyrone also seems to depend on the ion channel TRPA1. In this study, we explored the effects of dipyrone and its active metabolites on recombinant and native TRPA1 and TRPV1 channels.

Methods:

Constructs human (h) TRPA1 and TRPV1 were expressed in HEK293 cells, and dorsal root ganglion neurons were isolated from adult mice. Effects of dipyrone, MAA, and AA were explored by means of whole-cell patch clamp recordings and ratiometric calcium imaging.

Results:

Dipyrone failed to activate both hTRPA1 and hTRPV1. However, both MAA and AA evoked small outwardly rectifying membrane currents and an increase of intracellular calcium in cells expressing hTRPA1 or hTRPV1. MAA also sensitized both channels and thus potentiated inward currents induced by carvacrol (hTRPA1) and protons (hTRPV1). MAA-induced activation was inhibited by the antioxidant 10-mM glutathione included in the pipette, and the mutant constructs hTRPA1-C621/C641/C665S and hTRPV1-C158A/C391S/C767S were insensitive to both MAA and AA. Mouse dorsal root ganglion neurons exhibited a marginal calcium influx when challenged with MAA.

Conclusion:

The metabolites MAA and AA, but not dipyrone itself, activate and sensitize the nociceptive ion channels TRPA1 and TRPV1 in a redox-dependent manner. These effects may be relevant for dipyrone-induced analgesia and antipyresia.

The use of dipyrone in the ICU is associated with acute kidney injury: A retrospective cohort analysis

BACKGROUND

Use of dipyrone (metamizole) in perioperative and ICU pain therapy remains controversial due to a lack of solid evidence weighing dipyrone benefit against its potential life-threatening complications. Although dipyrone has known analgesic and antipyretic properties, its mechanisms of actions are incompletely understood. Although dipyrone effects on renal vasodilator prostaglandin synthesis are documented, little is known about its potential renal side effects, especially in the critical care environment.

OBJECTIVE

Investigation of the perioperative nephrotoxic potential of dipyrone in patients prone to acute kidney injury (AKI).

DESIGN

Retrospective cohort study.

SETTING

Single centre study in a tertiary referral hospital from January 2013 until June 2013.

PATIENTS

A total of 500 consecutive patients aged 18 years and older referred to the anaesthesia ICU. Patients were excluded if admitted from or discharged to other ICUs, if referred for post resuscitation care, or if repeatedly admitted to the ICU.

MAIN OUTCOME MEASURES

Incidence of AKI, as defined by the Kidney Disease: Improving Global Outcomes Acute Kidney Injury Work Group criteria, and duration of vasopressor therapy.

RESULTS

Use of dipyrone was associated with an increased incidence of AKI in a dose-dependent manner with a 1.6-fold increase in the incidence of AKI with each additional gram of intravenous dipyrone per day. Dipyrone dose of more than 2.5 g day was the best risk predictive cut-off for AKI. Patients receiving dipyrone on the ICU presented with a prolonged duration of vasopressor therapy.

CONCLUSION

Increasing dipyrone dosage is a potential independent risk factor for AKI in adult ICU patients and may prolong vasopressor therapy. Clinical evidence for a benefit of dipyrone therapy in the ICU is insufficient and needs further critical evaluation.

Dipyrone (metamizole) markedly interferes with platelet inhibition by aspirin in patients with acute and chronic pain: A case-control study

BACKGROUND

Nonopioid analgesic drugs may interfere with platelet inhibition by aspirin. Recent in vitro and clinical studies in patients with cardiovascular disease have suggested that this pharmacodynamic interaction may also occur with dipyrone, a nonopioid analgesic popular in Europe, Asia and South America.

OBJECTIVE

Dipyrone is used extensively in acute and chronic pain. This study was undertaken to provide clinical data, so far missing, on its interactions in this group of patients.

DESIGN

A case-control study.

SETTING

Primary care in one European university hospital centre.

PATIENTS

In total, 27 patients with stable cardiovascular, cerebrovascular or peripheral arterial disease and acute or chronic pain were identified and given dipyrone for at least 5 days in combination with low-dose aspirin. In total, 10 comparable patients on low-dose aspirin alone served as controls.

MAIN OUTCOME MEASURES

Platelet-rich plasma was prepared to determine arachidonic acid-induced aggregation (aggregometry) and thromboxane formation (immunoassay). Platelet sensitivity to aspirin was examined in vitro. The presence of dipyrone (metabolites) in plasma was confirmed by HPLC. Additional in vitro measurements examined the aspirin/dipyrone interaction in healthy donors.

RESULTS

Inhibition of aggregation was observed in only six of 27 patients receiving aspirin with dipyrone, with absence of complete inhibition by antiplatelet therapy showing in 78% of patients. In contrast, aggregation was completely inhibited in nine of 10 control patients (P < 0.001). Platelet thromboxane synthesis was higher in patients receiving dipyrone + aspirin compared with controls (387 ± 89 vs. 7 ± 1 ng ml, P < 0.001). Aspirin added in vitro failed to inhibit aggregation and thromboxane synthesis in platelet-rich plasma from dipyrone-treated patients. In vitro measurements with blood from healthy individuals confirmed that dipyrone dramatically reduces inhibition of platelet thromboxane synthesis by aspirin.

