Plasma concentrations following repeated rectal or intravenous administration of paracetamol after heart surgery

Intravenous acetaminophen for postoperative pain control after open abdominal and thoracic surgery in pediatric patients: a systematic review and meta-analysis

Pediatric opioid exposure increases short- and long-term adverse events (AE). The addition of intravenous acetaminophen (IVA) to pediatric pain regimes to may reduce opioids but is not well studied postoperatively. Our objective was to quantify the impact of IVA on postoperative pain, opioid use, and AEs in pediatric patients after major abdominal and thoracic surgery. Medline, Embase, CINAHL, Web of Science, and Cochrane Library were searched systematically for randomized controlled trials (RCTs) comparing IVA to other modalities. Five RCTs enrolling 443 patients with an average age of 2.12 years (± 2.81) were included. Trials comparing IVA with opioids to opioids alone were meta-analyzed. Low to very low-quality evidence demonstrated equivalent pain scores between the groups (-0.23, 95% CI -0.88 to 0.40, p 0.47) and a reduction in opioid consumption (-1.95 morphine equivalents/kg/48 h, 95% CI -3.95 to 0.05, p 0.06) and minor AEs (relative risk 0.39, 95% CI 0.11 to 1.43, p 0.15). We conclude that the addition of IVA to opioid-based regimes in pediatric patients may reduce opioid use and minor AEs without increasing postoperative pain. Given the certainty of evidence, further research featuring patient-important outcomes and prolonged follow-up is necessary to confirm these findings.

Systematic Review of Systemic and Neuraxial Effects of Acetaminophen in Preclinical Models of Nociceptive Processing

Acetaminophen (APAP) in humans has robust effects with a high therapeutic index in altering postoperative and inflammatory pain states in clinical and experimental pain paradigms with no known abuse potential. This review considers the literature reflecting the preclinical actions of acetaminophen in a variety of pain models. Significant observations arising from this review are as follows: 1) acetaminophen has little effect upon acute nociceptive thresholds; 2) acetaminophen robustly reduces facilitated states as generated by mechanical and thermal hyperalgesic end points in mouse and rat models of carrageenan and complete Freund’s adjuvant evoked inflammation; 3) an antihyperalgesic effect is observed in models of facilitated processing with minimal inflammation (eg, phase II intraplantar formalin); and 4) potent anti-hyperpathic effects on the thermal hyperalgesia, mechanical and cold allodynia, allodynic thresholds in rat and mouse models of polyneuropathy and mononeuropathies and bone cancer pain. These results reflect a surprisingly robust drug effect upon a variety of facilitated states that clearly translate into a wide range of efficacy in preclinical models and to important end points in human therapy. The specific systems upon which acetaminophen may act based on targeted delivery suggest both a spinal and a supraspinal action. Review of current targets for this molecule excludes a role of cyclooxygenase inhibitor but includes effects that may be mediated through metabolites acting on the TRPV1 channel, or by effect upon cannabinoid and serotonin signaling. These findings suggest that the mode of action of acetaminophen, a drug with a long therapeutic history of utilization, has surprisingly robust effects on a variety of pain states in clinical patients and in preclinical models with a good therapeutic index, but in spite of its extensive use, its mechanisms of action are yet poorly understood.

Nonopioid Analgesics in Postoperative Pain Management After Cardiac Surgery

Opioid analgesia is still considered the standard of practice for cardiac surgery. In recent years, combinations of several nonnarcotic analgesics and regional analgesia have shown promise in restricting opioid use during and after cardiac surgery. Ketamine infusion, dexmedetomidine infusion, acetaminophen, ketorolac, and gabapentin are useful adjuvants in cardiac anesthesia practice and have opioid-sparing properties. The beneficial effects of nonnarcotic multimodal analgesia on intraoperative stress response, recovery profile, postoperative pain, and persistent opioid use after cardiac surgery are yet to be established, and further randomized clinical trials are required.

Enhanced recovery after cardiac surgery program to improve patient outcomes

This article details the obstacles of implementing a cardiac-specific enhanced recovery after surgery (ERAS) program in a 919-bed not-for-profit community-based health system and the benefits of ERAS programs for different patient populations.

