Peri-operative use of paracetamol

Population Pharmacokinetic Modeling and Dose Optimization of Acetaminophen and its Metabolites Following Intravenous Infusion in Critically ill Adults

BACKGROUND AND OBJECTIVE

Acetaminophen (paracetamol) is a ubiquitously administered drug in critically ill patients. Considering the dearth of literature, we evaluated the population pharmacokinetics of intravenous acetaminophen and its principal metabolites (sulfate and glucuronide) in this population.

METHODS

Critically ill adults receiving intravenous acetaminophen were included in the study. One to three blood samples were withdrawn per patient for the estimation of acetaminophen, and its metabolites (acetaminophen glucuronide and acetaminophen sulfate). High-performance liquid chromatography was used for measuring serum concentrations. We used nonlinear mixed-effect modeling for estimating the primary pharmacokinetic parameters of acetaminophen and its metabolites. The effect of covariates was evaluated followed by dose optimization using Monte Carlo simulation. Patient factors such as demographic information, liver and renal function tests were used as covariates in population pharmacokinetic analysis. The therapeutic range for serum acetaminophen concentration was considered to be 66-132 μM, while 990 μM was considered as the threshold for toxic concentration.

RESULTS

Eighty-seven participants were recruited. A joint two-compartment acetaminophen pharmacokinetic model linked to glucuronide and sulfate metabolite compartments was used. The central and peripheral volume distributions were 7.87 and 8.87 L/70 kg, respectively. Estimated clearance (CL) was 0.58 L/h/70 kg, while intercompartmental clearance was 44.2 L/h/70 kg. The glucuronide and sulfate metabolite CL were 22 and 94.7 L/h/70 kg, respectively. Monte Carlo simulation showed that twice-daily administration of acetaminophen would result in a relatively higher proportion of patient population achieving and retaining serum concentrations in the therapeutic range, with reduced risk of concentrations remaining in the toxic range.

CONCLUSION

A joint pharmacokinetic model for intravenous acetaminophen and its principal metabolites in a critically ill patient population has been developed. Acetaminophen CL in this patient population is reduced. We propose a reduction in the frequency of administration to reduce the risk of supra-therapeutic concentrations in this population.

Comparative Efficacy of Adjuvant Nonopioid Analgesia in Adult Cardiac Surgical Patients: A Network Meta-Analysis

OBJECTIVES

To compare the relative efficacy of adjuvant nonopioid analgesic regimens in adult cardiac surgical patients.

DESIGN

This frequentist, random-effects network meta-analysis (NMA) was prospectively registered on PROSPERO (CRD42021282913) and conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analyses for Network Meta-Analyses (PRISMA-NMA). The risk of bias (RoB) and confidence of evidence were assessed by RoB 2 and Confidence in Network Meta-Analysis, respectively. Relevant databases were searched from inception to October 9, 2021.

SETTING

A total of 124 (N = 26,257) randomized controlled trials were included, of which 110 were analyzed.

PARTICIPANTS

Trials enrolling adults (≥18 years of age) undergoing cardiac surgery that compared nonopioid analgesics against other nonopioid analgesics, placebo, or no additional treatment, as adjuvants to standard analgesic management, and reported at least 1 of the outcomes of interest.

MEASUREMENT AND MAIN RESULTS

Outcomes of interest included resting postoperative pain scores at 24 hours. Compared with standard care and/or placebo, pain scores were reduced significantly by 10 different regimens, including acetaminophen (N = 176; mean difference [MD] -0.66 points, 95% CI -1.16 to -0.15 points; high confidence), magnesium (N = 323; -0.05 points, 95% CI -0.07 to -0.02 points; high confidence), gabapentin (N = 96; MD -0.40 points, 95% CI -0.71 to -0.09; moderate confidence), and clonidine (N = 64; MD v0.38 points, 95% CI -0.73 to v0.04 points; moderate confidence). Indomethacin, diclofenac, magnesium, and gabapentin significantly reduced 24-hour opioid consumption. Four regimens significantly decreased the intensive care unit length of stay. Hydrocortisone, dexmedetomidine, and clonidine significantly decreased the duration of mechanical ventilation. Magnesium decreased, while methylprednisolone significantly increased, the risk of myocardial infarction.

CONCLUSIONS

Given the increasing emphasis on enhanced recovery after surgery(ERAS) protocols and the eventual goal of limiting opiate prescriptions postoperatively, the authors' data suggested far greater use of nonopioid adjuncts to minimize pain and enhance recovery following cardiac surgery.

Comparative evaluation of effect of different premedication agents on efficacy of Articaine: A randomized contol trial

Type of study

Original Research.

Aims

To comparatively evaluate the effect of different premedication agents on the efficacy of 4% Articaine in teeth with symptomatic irreversible pulpitis.

Materials and methods

The primary objective of our study is to evaluate the effect of premedication agents on efficacy of Articaine as an oral anesthetic. Our secondary objective is to comparatively evaluate the efficacy of Diclofenac patch, Ibuprofen tablet, Paracetamol tablet and Placebo as a premedication agent. Patients with 25-40 years age, no systemic disease, no history of medication for that complaint, with pain on Heft Parker Visual Analog Scale between 55 mm and 170 mm (VAS), no tenderness on percussion, cold test and EPT negative- Positive, giving proper consent, coming to the Department of Conservative Dentistry and Endodontics were allowed to participate. The exclusion criteria include the following- Non-vital teeth, pregnant and lactating women, allergic to Articaine and NSAIDs, active systemic disease, immune-compromised patients, taken analgesics in last 24 h, root fractures, restoration extending to pulp10 and periapical pathologies (except periodontal ligament widening).Preoperatively pain was recorded using Heft Parker VAS (Visual Analog Scale). Cold testing, palpation, percussion and EPT were carried out. 40 patients having symptomatic irreversible pulpitis were randomly divided into 4 groups: group 1 Placebo (n = 10), group 2-Diclofenac patch (n = 10), group-3 Ibuprofen tablets (n = 10), group 4-Paracetamol tablets (n = 10). After 1 h of premedication, all patients were administered IANB injection using 4% Articaine (Septanest with adrenaline 1/100000, Septodont, France) containing epinephrine 1:100000. 15 mins after administration of IANB, patients were asked about symptomatic numbness and was tested with Endo frost and EPT and Outcome was recorded. If lip numbness was present, Electric Pulp Testing and Cold Test give negative result then endodontic access opening was performed and pain was recorded using visual analog scale. The study was conducted for a period of 1.5 years.

Results

During the access cavity preparation only 1 subject in the Group III reported pain while in other groups none of the subjects reported pain of any type. When the intergroup comparison was made of intensity of pain 15 min after LA and during access cavity preparation, the difference between the groups was statistically non-significant when analyzed using One Way ANOVA. The intragroup comparison between three time intervals revealed significant reduction in the pain scores from the pre-treatment levels in all the four groups.

Conclusions

The results of the study showed that there is no significant effect of different premedication agents on the efficacy of 4% Articaine in teeth with symptomatic irreversible pulpitis.