CONCLUSIONS

Dipyrone given for 5 days or longer blunts platelet inhibition by low-dose aspirin in the majority of recipients.

TRIAL REGISTRATION

German Clinical Trials Register: DRKS ID DRKS00000204. Universal Trial Number (UTN): U1111-1113-3946.

Evaluation of hematological alterations after therapeutic use of dipyrone in healthy adults: a prospective study

Background Dipyrone is a non-narcotic analgesic/antipyretic widely used in some countries but prohibited in others due to suspected risk of agranulocytosis. The primary goal of this study was to evaluate hematological alterations in healthy adult volunteers after treatment with dipyrone. Methods The study enrolled 30 healthy volunteers of both genders, aged 19-37 years. They received tablets containing 500 mg of dipyrone sodium to be used four times daily for 7 consecutive days. Before the first administration, arterial pressure was measured and blood was collected in order to evaluate hematological baseline parameters. On the 8th day after the beginning of treatment, the volunteers had their blood pressure assessed once more and underwent a second blood draw. Total and specific leukocyte counts, creatinine, urea, aspartate aminotransferase (AST), alanine aminotransferase (ALT), erythrocytes, and platelets were quantitatively determined. Results No statistically significant difference was observed among total or specific leukocyte counts. Number of platelets, erythrocytes, hemoglobin, and hematocrit decreased after treatment. Diastolic pressure, mean arterial pressure (MAP), and urea concentration declined, while creatinine, AST, and ALT showed no significant alterations. It is noteworthy that, even for parameters that showed statistically significant changes, the highest and lowest values remained within the normal ranges. Conclusions Although dipyrone has historically been associated with agranulocytosis, leukocyte counts remained practically unchanged after oral administration of dipyrone. On the other hand, the present study adds evidence that dipyrone is able to produce statistically relevant decrease in number of platelets, erythrocytes, hemoglobin, and hematocrit in healthy adults, even after short-term treatment.

Postoperative pain management in children: Guidance from the pain committee of the European Society for Paediatric Anaesthesiology (ESPA Pain Management Ladder Initiative)

The main remit of the European Society for Paediatric Anaesthesiology (ESPA) Pain Committee is to improve the quality of pain management in children. The ESPA Pain Management Ladder is a clinical practice advisory based upon expert consensus to help to ensure a basic standard of perioperative pain management for all children. Further steps are suggested to improve pain management once a basic standard has been achieved. The guidance is grouped by the type of surgical procedure and layered to suggest basic, intermediate, and advanced pain management methods. The committee members are aware that there are marked differences in financial and personal resources in different institutions and countries and also considerable variations in the availability of analgesic drugs across Europe. We recommend that the guidance should be used as a framework to guide best practice.

Dipyrone is the preferred nonopioid analgesic for the treatment of acute and chronic pain. A survey of clinical practice in German-speaking countries

PURPOSE

Nonopioid analgesics are frequently used for the treatment of acute and chronic pain. Dipyrone is an alternative to NSAIDs and paracetamol, however, data on the frequency of its usage by anaesthesiologists in the perioperative and chronic pain setting are lacking and its adverse reactions are a matter of debate.

METHODS

The link to a questionnaire on the use of nonopioid analgesics (NSAIDs, COX-2 inhibitors, paracetamol, dipyrone) and the safety of dipyrone in the perioperative and chronic pain setting was mailed to anaesthesiologists and pain physicians.

RESULTS

A total of 2237 responses were analysed. About 97.4% of the respondents used nonopioid analgesics for the treatment of acute pain, with 93.8% administering dipyrone, 54.0% NSAIDs, 41.8% COX-2 inhibitors and 49.2% paracetamol. Nonopioid analgesics were administered preoperatively by 22.3%, intraoperatively by 86.1% and postoperatively by 73.0% of the respondents. For chronic pain management, 76.7% of the respondents prescribed oral dipyrone in combination with other nonopioid analgesics; 19.9% used dipyrone as sole nonopioid, whereas 2.9% denied its use. Cases of dipyrone-associated agranulocytosis were observed by 3.5% of the respondents of the acute and 1.5% of the chronic pain questionnaire, respectively. The majority of respondents (acute pain: 73.0%, chronic pain 59.3%) performed no blood cell counts to monitor dipyrone therapy. Patients were rarely informed about possible adverse drug reactions.

CONCLUSIONS

Dipyrone is the preferred nonopioid analgesic in the perioperative and chronic pain setting. Although cases of agranulocytosis occur, benefits apparently outweigh the risks according to anaesthesiologists. Measures like patient information may improve safety.