Assessment and Early Management of Pain in Hip Fractures: The Impact of Paracetamol

Introduction

As the number of patients sustaining hip fractures increases, interventions aimed at improving patient comfort and reducing complication burden acquire increased importance. Frailty, cognitive impairment, and difficulty in assessing pain control characterize this population. In order to inform future care, a review of pain assessment and the use of preoperative intravenous paracetamol (IVP) is presented.

Materials and Methods

Systematic review of preoperative IVP administration in patients presenting with a hip fracture.

Results

Intravenous paracetamol is effective in the early management of pain control in the hip fracture population. There is a considerable decrease in use of breakthrough pain medications when compared with other pain relief modalities. Additionally, IVP reduces the incidence of opioid-induced complications, reduces length of stay, and lowers mean pain scores. Another significant finding of this study is the poor administration of all analgesics to patients with hip fracture with up to 72% receiving no prehospital analgesia.

Discussion

The potential benefits of IVP as routine in the early management of hip fracture-related pain are clear. Studies of direct comparison between analgesia regimes to inform optimum bundles of analgesic care are sparse. This study highlights the need for properly constructed pathway-driven comparator studies of contemporary analgesia regimes, with IVP as a central feature to optimize pain control and minimize analgesia-related morbidity in this vulnerable population.

Comparison of tramadol/acetaminophen fixed-dose combination, tramadol, and acetaminophen in patients undergoing ambulatory arthroscopic meniscectomy

OBJECTIVES

Preemptive analgesia is a technique in which analgesics are administered before a surgery to provide better postoperative pain relief with fewer side effects. In this study, we aimed to compare the preemptive efficacy of tramadol/acetaminophen fixed-dose combination, tramadol, and acetaminophen in patients undergoing ambulatory arthroscopic partial meniscectomy.

METHODS

We evaluated the patient records of 75 patients who underwent ambulatory arthroscopic partial meniscectomy. We divided the patients into three groups consisting of 20 patients each to equalize the groups. Group A comprised patients who were administered 37.5 mg tramadol/325 mg acetaminophen fixed-dose combination, Group B comprised patients who were administered 50 mg tramadol, and Group C comprised patients who were administered 500 mg acetaminophen. Premedication was not used in any group.

RESULTS

There were no significant differences between the groups in terms of age, sex, BMI, and duration of surgery and anesthesia. All patients in Group B and Group C and 17 patients in Group A required rescue analgesics in the first 6 h. Visual analog scale (VAS) was 4.75 ± 3.05 in Group B at time 0 and was 6.10 ± 1.86 in Group C in the first hour and was higher than the other groups with a statistically significance (p = 0.030 and 0.020, respectively). VAS at 24 h postoperatively was ≤3 (1.60 ± 1.63, 1.55 ± 1.84 and 1.70 ± 0.65 respectively in each group), and none of the patients in any group required rescue analgesics. No major side effects, except for slight nausea in one patient requiring no medication, were noted in any group.

CONCLUSION

The fixed-dose combination of tramadol/acetaminophen or tramadol alone is better than acetaminophen alone as a preemptive analgesic in patients undergoing ambulatory arthroscopic meniscectomy.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Effects of metamizole, MAA, and paracetamol on proliferation, apoptosis, and necrosis in the pancreatic cancer cell lines PaTu 8988 t and Panc-1

BACKGROUND

Adenocarcinoma of the pancreas is one of the most aggressive cancer diseases affecting the human body. Recent research has shown the importance of the perioperative phase in disease progression. Particularly during this vulnerable phase, substances such as metamizole and paracetamol are given as general anesthetics and postoperative analgesics. Therefore, the effects of metamizole and paracetamol on tumor progression should be investigated in more detail because the extent to which these substances influence the carcinogenesis of pancreatic carcinoma is still unclear. This study analyzed the influence of metamizole and its active metabolites MAA (4-N-methyl-aminoantipyrine) and paracetamol on the proliferation, apoptosis, and necrosis of the pancreatic cancer cell lines PaTu 8988t and Panc-1 in vitro.