Multimodal Analgesia

Perioperative pain management is one of the domains in which Anesthesiologists are intricately involved, and which is immensely important. Adequate postoperative analgesia is central to avoid both the acute as well as chronic complications of uncontrolled postoperative pain. Preventive analgesia has been identified as an approach to mitigate the phenomenon of central sensitization, which plays an important role in the development of chronic pain after surgery. As an over-reliance on opioids for peri- and postoperative pain control is associated with opioid dependence and hyperalgesia, multimodal analgesia has taken center stage. Multimodal analgesia, in theory, will optimize perioperative pain control, reduce the chance of central sensitization, and avoid the detrimental effects of opioid overuse. Multiple classes of systemic analgesic medications have been used to accomplish these tasks, and the aim of this article is to outline these medications, their mechanisms of action, as well as the evidence behind their individual roles in multimodal analgesia. Regional anesthesia has also been embraced as a key component of multimodal analgesia in orthopedic surgery; however, over the past several years, local infiltration analgesia (LIA) emerged as a viable alternative, particularly in total knee arthroplasty.

A green approach to the analysis of co-administered ampicillin/sulbactam and paracetamol in human urine

The novelty of this work is the simultaneous analysis of sulbactam (SUL), ampicillin (AMP), and paracetamol (PARA) in human urine samples, using the environmentally benign RP-HPLC method. A C18 column was used in chromatographic separation using potassium dihydrogen phosphate (10 mmol L^-1, pH 5)/ethanol (90 %, V/V) as the mobile phase; flow rate was 1.00 mL min^-1. UV detection at 220 nm was used for quantification. The proposed method showed good linearity in the concentration ranges of 2.20-250.00 μg mL^-1 for SUL, 2.50-250.00 μg mL^-1 for PARA, and 14.50-250.00 μg mL^-1 for AMP. Direct injection of urine samples with no prior extraction was performed. This method was found successful in moving towards greener studies of drugs' urinary excretion, by decreasing hazardous solvent consumption and waste. Moreover, the method was applied to investigate the urinary excretion of the drugs and possible interaction between ampicillin and paracetamol.

Regional anesthesia and acute perioperative pain management in thoracic surgery: a narrative review

Background and Objective

Thoracic surgery causes significant pain which can negatively affect pulmonary function and increase risk of postoperative complications. Effective analgesia is important to reduce splinting and atelectasis. Systemic opioids and thoracic epidural analgesia (TEA) have been used for decades and are effective at treating acute post-thoracotomy pain, although both have risks and adverse effects. The advancement of thoracoscopic surgery, a focus on multimodal and opioid-sparing analgesics, and the development of ultrasound-guided regional anesthesia techniques have greatly expanded the options for acute pain management after thoracic surgery. Despite the expansion of surgical techniques and analgesic approaches, there is no clear optimal approach to pain management. This review aims to summarize the body of literature regarding systemic and regional anesthetic techniques for thoracic surgery in both thoracotomy and minimally invasive approaches, with a goal of providing a foundation for providers to make individualized decisions for patients depending on surgical approach and patient factors, and to discuss avenues for future research.

Methods

We searched PubMed and Google Scholar databases from inception to May 2021 using the terms “thoracic surgery”, “thoracic surgery AND pain management”, “thoracic surgery AND analgesia”, “thoracic surgery AND regional anesthesia”, “thoracic surgery AND epidural”. We considered articles written in English and available to the reader.

Key Content and Findings

There is a wide variety of strategies for treating acute pain after thoracic surgery, including multimodal opioid and non-opioid systemic analgesics, regional anesthesia including TEA and paravertebral blocks (PVB), and a recent expansion in the use of novel fascial plane blocks especially for thoracoscopy. The body of literature on the effectiveness of different approaches for thoracotomy and thoracoscopy is a rapidly expanding field and area of active debate.

Conclusions

The optimal analgesic approach for thoracic surgery may depend on patient factors, surgical factors, and institutional factors. Although TEA may provide optimal analgesia after thoracotomy, PVB and emerging fascial plane blocks may offer effective alternatives. A tailored approach using multimodal systemic therapies and regional anesthesia is important, and future studies comparing techniques are necessary to further investigate the optimal approach to improve patient outcomes.

Paracetamol (acetaminophen) use in infants and children was never shown to be safe for neurodevelopment: a systematic review with citation tracking

Although widely believed by pediatricians and parents to be safe for use in infants and children when used as directed, increasing evidence indicates that early life exposure to paracetamol (acetaminophen) may cause long-term neurodevelopmental problems. Furthermore, recent studies in animal models demonstrate that cognitive development is exquisitely sensitive to paracetamol exposure during early development. In this study, evidence for the claim that paracetamol is safe was evaluated using a systematic literature search. Publications on PubMed between 1974 and 2017 that contained the keywords "infant" and either "paracetamol" or "acetaminophen" were considered. Of those initial 3096 papers, 218 were identified that made claims that paracetamol was safe for use with infants or children. From these 218, a total of 103 papers were identified as sources of authority for the safety claim.   Conclusion: A total of 52 papers contained actual experiments designed to test safety, and had a median follow-up time of 48 h. None monitored neurodevelopment. Furthermore, no trial considered total exposure to drug since birth, eliminating the possibility that the effects of drug exposure on long-term neurodevelopment could be accurately assessed. On the other hand, abundant and sufficient evidence was found to conclude that paracetamol does not induce acute liver damage in babies or children when used as directed. What is Known: • Paracetamol (acetaminophen) is widely thought by pediatricians and parents to be safe when used as directed in the pediatric population, and is the most widely used drug in that population, with more than 90% of children exposed to the drug in some reports. • Paracetamol is known to cause liver damage in adults under conditions of oxidative stress or when used in excess, but increasing evidence from studies in humans and in laboratory animals indicates that the target organ for paracetamol toxicity during early development is the brain, not the liver. What is New: • This study finds hundreds of published reports in the medical literature asserting that paracetamol is safe when used as directed, providing a foundation for the widespread belief that the drug is safe. • This study shows that paracetamol was proven to be safe by approximately 50 short-term studies demonstrating the drug's safety for the pediatric liver, but the drug was never shown to be safe for neurodevelopment. Paracetamol is widely believed to be safe for infants and children when used as directed, despite mounting evidence in humans and in laboratory animals indicating that the drug is not safe for neurodevelopment. An exhaustive search of published work cited for safe use of paracetamol in the pediatric population revealed 52 experimental studies pointing toward safety, but the median follow-up time was only 48 h, and neurodevelopment was never assessed.

Comparison of intravenous and oral administration of acetaminophen in adults undergoing general anesthesia

BACKGROUND

Acetaminophen is a widely clinically used analgesic. However, the clinical effect of the route of administration on postoperative analgesia as well as on postoperative nausea and vomiting in patients undergoing general anesthesia remains unclear. This study aimed to explore whether the route of administration of acetaminophen affects postoperative analgesia, nausea, and vomiting in patients undergoing general anesthesia.

