Intravenous paracetamol (acetaminophen)

A comparative study of intravenous paracetamol and intravenous tramadol for postoperative analgesia in laparotomies

Background:

Pain in the perioperative setting or thereafter plays a significant role in delaying an otherwise successful recovery. Hence, mitigation of such postoperative pain assumes importance. Among the various agents employed for such mitigation, opioids and non-steroidal anti-inflammatory drugs have for some time taken center stage. However, alas they are not without their share of adverse effects. This study was undertaken with the purpose of elucidating the efficacy of intravenous (IV) paracetamol as compared to IV tramadol in mitigating postoperative pain while observing its effect on hemodynamic stability and the presence of adverse drug reactions, if any.

Materials and Methods:

A total of 60 randomized cases aged ranges from 20 to 60 years of both sexes divided into two groups (each for paracetamol and tramadol) scheduled for laparotomies were administered IV paracetamol and tramadol for postoperative pain relief and assessed with visual analog scale (VAS) score and variations in vital parameters to ascertain extent of pain relief and post-operative nausea vomiting (PONV).

Results:

Data so collected was statistically interpreted, and observations extrapolated. Save for a perceptible decline in PONV with paracetamol group compared with tramadol group with a statistically significant P < 0.001, nothing statistically significant was observed in any other parameter, including VAS scores between either group.

Conclusion:

IV paracetamol is a safer alternative to tramadol with lesser PONV in the postoperative period translates into the lesser duration of hospitalization and hence earlier discharge.

Clinical pharmacology of paracetamol in neonates: a review

Paracetamol is commonly used to control mild-to-moderate pain or to reduce opioid exposure as part of multimodal analgesia, and is the only compound recommended to treat fever in neonates. Paracetamol clearance is lower in neonates than in children and adults. After metabolic conversion, paracetamol is subsequently eliminated by the renal route. The main metabolic conversions are conjugation with glucuronic acid and with sulphate. In the urine of neonates sulphated paracetamol concentration is higher than the glucuronidated paracetamol level, suggesting that sulfation prevails over glucuronidation in neonates. A loading dose of 20 mg/kg followed by 10 mg/kg every 6 hours of intravenous paracetamol is suggested to achieve a compartment concentration of 11 mg/L in late preterm and term neonates. Aiming for the same target concentration, oral doses are similar with rectal administration of 25 to 30 mg/kg/d in preterm neonates of 30 weeks' gestation, 45 mg/kg/d in preterm infants of 34 weeks' gestation, and 60 mg/kg/d in term neonates are suggested. The above-mentioned paracetamol doses for these indications (pain, fever) are well tolerated in neonates, but do not result in a significant increase in liver enzymes, and do not affect blood pressure and have limited effects on heart rate. In contrast, the higher doses suggested in extreme preterm neonates to induce closure of the patent ductus arteriosus have not yet been sufficiently evaluated regarding efficacy or safety. Moreover, focussed pharmacovigilance to explore the potential causal association between paracetamol exposure during perinatal life and infancy and subsequent atopy is warranted.

Intravenous versus Oral Acetaminophen for Pain: Systematic Review of Current Evidence to Support Clinical Decision-Making

BACKGROUND

Intravenous (IV) acetaminophen is increasingly used around the world for pain control for a variety of indications. However, it is unclear whether IV administration offers advantages over oral administration.

OBJECTIVE

To identify, summarize, and critically evaluate the literature comparing analgesic efficacy, safety, and pharmacokinetics for IV and oral dosage forms of acetaminophen.

DATA SOURCES

A literature search of the PubMed, Embase, and International Pharmaceutical Abstracts databases was supplemented with keyword searches of Science Direct, Wiley Library Online, and Springer Link databases for the period 1948 to November 2014. The reference lists of identified studies were searched manually.

STUDY SELECTION AND DATA EXTRACTION

Randomized controlled trials comparing IV and oral dosage forms of acetaminophen were included if they assessed an efficacy, safety, or pharmacokinetic outcome. For each study, 2 investigators independently extracted data (study design, population, interventions, follow-up, efficacy outcomes, safety outcomes, pharmacokinetic outcomes, and any other pertinent information) and completed risk-of-bias assessments.