METHODS

Cell proliferation was measured by means of the ELISA BrdU assay and the rate of apoptosis by flow cytometry using the Annexin V assay.

RESULTS

Metamizole and paracetamol significantly inhibited cell proliferation in pancreatic cancer cells. After the addition of metamizole to PaTu 8988t cells, the rate of apoptosis was reduced after 3 h of incubation but significantly increased after 9 h of incubation.

CONCLUSION

The oncogenic potential of pancreatic adenocarcinoma is mainly characterized by its extreme growth rate. Non-opioid analgesics such as metamizole and paracetamol are given as general anesthetics and postoperative analgesics. The combination of metamizole or paracetamol with cytotoxic therapeutic approaches may achieve synergistic effects. Further studies are necessary to identify the underlying mechanisms so that new therapeutic options may be developed for the treatment of this aggressive tumor.

Perioperative management in children with chronic pain

Children with chronic pain often undergo surgery and effective perioperative management of their pain can be challenging. Identification of the pediatric chronic pain patient preoperatively and development of a perioperative pain plan may help ensure a safer and more comfortable perioperative course. Successful management usually requires multiple different classes of analgesics, regional anesthesia, and adjunctive nonpharmacological therapies. Neuropathic and oncological pain can be especially difficult to treat and usually requires an individualized approach.

Acetaminophen, nonsteroidal anti-inflammatory drugs, and cyclooxygenase-2 selective inhibitors: an update

SUMMARY

Plastic and cosmetic surgery is often performed as an ambulatory procedure, and pain is often mild to moderate. Good pain relief is central to patient comfort and satisfaction. Analgesics used should ensure rapid onset and adequate pain relief lasting a sufficiently long duration with minimal or no side effects. Acetaminophen is well tolerated by patients, efficacious, and associated with only minor side effects, when used in the minimal effective doses. Nonsteroidal anti-inflammatory drugs (NSAIDs) are more efficacious, having lower numbers needed to treat compared with acetaminophen, but have several side effects and contraindications. However, when used in the correct doses in healthy patients, NSAIDs are excellent for pain management with one caveat that there is an increased risk for oozing or bleeding. In contrast, cyclooxygenase inhibitors (Coxibs) are equally efficacious as NSAIDs but have the added advantage that they have minimal or no effect on platelet function, and therefore, the risk for bleeding complications is minimal. However, there has been some concern about the risk of vascular events in patients with ischemic heart disease, specifically when using Coxibs, but even some NSAIDs, for example, diclofenac. In conclusion, acetaminophen should be given postoperatively to all patients undergoing plastic surgical procedures. For patients undergoing moderately invasive surgery, the addition of Coxibs to acetaminophen would be an advantage except in the patient with ischemic heart disease where NSAIDs could have a place in management of pain. Side effects and contraindications of NSAIDs, however, restrict their use to the healthy patient with mild comorbidities.

Pediatric ambulatory anesthesia

Pediatric patients often undergo anesthesia for ambulatory procedures. This article discusses several common preoperative dilemmas, including whether to postpone anesthesia when a child has an upper respiratory infection, whether to test young women for pregnancy, which children require overnight admission for apnea monitoring, and the effectiveness of nonpharmacological techniques for reducing anxiety. Medication issues covered include the risks of anesthetic agents in children with undiagnosed weakness, the use of remifentanil for tracheal intubation, and perioperative dosing of rectal acetaminophen. The relative merits of caudal and dorsal penile nerve block for pain after circumcision are also discussed.

The pharmacokinetic profile of intravenous paracetamol in adult patients undergoing major abdominal surgery

BACKGROUND

Intravenous (IV) paracetamol is commonly used in the postoperative period for the treatment of mild to moderate pain. The main pathways for paracetamol metabolism are glucuronidation, sulfation, and oxidation, accounting for approximately 55%, 30%, and 10% of urinary metabolites, respectively. The aim of this study was to describe the pharmacokinetics of IV paracetamol and its metabolites in adult patients after major abdominal surgery.