METHODS

We included all randomized controlled trials investigating the effects of the route of administration of acetaminophen on postoperative pain, nausea, and vomiting in patients undergoing general anesthesia. Independent examiners reviewed the literature and extracted data, with disagreements resolved through negotiation or the involvement of a third party. The Cochrane risk assessment tool was used to evaluate the quality of the included randomized controlled trials. A narrative synthesis was conducted to summarize the qualitative information from the included studies. A meta-integration of quantitative data was performed using RevMan 5.4.

RESULTS

Ten studies met the inclusion criteria. Eight studies assessed postoperative pain, whereas two assessed postoperative nausea and vomiting. Data from the eight studies assessing postoperative pain confirmed that there was no difference between intravenously and orally administered acetaminophen in adults (OR = -0.13; 95% CI, -0.36 to 0.11; p = 0.3). Data from the two studies assessing postoperative nausea and vomiting revealed no difference between intravenously and orally administered acetaminophen in adults (OR = 0.89; 95% CI, 0.64-1.25; p = 0.51). The included studies were of poor quality, with a heterogeneity of 68%.

CONCLUSIONS

No differences in postoperative analgesia or postoperative nausea and vomiting were observed between the routes of administration (intravenous vs. oral) of acetaminophen in adult patients undergoing general anesthesia. There is a need for future large sample studies to increase the reliability of the results.

Evaluation of urinary acetaminophen metabolites and its association with the genetic polymorphisms of the metabolising enzymes, and serum acetaminophen concentrations in preterm neonates with patent ductus arteriosus

Acetaminophen is gaining importance as a first-line drug for treating patent ductus arteriosus (PDA) in neonates. Predominant metabolites of acetaminophen in preterm neonates vary from that of adults; and the drug is predominantly metabolised by conjugation and partly by Cytochrome P450 (CYP) enzymes.We carried out the present study to identify the principal urine metabolites of acetaminophen (glucuronide/sulphate) in preterm neonates with hemodynamically significant PDA receiving intravenous acetaminophen, and to evaluate the prevalence of single nucleotide polymorphisms (SNPs) in the key CYP enzymes (CYP1A2*3, CYP1A2*4, CYP1A2*1C, CYP1A2*1K, CYP1A2*6, CYP2D6*10, CYP2E1*2, CYP2E1*5B, CYP3A4*1B, CYP3A4*2, CYP3A4*3, CYP3A5*3, CYP3A5*7, and CYP3A5*11) and their effect on urinary metabolites and serum acetaminophen concentrations.Nineteen (32.8%) neonates had heterozygous CYP1A2*1C, two (3.3%) with heterozygous CYP1A2*1K, 15 (27.8%) and two (3.7%) had heterozygous and homozygous CYP2D6*10, two (3.7%) had heterozygous CYP2E1*5B, seven (12.3%) and three (5.3%) had heterozygous and homozygous CYP3A4*1B, and three (5.5%) had CYP3A5*7 amongst the study population. Acetaminophen sulphate predominated over glucuronide metabolite at all time points. Postnatal days of life was significantly associated with an increase in the urine acetaminophen metabolites with decreased serum acetaminophen concentrations.A significant prevalence of SNPs in the key CYP enzymes related to acetaminophen metabolism was observed in our neonatal population. Population pharmacokinetic-pharmacodynamic modelling incorporating genetic and metabolite data is urgently needed for implementation of precision medicine in this vulnerable population.

Preventive Analgesia, Hemodynamic Stability, and Pain in Vitreoretinal Surgery

Background and Objectives: Although vitreoretinal surgery (VRS) is most commonly performed under regional anaesthesia (RA), in patients who might be unable to cooperate during prolonged procedures, general anaesthesia (GA) with intraprocedural use of opioid analgesics (OA) might be worth considering. It seems that the surgical pleth index (SPI) can be used to optimise the intraprocedural titration of OA, which improves haemodynamic stability. Preventive analgesia (PA) is combined with GA to minimise intraprocedural OA administration. Materials and Methods: We evaluated the benefit of PA combined with GA using SPI-guided fentanyl (FNT) administration on the incidences of PIPP (postprocedural intolerable pain perception) and haemodynamic instability in patients undergoing VRS (p < 0.05). We randomly assigned 176 patients undergoing VRS to receive GA with SPI-guided FNT administration alone (GA group) or with preventive topical 2% proparacaine (topical anaesthesia (TA) group), a preprocedural peribulbar block (PBB) using 0.5% bupivacaine with 2% lidocaine (PBB group), or a preprocedural intravenous infusion of 1.0 g of metamizole (M group) or 1.0 g of paracetamol (P group). Results: Preventive PBB reduced the intraprocedural FNT requirement without influencing periprocedural outcomes (p < 0.05). Intraprocedural SPI-guided FNT administration during GA resulted in PIPP in 13.5% of patients undergoing VRS and blunted the periprocedural effects of preventive intravenous and regional analgesia with respect to PIPP and haemodynamic instability. Conclusions: SPI-guided FNT administration during GA eliminated the benefits of preventive analgesia in the PBB, TA, M, and P groups following VRS.

A systematic review and trial sequential analysis of intravenous vs. oral peri-operative paracetamol

Postoperative pain might be different after intravenous vs. oral paracetamol. We systematically reviewed randomised controlled trials in patients >15 years that compared intravenous with oral paracetamol for postoperative pain. We identified 14 trials with 1695 participants. There was inconclusive evidence for an effect of route of paracetamol administration on postoperative pain at 0–2 h (734 participants), 2–6 h (766 participants), 6–24 h (1115 participants) and >24 h (248 participants), with differences in standardised mean (95%CI) pain scores for intravenous vs. oral of −0.17 (−0.45 to 0.10), −0.09 (−0.24 to 0.06), 0.06 (−0.12 to 0.23) and 0.03 (−0.22 to 0.28), respectively. Trial sequential analyses suggested that a total of 3948 participants would be needed to demonstrate a meaningful difference in pain or its absence at 0–2 h. There were no differences in secondary outcomes. Intravenous paracetamol is more expensive than oral paracetamol. Substitution of oral paracetamol in half the patients given intravenous paracetamol in our hospital would save around £ 38,711 (€ 43,960 or US$ 47,498) per annum.

Spectrophotometric and Multivariate Calibration Techniques for Simultaneous Determination of Different Drugs in Pharmaceutical Formulations and Human Urine: Evaluation of Greenness Profile

Eco-friendly, rapid, and cost-effective two spectrophotometric methods were developed and validated for the determination of atenolol, paracetamol, hydrochlorothiazide, and levofloxacin. The first method is the newly developed extended derivative ratio (EDR) and the second method is multivariate curve resolution-alternating least squares (MCR-ALS). In the EDR method, the extended derivative ratio amplitudes at 281.6, 237.6, 279.2, and 282.8 nm were used for quantification of atenolol, paracetamol, hydrochlorothiazide, and levofloxacin, respectively. In the MCR-ALS method, calibration model was developed and correlation constraint was employed. External validation data set composed of seven mixtures was used, and different figures of merits such as root mean square error of prediction, standard error of prediction, bias, and relative error of prediction were calculated, and satisfactory results were obtained. Both methods provided comparable results. The methods were validated and applied for the determination of the target analytes in dosage forms, spiked and real human urine. Thereafter, the obtained results were statistically compared to the published methods and revealed no significant difference regarding accuracy and precision. Furthermore, the greenness profile of the methods was evaluated using the National Environmental Methods Index "NEMI" and Analytical Eco-Scale. The developed methods can be used as a valid eco-friendly and simple cost-effective alternative to the commonly used chromatographic methods for the routine analysis of the studied drugs in dosage forms and human urine.