SIGNIFICANCE

A survey of anaesthesiologist in German-speaking countries revealed dipyrone as preferred nonopioid analgesic for the treatment of acute and chronic pain. Benefits seem to outweigh the risks, specifically the risk of agranulocytosis. Information of medical staff and patients on adverse drug reactions and symptoms of agranulocytosis should be implemented.

PK/PD modeling of flunixin meglumine in a kaolin-induced inflammation model in piglets

Flunixin is marketed in several countries for analgesia in adult swine but little is known about its efficacy in piglets. Thirty-two piglets (6-8 days old) were randomized to receive placebo saline (n = 11, group CONTROL) or flunixin meglumine intravenously at 2.2 (n = 11, group MEDIUM) or 4.4 (n = 10, group HIGH) mg/kg, 10 hr after subcutaneous injection of kaolin in the left metacarpal area. A hand-held algometer was used to determine each piglet's mechanical nociceptive threshold (MNT) from both front feet up to 50 hr after treatment (cut-off value of 24.5 newton). Serial venous blood samples were obtained to quantify flunixin in plasma using LC-MS/MS. A PKPD model describing the effect of flunixin on the mechanical nociceptive threshold was obtained based on an inhibitory indirect response model. A two-compartmental PK model was used. A significant effect of flunixin was observed for both doses compared to control group, with 4.4 mg/kg showing the most relevant (6-10 newton) and long-lasting effect (34 hr). The median IC50 was 6.78 and 2.63 mg/ml in groups MEDIUM and HIGH, respectively. The ED50 in this model was 6.6 mg/kg. Flunixin exhibited marked antinociceptive effect on kaolin-induced inflammatory hyperalgesia in piglets.

Oral nonsteroidal anti-inflammatory drugs (NSAIDs) for cancer pain in adults

BACKGROUND

Pain is a common symptom with cancer, and 30% to 50% of all people with cancer will experience moderate to severe pain that can have a major negative impact on their quality of life. Non-opioid drugs are commonly used to treat cancer pain, and are recommended for this purpose in the World Health Organization (WHO) cancer pain treatment ladder, either alone or in combination with opioids.A previous Cochrane review that examined the evidence for nonsteroidal anti-inflammatory drugs (NSAIDs) or paracetamol, alone or combined with opioids, for cancer pain was withdrawn in 2015 because it was out of date; the date of the last search was 2005. This review, and another on paracetamol, updates the evidence.

OBJECTIVES

To assess the efficacy of oral NSAIDs for cancer pain in adults, and the adverse events reported during their use in clinical trials.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase from inception to April 2017, together with reference lists of retrieved papers and reviews, and two online study registries.

SELECTION CRITERIA

We included randomised, double-blind, single-blind, or open-label studies of five days' duration or longer, comparing any oral NSAID alone with placebo or another NSAID, or a combination of NSAID plus opioid with the same dose of the opioid alone, for cancer pain of any pain intensity. The minimum study size was 25 participants per treatment arm at the initial randomisation.

DATA COLLECTION AND ANALYSIS

Two review authors independently searched for studies, extracted efficacy and adverse event data, and examined issues of study quality and potential bias. We did not carry out any pooled analyses. We assessed the quality of the evidence using GRADE and created a 'Summary of findings' table.

MAIN RESULTS

Eleven studies satisfied inclusion criteria, lasting one week or longer; 949 participants with mostly moderate or severe pain were randomised initially, but fewer completed treatment or had results of treatment. Eight studies were double-blind, two single-blind, and one open-label. None had a placebo only control; eight compared different NSAIDs, three an NSAID with opioid or opioid combination, and one both. None compared an NSAID plus opioid with the same dose of opioid alone. Most studies were at high risk of bias for blinding, incomplete outcome data, or small size; none was unequivocally at low risk of bias.It was not possible to compare NSAIDs as a group with another treatment, or one NSAID with another NSAID. Results for all NSAIDs are reported as a randomised cohort. We judged results for all outcomes as very low-quality evidence.None of the studies reported our primary outcomes of participants with pain reduction of at least 50%, and at least 30%, from baseline; participants with Patient Global Impression of Change (PGIC) of much improved or very much improved (or equivalent wording). With NSAID, initially moderate or severe pain was reduced to no worse than mild pain after one or two weeks in four studies (415 participants in total), with a range of estimates between 26% and 51% in individual studies.Adverse event and withdrawal reporting was inconsistent. Two serious adverse events were reported with NSAIDs, and 22 deaths, but these were not clearly related to any pain treatment. Common adverse events were thirst/dry mouth (15%), loss of appetite (14%), somnolence (11%), and dyspepsia (11%). Withdrawals were common, mostly because of lack of efficacy (24%) or adverse events (5%).

AUTHORS' CONCLUSIONS

There is no high-quality evidence to support or refute the use of NSAIDs alone or in combination with opioids for the three steps of the three-step WHO cancer pain ladder. There is very low-quality evidence that some people with moderate or severe cancer pain can obtain substantial levels of benefit within one or two weeks.