METHODS

Twenty patients were given 1 g of paracetamol by IV infusion at induction of anesthesia (Interval 1) and every 6 hours thereafter, with the final dose given at 48-72 hours (Interval 2). Plasma and urine samples were collected for up to 8 hours after infusion for both intervals. The samples were analyzed by high-performance liquid chromatography to determine the amount of paracetamol and its metabolites. The data were modeled in Phoenix WinNonlin using a user-defined ASCII parent-metabolite model with linear disposition, to obtain the estimates for volume of distribution, metabolic and urinary clearance.

RESULTS

Mean (95% confidence interval) metabolic clearance to paracetamol glucuronide increased from 0.06 (0.05-0.08) to 0.14 (0.11-0.18) L · h⁻¹ · kg⁻¹, P value <0.001 and urinary clearance increased from 0.08 (0.07-0.09) to 0.14 (0.10-0.17) L · h⁻¹ · kg⁻¹, P value 0.002. The mean (95% confidence interval) volume of distribution of paracetamol increased from 0.17 (0.12-0.21) to 0.43 (0.27-0.59) L · kg⁻¹, P value 0.032.

CONCLUSIONS

After major abdominal surgery, there were apparent increases in the metabolic conversion to paracetamol glucuronide and its urinary clearance suggesting potential induction of paracetamol glucuronidation.

Can intravenous paracetamol reduce opioid use in preoperative hip fracture patients?

Pain due to intra- and extracapsular hip fractures is usually treated with opioid medication. Paracetamol (acetaminophen in North America) has better bioavailability when given intravenously than orally and has been successfully used in the postoperative care of orthopedic patients. However, no study has evaluated its use in the preoperative trauma patient. Our unit conducted a prospective, consecutive cohort study to investigate the opioid-sparing effect of regularly administered intravenous paracetamol compared with oral paracetamol in preoperative hip fracture patients. The total opioid dose given, based on conversion to intravenous morphine, and the reported pain score were evaluated in 75 patients. There were 28 patients in the control group who were give routine oral paracetamol and oral opioids, with morphine for breakthrough pain. There were 47 patients in the study group who received only routine intravenous paracetamol, with opioids reserved for breakthrough pain. The patients in the 2 groups had similar characteristics. The mean preoperative oral paracetamol dose for the control group was 7.2 g compared with 6.3 g in the study group. There was a significant reduction (P<.005) in the mean total intravenous morphine with intravenous paracetamol (6.5 mg) compared with oral paracetamol (21.8 mg). There was no difference in the mean pain score between the groups, 2.1 vs 1.8 (P=.3). Intravenous paracetamol had a significant opioid-sparing effect and satisfactory pain relief in preoperative hip fracture patients.

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.

Acute pain management in the postanesthesia care unit

Pain management in the postanesthesia care unit (PACU) is continually evolving, with several new nonopioids expanding the list of available agents. Pain in the PACU is not an inevitable outcome of surgery. With careful planning, multimodal analgesic techniques instituted preoperatively will reduce pain in the PACU. Accurate assessment of the characteristics of pain will direct rational drug choices while minimizing side effects. Better management of pain in the PACU setting will likely improve patient satisfaction and facilitate shorter PACU stays.

Clinical and economic evidence for intravenous acetaminophen

Intravenous acetaminophen received United States Food and Drug Administration approval in November 2010 for the management of mild-to-moderate pain, management of moderate-to-severe pain with adjunctive opioid analgesics, and reduction of fever. Although intravenous acetaminophen generally improved pain relief and demonstrated opioid-sparing effects compared with placebo, it did not consistently reduce the frequency of opioid-related adverse events (e.g., postoperative nausea and vomiting). The safety and efficacy of intravenous acetaminophen as an antipyretic agent have been documented in adults and children; however, its cost is several-fold higher than that of the oral and rectal formulations. Although use of intravenous acetaminophen has reduced other postoperative resource utilization (e.g., hospital length of stay) in some studies outside the United States in patients undergoing abdominal surgery, a full economic evaluation in the United States has yet to be undertaken. In addition, its administration time (15-min infusion) and packaging (glass, single-use vial) have the potential to adversely affect patient flow in the postanesthesia care unit, create burden on patient care units, and lead to drug waste. Furthermore, 1 g of intravenous acetaminophen is formulated in 100 ml of solution, which may be an issue for patients with fluid restrictions. Given the clinical and economic evidence currently available, intravenous acetaminophen should not replace oral or rectal acetaminophen, but its use may be considered in a limited number of patients who cannot receive drugs orally and rectally and who cannot tolerate other parenteral nonopioid analgesic or antipyretic agents.