Paracetamol as a basic component of a modern approach to adequate perioperative analgesia

The problem of adequate perioperative anesthesia is one of the most pressing in the current health care system, given its medical, humanistic and socio-economic aspects. Currently, the standard of postoperative analgesia is multimodal analgesia (MMA). One of the major and required components of MMA is paracetamol, which has antipyretic and analgesic effects with limited peripheral anti-inflammatory activity. Most authors consider intravenous paracetamol as a base drug in a multimodal analgesia strategy for a variety of surgical interventions, which reduces the need for opioids and reduces the side effects of the latter, which in turn significantly affects the results of treatment and the length of hospital stay.Numerous studies in many countries have created a broad evidence base for the clinical use of this drug. Due to its pharmacokinetic and pharmacodynamic properties, it has been shown that intravenous paracetamol has several advantages over oral and rectal forms: early and more effective onset of analgesia and stable maintenance of the therapeutic dose of paracetamol are explained by the formation of a faster and higher peak in the concentration of the drug. The side effects of using paracetamol can be compared with placebo. The mechanism of action of the drug is different from the mechanism of action of NSAIDs, however, is still not fully understood. It may possibly involve inhibition of cyclooxygenase, cannabinoid, or nitric oxide pathways in the central nervous system. Intravenous paracetamol is a safe and effective first-line drug for the treatment of moderate pain in the perioperative period.

Investigation of plasma concentrations of paracetamol, metacetamol, and orthocetamol in Japanese racehorses using liquid chromatography-electrospray ionisation-tandem mass spectrometry

Paracetamol is used widely as an over-the-counter analgesic and antipyretic medication for humans, but not for Japanese racehorses. Paracetamol can be an environmental substance, and is found together with its two isomers, metacetamol and orthocetamol, in equine urine. However, the sources and routes of paracetamol exposure remain unclear. To control the misuse of paracetamol, it is appropriate to establish residue limits for paracetamol to differentiate the administration of paracetamol from its environmental levels. In this study, we developed and validated a quantitative method for paracetamol, metacetamol, and orthocetamol in equine plasma using liquid chromatography-electrospray ionization-tandem mass spectrometry and applied it to postrace samples from 320 Japanese racehorses for approximately 1 year. In addition, we conducted feed analysis and related pharmacokinetics simulations to evaluate the contributions from exposure via feed. The hydrolyzed plasma concentrations of paracetamol, metacetamol, and orthocetamol ranged from 0.787 to 39.8 ng/mL (median 5.87 ng/mL), 0 to 2.13 ng/mL (0.347 ng/mL), and 1.98 to 82.8 ng/mL (16.6 ng/mL), respectively. Such low concentrations of paracetamol were deemed irrelevant to therapeutic effect. Based on statistical analysis, the preliminary Japanese residue limits of unhydrolyzed and hydrolyzed paracetamol were determined to be 70.5 ng/mL and 112 ng/mL, respectively, in plasma, at a risk factor of 1 in 10,000. Furthermore, we detected paracetamol and orthocetamol in feed samples. A pharmacokinetics simulation showed that the presence of orthocetamol is most probably related to daily feed rations. As for paracetamol, feed can be one of the sources and other possible sources require further investigation.

Impact of Pre-Emptive Intravenous Ibuprofen on Perioperative Analgesia in Patients Undergoing Third Molar Extraction: A Randomised Controlled Study

Objective

The aim of the present study was to evaluate the analgesic efficacy of pre-emptive intravenous (iv) ibuprofen on pain during and after the mandibular third molar surgery.

Methods

A total of 60 patients were included in the study. They were allocated as ibuprofen 800 mg iv+dexketoprofen 50 mg (group 1), ibuprofen 800 mg iv alone (group 2) or placebo (group 3). A local anaesthetic infiltration was administered to all patients. In all patients, haemodynamic values (mean arterial pressure (MAP) and heart rate (HR)) were recorded preoperatively, and infusions were started. State-Trait Anxiety Inventory (STAI) scale was used to assess anxiety states. Surgery started 15 min after the infusion. Haemodynamic values and pain scores with visual analogue scale (VAS) were recorded. Pain scores were recorded postoperatively at rest (VASR) and swallowing (VASS).

Results

There was no significant difference in the preoperative STAI values between the groups (p>0.05). HR, MAP and VAS pain scores were significantly higher in group 3 than in groups 1 and 2 (p<0.05). VASR and VASS scores were significantly higher in group 3 than in group 1 in the first 4 h postoperatively (p<0.05). VASS scores were significantly higher in group 3 than in group 2 at 1-4 h postoperatively (p<0.05), but there was no difference in VASR and VASS scores at 48 h after surgery.

Conclusion

Ibuprofen alone or in combination with dexketoprofen provided similar analgesia in the perioperative period when administered pre-emptively.

Pain Management After Surgical Tonsillectomy: Is There a Favorable Analgesic?

The aim of this study was to examine how ibuprofen and paracetamol prevent pain after cold-steel extracapsular tonsillectomy in children. Also, we examined the relation between age, gender, nausea, postoperative bleeding, antibiotic use, type of diet, and postoperative pain intensity and the type of administered analgesic. A prospective study was conducted on 147 children (95 males and 52 females, aged 7-17 years) who underwent tonsillectomy in the Clinical-Hospital Center "Dragiša Mišović" from January 1 to June 30, 2016. The degree of pain was measured using a visual analog scale (VAS). We did not observe any significant differences in postoperative nausea, hospitalization rate postoperative bleeding, and antibiotic use between the paracetamol and ibuprofen groups. A test of within-patient effects showed that VAS scores changed significantly during the postoperative follow-up period (P = .00), but there were no significant differences between the groups (P = .778). After 12 hours, 29.3% of the patients on paracetamol and 21.8% on ibuprofen were transferred to a soft diet; after 24 hours, 84.8% of the paracetamol group and 85.5% of the ibuprofen group were on a soft diet (χ² test, P < .05). There was a statistically significant correlation between VAS scores measured 4 hours after the surgery and the time of transference to the soft diet (Spearman ρ test, P < .001). The transfer to soft and normal diets was not significantly different between the 2 groups as assessed by the VAS scores (Pearson χ² test, P = .565).There is still no consensus on the most effective postoperative pain-control regiment after tonsillectomy. This study showed that satisfactory pain management was achieved equally with both paracetamol and ibuprofen.

Pharmacokinetics and safety of repeated oral dosing of acetaminophen in adult horses

BACKGROUND

There are no published studies on the pharmacokinetics of acetaminophen at the dosage used clinically (20 mg/kg), nor has the safety of multiple doses in horses been investigated.

OBJECTIVE

Define the pharmacokinetic parameters of oral acetaminophen at 20 mg/kg in adult horses as a single dose, and twice daily for 14 days to assess the safety of multiple dosing.

STUDY DESIGN

Pharmacokinetic study, multiple dose safety study.

METHODS

Eight healthy Thoroughbred geldings were given acetaminophen (20 mg/kg; 500 mg tablets) orally as a single dose followed by doses every 12 h for 14 days. Serial blood samples were collected for determination of plasma acetaminophen concentrations using high performance liquid chromatography with ultraviolet detection. Serum biochemical analysis, gastroscopy and liver biopsy were examined during the safety study.

RESULTS

Following a single dose, mean maximum concentration (C_max ) was 16.61 μg/mL at 1.35 h (T_max ), and drug concentration was below the lower limit of detection in most horses by 24 h. Elimination half-life (T_1/2 ) was 2.78 h. No significant accumulation was noted following multiple doses. Average C_max of acetaminophen following multiple oral dosing was 15.85 μg/mL, with a T_max of 0.99 h and T_1/2 of 4 h. Serum activities of sorbitol dehydrogenase were significantly decreased and total bilirubin concentrations were significantly increased following the last dose. No statistically significant changes were noted in gastroscopy scores.

MAIN LIMITATIONS

Only one dose level (20 mg/kg) was studied, sample size was small and only a single breed and sex was used, with no pretreatment liver biopsies.

CONCLUSION

This study described the pharmacokinetics of acetaminophen following single and multiple 20 mg/kg oral doses in adult horses and demonstrated the safety of acetaminophen with multiple oral dosing over 14 days. The summary is available in Portuguese - see Supporting information.

Scheduled Intravenous Acetaminophen Improves Patient Satisfaction With Postcraniotomy Pain Management: A Prospective, Randomized, Placebo-controlled, Double-blind Study

BACKGROUND

Postcraniotomy pain can be difficult to manage with opioids due to opioid-related side effects, including drowsiness, nausea/vomiting, confusion, and pupillary changes, potentially masking the signs of postoperative neurological deterioration. Intravenous (IV) acetaminophen, a nonopioid analgesic, has been reported to have opioid-sparing effects after abdominal and orthopedic surgeries. This study investigates whether IV acetaminophen has similar effects after craniotomy.

MATERIALS AND METHODS

In this prospective, randomized, placebo-controlled, double-blind clinical trial, 100 adult patients scheduled to undergo supratentorial craniotomy for excision of a brain mass were randomized to receive either IV acetaminophen or placebo preincision and then every 6 hours for a total of 24 hours after surgery. Total 24-hour opioid consumption, pain scores, satisfaction with overall pain management, time to meet postanesthesia care unit discharge criteria, and incidence of opioid-related side effects were compared.

RESULTS

There was no difference in the 24-hour postoperative opioid consumption in morphine equivalents between the IV acetaminophen group (median, 11 mg; n=45) and the placebo group (median, 10.1 mg; n=41). No statistically significant difference of visual analog scale pain score was observed between 2 treatment groups. Patient satisfaction with overall postoperative pain management was significantly higher in the IV acetaminophen group than the placebo group on a 1 to 10 scale (8.1±0.4 vs. 6.9±0.4; P=0.03). There was no significant difference in secondary outcomes, including the incidence of opioid-related side effects.

CONCLUSIONS

IV acetaminophen, as adjunctive therapy for craniotomy procedures, did not show an opioid-sparing effect in patients for the 24 hours after craniotomy; however, it was associated with improved patient satisfaction regarding overall pain control.

Supra-Therapeutic Oral Paracetamol Overdose in Adults: An Update for the Dental Team

Paracetamol (acetaminophen) is a commonly used analgesic; its 'over the counter' availability, low cost and popularity amongst patients often make it the first choice for dental pain. It is in this that its potential toxicity, made more complicated by the ever extending range of paracetamol-containing products, make the understanding of this medication key to the safe management of patients presenting to surgery with dental pain. Clinical relevance: The purpose of this article is to supply dental practitioners with the knowledge to manage patients who present having taken an oral supra-therapeutic paracetamol overdose. Consideration is given to those patients who can be treated safely in primary care and to those who require transfer to Accident and Emergency (A&E).

Adherence to Swedish guidelines for pain treatment in relation to pediatric tonsil surgery: A survey of the multidisciplinary team

BACKGROUND

Pain management in children after tonsil surgery is essential, and optimal pain treatment has been discussed for many years. Data from the National Tonsil Register in Sweden (NTRS) and a national mapping have demonstrated the need for national pain treatment guidelines for pediatric tonsil surgery. As a result, Swedish national guidelines, together with updated patient information on the website tonsilloperation.se, were developed and implemented in 2013.

OBJECTIVES

The objective of this study was to evaluate the professionals' opinions of and adherence to pain treatment guidelines for pediatric tonsil surgery patients in a two-year follow-up.

METHOD

This descriptive cross-sectional study was based on data from an inter-professional questionnaire, which was validated by an expert group using a content validity index (S-CVI 0.93). The questionnaire was sent to all Swedish ear, nose and throat (ENT) departments (n = 49) that the NTRS identified as performing tonsil surgery on children younger than 18 years of age. In each clinic, we asked for responses from staff in each of the following professions: ENT physicians, anesthesia physicians, registered nurse anesthetists, and registered nurses in the ENT departments.

RESULTS

Respondents from 48 ENT departments participated, and 139/163 (85%) completed questionnaires were returned. The guidelines were reported as being clear, ensuring patient safety and providing optimal pharmacological treatment. Treatment was given according to the guidelines: Half of the departments gave pre- or intraoperative treatment with clonidine, betamethasone and high-dose paracetamol (acetaminophen). A multimodal pain approach (paracetamol and COX-inhibitors) after hospital discharge was prescribed by all departments after tonsillectomy and, extensively, after tonsillotomy. One-third of the departments prescribed paracetamol with a higher normal dose for the first three postoperative days. Half of the departments prescribed rescue analgesics, clonidine or opioids after tonsillectomy. None of the departments prescribed codeine or tramadol, drugs that are discouraged in the guidelines. The majority of the departments used the website tonsilloperation.se to provide information to the patients and their caregivers.

CONCLUSION

The respondents' opinions of and the ENT departments adherence to the Swedish national guidelines were considered to be good. The national implementation process in Sweden has impacted the manner in which ENT departments treat pain after tonsil surgery.