Intravenous paracetamol toxicity in a malnourished child

We present a case of intravenous (IV) paracetamol overdose in a nutritionally malnourished child during hospital admission. A ten-fold IV paracetamol dosing error ocurred, with delayed recognition and treatment resulting in transient hepatotoxicity, with a peak alanine transaminase (ALT) of 1378 IU/L in a 3-year-old child. Our case suggests that hepatotoxicity may occur for lower doses of IV paracetamol compared to oral ingestion, especially in the malnourished, and that a dose less than 150 mg/kg of IV paracetamol should be used to define treatment following overdose in a child with potential nutritional deficiencies.

Acetaminophen injection: a review of clinical information

Acetaminophen injection is an antipyretic and analgesic agent recently marketed in the United States as Ofirmev. Five published trials directly compare acetaminophen injection to drugs available in the United States. For management of pain in adults, acetaminophen injection was at least as effective as morphine injection in renal colic, oral ibuprofen after cesarean delivery, and oral acetaminophen after coronary artery bypass surgery. In children (3 to 16 years old), single-dose acetaminophen injection was similar to meperidine intramuscular (i.m.) for pain after tonsillectomy; readiness for discharge from the recovery room was shorter with acetaminophen injection (median 15 minutes) compared with meperidine i.m. (median 25 minutes), P = .005. In children (2 to 5 years old) postoperative adenotonsillectomy or adenoidectomy, the time to rescue analgesia was superior with high-dose acetaminophen rectal suppository (median 10 hours) compared with acetaminophen injection (median 7 hours), P = .01. One published trial demonstrated acetaminophen injection is noninferior to propacetamol injection for fever related to infection in pediatric patients. Dosing adjustments are not required when switching between oral and injectable acetaminophen formulations in adult and adolescent patients. Acetaminophen injection represents another agent for multimodal pain management.

Acetaminophen Intravenous

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. Subscribers to The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X.). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The April 2011 monograph topics are on vilazodone hydrochloride, hydroxyprogesterone caproate, gabapentin extended-release, spinosad 0.9% topical suspension, and aclidinium bromide. The DUE/MUE is on pegloticase.

Intravenous acetaminophen

Acetaminophen has unique analgesic and antipyretic properties. It is globally recommended as a first-line agent for the treatment of fever and pain due to its few contraindications. Acetaminophen lacks the significant gastrointestinal and cardiovascular side effects associated with nonsteroidal anti-inflammatory drugs and narcotics. An intravenous formulation of acetaminophen is available in Europe and is currently undergoing extensive clinical development for use in the United States. This use may have important implications for management of postoperative pain and fever. This review summarizes recent clinical trial experiences with intravenous acetaminophen for the treatment of postoperative pain and fever in adult and pediatric subjects.

Paracetamol for intravenous use in medium--and intensive care patients: pharmacokinetics and tolerance

PURPOSE

We studied the pharmacokinetics of paracetamol and determine the incidence of hypotension after intravenous administration in medium- (MCU) and intensive care (ICU) patients.

METHODS

All patients on the ICU/MCU starting with paracetamol i.v. were included, yielding 38 patients. Blood samples were collected at predetermined time points to determine paracetamol serum concentration. The number of patients with a clinically relevant reduction in systolic blood pressure (SBP) and the number of patients that needed intervention to regain an acceptable blood pressure level were assessed.