Paracetamol: overdose-induced oxidative stress toxicity, metabolism, and protective effects of various compounds in vivo and in vitro

Paracetamol (APAP) is one of the most widely used and popular over-the-counter analgesic and antipyretic drugs in the world when used at therapeutic doses. APAP overdose can cause severe liver injury, liver necrosis and kidney damage in human beings and animals. Many studies indicate that oxidative stress is involved in the various toxicities associated with APAP, and various antioxidants were evaluated to investigate their protective roles against APAP-induced liver and kidney toxicities. To date, almost no review has addressed the APAP toxicity in relation to oxidative stress. This review updates the research conducted over the past decades into the production of reactive oxygen species (ROS), reactive nitrogen species (RNS), and oxidative stress as a result of APAP treatments, and ultimately their correlation with the toxicity and metabolism of APAP. The metabolism of APAP involves various CYP450 enzymes, through which oxidative stress might occur, and such metabolic factors are reviewed within. The therapeutics of a variety of compounds against APAP-induced organ damage based on their anti-oxidative effects is also discussed, in order to further understand the role of oxidative stress in APAP-induced toxicity. This review will throw new light on the critical roles of oxidative stress in APAP-induced toxicity, as well as on the contradictions and blind spots that still exist in the understanding of APAP toxicity, the cellular effects in terms of organ injury and cell signaling pathways, and finally strategies to help remedy such against oxidative damage.

Pharmacokinetic Study of Intravenous Acetaminophen Administered to Critically Ill Multiple-Trauma Patients at the Usual Dosage and a New Proposal for Administration

The pharmacokinetic profile of intravenous acetaminophen administered to critically ill multiple-trauma patients was studied after 4 consecutive doses of 1 g every 6 hours. Eleven blood samples were taken (predose and 15, 30, 45, 60, 90, 120, 180, 240, 300, and 360 minutes postdose), and urine was collected (during 6-hour intervals between doses) to determine serum and urine acetaminophen concentrations. These were used to calculate the following pharmacokinetic parameters: maximum and minimum concentrations, terminal half-life, area under serum concentration-time curve from 0 to 6 hours, mean residence time, volume of distribution, and serum and renal clearance of acetaminophen. Daily doses of acetaminophen required to obtain steady-state minimum (bolus dosing) and average plasma concentrations (continuous infusion) of 10 μg/mL were calculated (10 μg/mL is the presumed lower limit of the analgesic range). Data are expressed as median [interquartile range]. Twenty-two patients were studied, mostly young (age 44 [34-64] years) males (68%), not obese (weight 78 [70-84] kg). Acetaminophen concentrations and pharmacokinetic parameters were these: maximum concentration 33.6 [25.7-38.7] μg/mL and minimum concentration 0.5 [0.2-2.3] μg/mL, all values below 10 μg/mL and 8 below the detection limit; half-life 1.2 [1.0-1.9] hours; area under the curve for 6 hours 34.7 [29.7-52.7] μg·h/mL; mean residence time 1.8 [1.3-2.6] hours; steady-state volume of distribution 50.8 [42.5-66.5] L; and serum and renal clearance 28.8 [18.9-33.7] L/h and 15 [11-19] mL/min, respectively. Theoretically, daily doses for a steady-state minimum concentration of 10 μg/mL would be 12.2 [7.8-16.4] g/day (166 [112-202] mg/[kg·day]); for an average steady-state concentration of 10 μg/mL, they would be 6.9 [4.5-8.1] g/day (91 [59-111] mg/[kg·day]). In conclusion, administration of acetaminophen at the recommended dosage of 1 g per 6 hours to critically ill multiple-trauma patients yields serum concentrations below 10 μg/mL due to increased elimination. To reach the 10 μg/mL target, and from a strictly pharmacokinetic point of view, continuous infusion may be more feasible than bolus dosing. Such a change in dosing strategy requires appropriate, pharmacokinetic-pharmacodynamic and specific safety study.

Reduced anaesthetic requirements and postoperative analgesics in patients undergoing laparoscopic cholecystectomy: premedication with intravenous paracetamol versus ketorolac, a double blind and randomised clinical trial

OBJECTIVE

To compare the effects of premedication with intravenous paracetamol versus ketorolac, in decreasing intraoperative anaesthetic and postoperative opioid analgesics requirements in patients undergoing laparoscopic cholecystectomy.

METHOD

An experimental, prospective, comparative, double blind, and randomised clinical trial was conducted to determine intraoperative opioid requirements, and pain and analgesic requirements in the postoperative period in 100 healthy patients undergoing laparoscopic cholecystectomy. They were randomised into 2 groups: Group 1: pre-medicated with paracetamol 1g, and Group 2: with ketorolac 30mg (both administered intravenously 30minutes prior to surgery).

RESULTS

There were no statistically significant differences between groups as regards intraoperative remifentanil use (Group 1: 0.0739±0.016μg/kg/min, Group 2: 0.0741±0.018μg/kg/min). The number of patients in Group 2 that had values of VAS>4 points (22.4%) was lower than in Group 1 (28.6%), but with no statistically significant difference. Of the patients who needed postoperative opioid rescue, most required a single rescue and application of analgesics during hospitalisation, that prevailed between 3 and 12hours, without any significant differences between groups. No adverse effects were observed in the study sample.

CONCLUSION

Paracetamol 1g IV given preoperatively decreased anaesthetic requirements and the need for postoperative analgesics similar to the preoperative administration of ketorolac 30mg IV.

Identifying adults at risk of paracetamol toxicity in the acute dental setting: development of a clinical algorithm

Paracetamol is widely used and effective for the management of dental pain in the UK. Acute dental pain is a recognised precipitant of unintentional paracetamol overdose and in a small but significant number of cases this results in hepatotoxicity. Patients' understanding of the risks of excess paracetamol ingestion remains poor and risk of over-medication before presentation is increased due to a variety of factors including dental anxiety and fragmented provision of dental emergency services. Early recognition of overdose is crucial to preventing significant hepatotoxicity and death. Dentists have a role to play in recognising unintentional overdose cases and directing patients timeously to appropriate medical care. Guidelines on the treatment of paracetamol toxicity are readily available but our data suggests some dental settings may present a weak link in the care pathway and overdose may not be readily recognised. We have developed an algorithm and training package targeted at dentists in the acute dental setting with the aim of improving recognition of paracetamol toxicity in adults and directing onward referral appropriately. This paper also revises the key pharmacokinetics and pharmacodynamics of paracetamol and is intended to raise awareness of issues of toxicity for dentists.

[Pediatric perioperative systemic pain therapy: Austrian interdisciplinary recommendations on pediatric perioperative pain management]

BACKGROUND

Many analgesics used in adult medicine are not licensed for pediatric use. Licensing limitations do not, however, justify that children are deprived of a sufficient pain therapy particularly in perioperative pain therapy. The treatment is principally oriented to the strength of the pain. Due to the degree of pain caused, intramuscular and subcutaneous injections should be avoided generally.

NON-OPIOIDS

The basis of systemic pain therapy for children are non-opioids and primarily non-steroidal anti-inflammatory drugs (NSAIDs). They should be used prophylactically. The NSAIDs are clearly more effective than paracetamol for acute posttraumatic and postoperative pain and additionally allow economization of opioids. Severe side effects are rare in children but administration should be carefully considered especially in cases of hepatic and renal dysfunction or coagulation disorders. Paracetamol should only be taken in pregnancy and by children when there are appropriate indications because a possible causal connection with bronchial asthma exists. To ensure a safe dosing the age, body weight, duration of therapy, maximum daily dose and dosing intervals must be taken into account. Dipyrone is used in children for treatment of visceral pain and cholic. According to the current state of knowledge the rare but severe side effect of agranulocytosis does not justify a general rejection for short-term perioperative administration.

OPIOIDS

In cases of insufficient analgesia with non-opioid analgesics, the complementary use of opioids is also appropriate for children of all age groups. They are the medication of choice for episodes of medium to strong pain and are administered in a titrated form oriented to effectiveness. If severe pain is expected to last for more than 24 h, patient-controlled anesthesia should be implemented but requires a comprehensive surveillance by nursing personnel.

KETAMINE

Ketamine is used as an adjuvant in postoperative pain therapy and is recommended for use in pediatric sedation and analgosedation.

Swedish guidelines for the treatment of pain in tonsil surgery in pediatric patients up to 18 years

BACKGROUND

Surgery of the tonsils often causes severe pain lasting for many days as been shown by data from the National Tonsil Surgery Register in Sweden. Tonsillotomy is associated with fewer readmissions due to bleeding, number of days requiring analgesics and health care contacts due to pain compared to tonsillectomy. The register data demonstrate the necessity of better-evidenced based pain treatment guidelines for tonsil-surgery.

OBJECTIVES

To develop evidenced based pain treatment guidelines for tonsil-surgery in Sweden.

METHODS

The evidence based guidelines were designed by an updated literature review and from the clinical expertise in the pediatric pain field, which thereafter were reviewed by ENT-doctors and anesthetists from each ENT-clinic in Sweden.

RESULTS

A multimodal pain treatment approach is advocated, including premedication and administration during anesthesia, with paracetamol (acetaminophen), clonidine and betamethasone. If not given as a premedication the combination can be administered intravenously in the initial phase of anesthesia. At the end of surgery, if no bleeding problems, cox-inhibitors can be given. After discharge from hospital, the recommendations for pain relief are paracetamol combined with cox-inhibitors (ibuprofen, diclofenac) and if needed oral clonidine in favor of opioids. When pain intensity decreases, discontinue the analgesic treatment in the following order: opioid, clonidine, paracetamol and at last ibuprofen. The need for analgesic treatment after tonsillectomy is usually 5-8 days, after tonsillotomy only 3-5 days. Parents are recommended to contact the hospital if the child has difficulties in drinking or eating adequately and/or suffers from pain despite taking the recommended medication regularly.

CONCLUSIONS

Swedish guidelines for tonsil-surgery provide practical evidence-based pain treatment recommendations.

Intravenous non-opioid analgesia for peri- and postoperative pain management: a scientific review of intravenous acetaminophen and ibuprofen

Pain is a predictable consequence following operations, but the management of postoperative pain is another challenge for anesthesiologists and inappropriately controlled pain may lead to unwanted outcomes in the postoperative period. Opioids are indeed still at the mainstream of postoperative pain control, but solely using only opioids for postoperative pain management may be connected with risks of complications and adverse effects. As a consequence, the concept of multimodal analgesia has been proposed and is recommended whenever possible. Acetaminophen is one of the most commonly used analgesic and antipyretic drug for its good tolerance and high safety profiles. The introduction of intravenous form of acetaminophen has led to a wider flexibility of its use during peri- and postoperative periods, allowing the early initiation of multimodal analgesia. Many studies have revealed the efficacy, safety and opioid sparing effects of intravenous acetaminophen. Intravenous ibuprofen has also shown to be well tolerated and demonstrated to have significant opioid sparing effects during the postoperative period. However, the number of randomized controlled trials confirming the efficacy and safety is small and should be used in caution in certain group of patients. Intravenous acetaminophen and ibuprofen are important options for multimodal postoperative analgesia, improving pain and patient satisfaction.

OFIRMEV: an old drug becomes new again

This was judged to be the first place winning submission for the American Dental Society of Anesthesiology Student Essay Award. Acetaminophen is an old drug that is now available in an intravenous formulation. Its advantages and disadvantages are reviewed, including its potential role in multimodal postoperative pain therapy.

A randomised controlled trial of parecoxib, celecoxib and paracetamol as adjuncts to patient-controlled epidural analgesia after caesarean delivery

The benefit of combining non-opioid analgesics with neuraxial opioids for analgesia after caesarean delivery has not been clearly established. Larger doses of paracetamol or cyclooxygenase-2 inhibitors have not been evaluated. A randomised, double blind, double-dummy, parallel group placebo-controlled clinical trial was conducted among women having elective caesarean delivery under spinal anaesthesia, followed by pethidine patient-controlled epidural analgesia. Patients received placebos (group C); intravenous parecoxib 40 mg then oral celecoxib 400 mg at 12 hours (group PC); intravenous paracetamol 2 g then oral 1 g six-hourly (group PA); or these regimens combined (group PCPA). The primary outcome was 24-hour postoperative patient-controlled epidural pethidine use and the main secondary outcome was postoperative pain. One hundred and thirty-eight women were recruited but 27 subsequently met exclusion criteria, leaving 111 who were randomised, allocated and analysed by intention-to-treat (n=23, 30, 32 and 26 in groups C, PC, PA and PCPA respectively). There were no differences between groups for pethidine consumption, based on either intention-to-treat (median 365, 365, 405 and 360 mg in groups C, PC, PA and PCPA respectively, P=0.84) or per protocol analysis (17 major violations). Dynamic pain scores did not differ between groups but requirement for, and dose of, supplementary oral tramadol was least in group PCPA (incidence 23% versus 48%, 70% and 58% in groups C, PC and PA respectively, P=0.004). The addition of regular paracetamol, cyclooxygenase-2 inhibitors or both to pethidine patient-controlled epidural post-caesarean analgesia did not provide a pethidine dose-sparing effect during the first 24 hours.

A Study on Pre-Emptive Analgesic Effect of Intravenous Paracetamol in Functional Endoscopic Sinus Surgeries (FESSs): A Randomized, Double-Blinded Clinical Study

BACKGROUND

Functional Endoscopic Sinus Surgery (FESS) is associated with significant post-operative pain. Intravenous (iv) paracetamol provides pain relief in most patients who have undergone FESS. In some studies, it was found to be inadequate. It has been observed from previous studies conducted on patients undergoing other surgeries like abdominal surgeries that the analgesic efficacy of iv paracetamol improves when used Pre-emptively. There are no studies done previously on use of iv paracetamol Pre-emptively in FESS.

OBJECTIVE

The purpose of the study was to determine the post-operative analgesic effects of Pre-emptive intravenous (iv) paracetamol in FESS.

MATERIALS AND METHODS

Following institutional ethics committee approval, thirty nine American Society of Anesthesiology (ASA) physical status I-II patients were assigned in a randomized manner into two groups: Group I received iv paracetamol 1g, in 100mL, 15 minutes before induction and Group II received iv paracetamol 1g, in 100 mL, at the end of the surgery. The time to first analgesic use and the total analgesic consumed in 24 hours was recorded. Visual Analog Scale (VAS) pain scores were obtained from all patients at 0, 30 minutes, 1, 2, 6, 12 and 24 hours after the end of the Surgery.