RESULTS

Overall, pharmacokinetic data were roughly comparable with earlier publications, but differences were noted in the subgroup ICU patients. Also, there was a trend to a larger peak serum concentration (p = 0.052) and a significantly smaller volume of distribution (p = 0.033) in MCU patients compared with ICU patients. Twenty-two percent (22%) and 33% of patients had a clinically relevant reduction in systolic blood pressure (SBP) 15 and 30 min after start of paracetamol infusion, respectively. In six patients (16%), an intervention was needed to correct blood pressure. Overall, SBP was significantly reduced at T = 15 min and 30 min postinfusion (p < 0.003 at both time points) when compared with SBP at the start of paracetamol infusion.

CONCLUSIONS

Further research on differences in paracetamol pharmacokinetics between ICU and MCU patients is warranted, as these differences might result in differences in efficacy. Furthermore, administration of paracetamol i.v. as potential cause of hypotension in the critically ill patient must not be overlooked.

Intravenous paracetamol (acetaminophen)

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

Peri-operative use of paracetamol

This article is a review of the peri-operative use of paracetamol. It reviews the pharmacology of paracetamol, highlighting new information about the mechanism of action, and examines its therapeutic use in the peri-operative period, focusing on efficacy, route of administration, and the use of a loading dose to improve early postoperative analgesia.

Recent advances in the pharmacological management of pain

Pain is an unpleasant sensation that originates from ongoing or impending tissue damage. Management of different types of pain (acute, postoperative, inflammatory, neuropathic or cancer) is the most frequent issue encountered by clinicians and pharmacological therapy is the first line of approach for the treatment of pain. This review presents and discusses recent clinical advances regarding both the improvements in delivery of analgesic drugs and improvements in the design of analgesic molecules. The new modalities of administration of analgesics used in the clinic are reviewed, including skin patches, oral and mucosal sprays, transdermal delivery systems and intranasal administration. New insights are then presented on standard drugs used to relieve pain, such as opioids (including tramadol), NSAIDs including selective cyclo-oxygenase-2 inhibitors, paracetamol (acetaminophen), local anaesthetics and adjuvant analgesics such as antidepressants, anticonvulsants (gabapentin and pregabalin), cannabinoids, ketamine and others (e.g. nefopam). Although the understanding of pain mechanisms has improved significantly recently, much more is yet to be discovered and awaited. Broadening of our knowledge is needed to improve basic and clinical research in this field in order to better alleviate pain in millions of people.

Intravenous paracetamol as adjunctive treatment for postoperative pain after cardiac surgery: a double blind randomized controlled trial

BACKGROUND

Nonsteroidal anti-inflammatory drugs and opioids are routinely used after cardiac surgery in order to mitigate postoperative pain; however, these drugs are burdened by side effects. Tramadol and paracetamol are believed to be lacking in such side effects. The aim of this study was to examine the efficacy of intravenous paracetamol as an adjunctive analgesic to a tramadol-based background analgesia after cardiac surgery.

METHODS

A total of 113 patients participated in this single center, placebo-controlled, double-blind, randomized trial. Fifty-six patients were randomized to receive paracetamol and 57 to placebo. Intravenous study drug (1 g) was administered 15 min before the end of surgery and every 6h for 72 h. Standard analgesia (tramadol) and anti-emetic prophylactic regimen (ondansetron) were available to both patient groups. Postoperative pain was evaluated by visual analog scale, and it was measured at rest and during a deep breath. A rescue dose of 2-5 mg of intravenous morphine was administered whenever the VAS score was greater than 3.

RESULTS

Baseline characteristics were equivalent between the two groups. At 12, 18, 24 h after the end of operation, patients who received paracetamol had significantly less pain at rest (p=0.0041, 0.0039, 0.0044, respectively); after this time the two groups did not differ. During a deep breath the difference was significant only at 12 h (p=0.0040). Paracetamol group required less cumulative morphine than placebo group (48 mg vs 97 mg) even if the difference did not reach statistical significance (p=0.274).

CONCLUSIONS

In patients undergoing cardiac surgery, intravenous paracetamol in combination with tramadol provides effective pain control.