RESULTS

Time to first analgesic requirement was significantly longer in Group I compared to Group II (p = 0.0329). Rescue analgesic consumption and post-operative VAS pain scores recorded were significantly lower in Group I compared to Group II (p < 0.05) until 24 after surgery.

CONCLUSION

Pre-emptive iv paracetamol in comparison to intra-operative paracetamol, provided effective and reliable post-operative analgesia after FESS.

Administration of paracetamol versus dipyrone by intravenous patient-controlled analgesia for postoperative pain relief in children after tonsillectomy

BACKGROUND AND OBJECTIVE

We compared the efficacy of intravenous (IV) paracetamol versus dipyrone via patient-controlled analgesia (PCA) for postoperative pain relief in children.

METHODS

The study was composed of 120 children who had undergone elective tonsillectomy after receiving general anesthesia. Patients were divided into 3 groups according to the dosage of postoperative intravenous-patient-controlled analgesia: paracetamol, dipyrone, or placebo. Pain was evaluated using a 0- to 100-mm visual analog scale and 1- to 4-pain relief score at 30 min, 1, 2, 4, 6, 12, and 24h postoperatively. Pethidine (0.25 mg kg(-1)) was administered intravenously to patients requiring rescue analgesia. Pethidine requirements were recorded during the first 24h postoperatively, and treatment related adverse effects were noted.

RESULTS

Postoperative visual analog scale scores were significantly lower with paracetamol group compared with placebo group at 6h (p<0.05), dipyrone group compared with placebo group at 30 min and 6h (p<0.05). No significant differences regarding visual analog scale values at 1, 2, 4, 12, and 24h were found. No significant differences were found between groups with respect to pain relief score (p>0.05). Postoperative pethidine requirements were significantly lower with paracetamol and dipyrone groups compared with placebo group (62.5%, 68.4% vs 90%, p<0.05). No significant differences were found between groups with respect to nausea, vomiting and the any other adverse effects of the drugs (p>0.05).

CONCLUSIONS

Paracetamol and dipyrone have well tolerability profile and effective analgesic properties when administered IV-PCA for postoperative analgesia in children after tonsillectomy.

Pharmacokinetics of paracetamol and its metabolites in women at delivery and post-partum

AIM

A recent report on intravenous (i.v.) paracetamol pharmacokinetics (PK) showed a higher total clearance in women at delivery compared with non-pregnant women. To describe the paracetamol metabolic and elimination routes involved in this increase in clearance, we performed a population PK analysis in women at delivery and post-partum in which the different pathways were considered.

METHODS

Population PK parameters using non-linear mixed effect modelling were estimated in a two-period PK study in women to whom i.v. paracetamol (2 g loading dose followed by 1 g every 6 h up to 24 h) was administered immediately following Caesarean delivery and in a subgroup of the same women to whom single 2 g i.v.loading dose was administered 10-15 weeks post-partum.

RESULTS

Population PK analysis was performed based on 255 plasma and 71 urine samples collected in 39 women at delivery and in eight of these 39 women 12 weeks post-partum. Total clearance was higher in women at delivery compared with 12th post-partum week (21.1 vs. 11.7 l h⁻¹) due to higher clearances to paracetamol glucuronide (11.6 vs. 4.76 l h⁻¹), to oxidative metabolites (4.95 vs. 2.77 l h⁻¹) and of unchanged paracetamol (1.15 vs. 0.75 l h⁻¹). In contrast, there was no difference in clearance to paracetamol sulphate.

CONCLUSION

The increased total paracetamol clearance at delivery is caused by a disproportional increase in glucuronidation clearance and a proportional increase in clearance of unchanged paracetamol and in oxidation clearance, of which the latter may potentially limit further dose increase in this patient group.

Medical management of acute pain in patients with chronic pain

The number of patients with chronic pain has increased over the years, as well as the number of patients who manage chronic pain with opioids. As prescribed opioid use has increased, so has its abuse and misuse. It has also been estimated that the number of people using opioids illicitly has doubled worldwide over the last 20 years. Management of chronic pain with opioids is associated with pathophysiological phenomena such as tolerance, dependence and hyperalgesia. They can become a problem when chronic pain patients present for a surgical procedure. Furthermore, patients who are on opioids on a regular basis require higher amounts during the perioperative period. The perioperative management of the chronic pain patient is difficult and complex. Developing an appropriate plan that can fulfill patients' and surgical team's needs requires skills and experience. The aim of this review is to describe the options available for the optimal perioperative management of acute pain in patients with a history of chronic pain.

The pain management in orthodontics

Pain and discomfort are the frequent side-effects of the orthodontic therapy with fixed appliances. The people who experience orthodontic pain are likely to self-medicate with nonprescription pain relievers before seeing the dentist. It is imperative for an orthodontist to address questions that might arise in a clinical setting from the viewpoint of the clinicians and the patients/parents. This article will provide an overview of the current management strategies which are employed for alleviating orthodontic pain.

Oral vs intravenous paracetamol for lower third molar extractions under general anaesthesia: is oral administration inferior?

BACKGROUND

Paracetamol formulations provide effective analgesia after surgery [Duggan ST, Scott LJ. Intravenous paracetamol (acetominophen). Drugs 2009; 69: 101-13; Toms L, McQuay HJ, Derry S, Moore RA. Single dose oral paracetamol (acetaminophen) for postoperative pain in adults. Cochrane Database Syst Rev 2008: CD004602]. I.V. paracetamol is superior to oral for pain rescue (Jarde O, Boccard E. Parenteral versus oral route increases paracetamol efficacy. Clin Drug Invest 1997; 14: 474-81). By randomized, double-blinded trial, we aimed to determine whether preoperative oral paracetamol provides inferior postoperative analgesia to preoperative i.v. paracetamol.

METHODS

One hundred and thirty participants received either oral paracetamol and i.v. placebo (Group OP), or oral placebo and i.v. paracetamol (Perfalgan™) (Group IP). Oral preparations were given at least 45 min before surgery; i.v. preparations after induction of anaesthesia. Pain was assessed by a 100 mm visual analogue scale (VAS) 1 h from the end of surgery. Rescue analgesia was given on request.

RESULTS

A total of 128 patients completed the study. There were no significant differences in baseline characteristics or intraoperative variables between the groups. The study was designed to reveal whether OP is inferior to IP, with an inferiority margin of 20%. The number of patients reporting satisfactory analgesia at 1 h with VAS ≤ 30 mm were 15 (OP) and 17 (IP), respectively. The secondary outcome measure of the mean (standard deviation) VAS (mm) for the whole of each group was 52 (22) for OP and 47 (22) for IP. Analysis of confidence intervals indicates that oral paracetamol is not inferior to i.v. paracetamol. The median survival (90% CI) to rescue analgesia request was 54.3 (51.2-57.4) min in Group OP and 57.3 (55.4-59.2) min in Group IP; there was no significant difference in this measure.

CONCLUSIONS

In this study of lower third molar extraction, oral paracetamol is not inferior to i.v. for postoperative analgesia. ISRCTN Registration http://www.controlled-trials.com/ISRCTN77607163.