DATA SYNTHESIS

Six randomized clinical trials were included. Three of the studies reported outcomes pertaining to efficacy, 4 to safety, and 4 to pharmacokinetics. No clinically significant differences in efficacy were found between the 2 dosage forms. Safety outcomes were not reported consistently enough to allow adequate assessment. No evidence was found to suggest that increased bioavailability of the IV formulation enhances efficacy outcomes. For studies reporting clinical outcomes, the results of risk-of-bias assessments were largely unclear.

CONCLUSIONS

For patients who can take an oral dosage form, no clear indication exists for preferential prescribing of IV acetaminophen. Decision-making must take into account the known adverse effects of each dosage form and other considerations such as convenience and cost. Future studies should assess multiple-dose regimens over longer periods for patients with common pain indications such as cancer, trauma, and surgery.

Single crystal XRD, vibrational and quantum chemical calculation of pharmaceutical drug paracetamol: A new synthesis form

The common house hold pharmaceutical drug, paracetamol (PAR), has been synthesized from 4-chloroaniline as a first ever report. After the synthesis, good quality single crystals were obtained for slow evaporation technique under the room temperature. The crystal and molecular structures were re-determined by the single crystal X-ray diffraction. The vibrational spectral measurements were carried out using FT-IR and FT-Raman spectroscopy in the range of 4000-400 cm(-1). The single crystal X-ray studies shows that the drug crystallized in the monoclinic system polymorph (Form-I). The crystal packing is dominated by N-H⋯O and O-H⋯O classical hydrogen bonds. The ac diagonal of the unit cell features two chain C(7) and C(9) motifs running in the opposite directions. These two chain motifs are cross-linked to each other to form a ring R4(4)(22) motif and a chain C2(2)(6) motif which is running along the a-axis of the unit cell. Along with the classical hydrogen bonds, the methyl group forms a weak C-H⋯O interactions in the crystal packing. It offers the support for molecular assembly especially in the hydrophilic regions. Further, the strength of the hydrogen bonds are studied the shifting of vibrational bands. Geometrical optimizations of the drug molecule were done by the Density Functional Theory (DFT) using the B3LYP function and Hartree-Fock (HF) level with 6-311++G(d,p) basis set. The optimized molecular geometry and computed vibrational spectra are compared with experimental results which show significant agreement. The factor group analysis of the molecule was carried out by the various molecular symmetry, site and factor group species using the standard correlation method. The Natural Bond Orbital (NBO) analysis was carried out to interpret hyperconjugative interaction and intramolecular charge transfer (ICT). The chemical softness, chemical hardness, electro-negativity, chemical potential and electrophilicity index of the molecule were found out first time by HOMO-LUMO plot. The frontier orbitals shows lower band gap values signify the possible biological/pharmaceutical activity of the molecule. The thermodynamical properties are also obtained from the calculated frequencies of the optimized structures.

Editor's Choice-Chest pain relief in patients with acute myocardial infarction

Chest pain is the prevalent symptom at presentation in patients with acute myocardial infarction (AMI). Despite the complete absence of rigorous studies designed to assess the impact of morphine administration in patients with AMI, clinical practice guidelines strongly recommend morphine for analgesia. However, when using morphine to relieve chest pain in AMI patients, physicians must be aware that hypotension, respiratory depression, vomiting, and delayed onset of action of antiplatelet agents are potential unwanted side effects of the drug. The purpose of this report is to review morphine's clinical and side effects and to propose strategies able to reduce chest pain in AMI patients.

Clinical evaluation of intravenous paracetamol versus Parecoxib for postoperative analgesia after general anaesthesia

BACKGROUND

Postoperative pain has a significant impact on patient's recovery and optimal nonopioid analgesia would reduce postoperative pain and pain-related complications. This study was aimed to evaluate the analgesic efficacy and safety of intravenous paracetamol versus parecoxib for postoperative analgesia after surgery.

MATERIALS AND METHODS

Sixty-eight adult consented patients belonging to ASA I and II, scheduled for surgery, were randomly allocated in two treatment groups receiving either infusion of paracetamol (1 gm) or parecoxib (40 mg). The surgical and anesthetic techniques were standardized. Postoperative pain was assessed using visual analog score (VAS) at rest, during coughing and movement. The primary variables were the differences between the mean values of postoperative pain scores, time of first dose of rescue analgesic (tramadol) required, and patient satisfaction throughout the first 12 postoperatively.

RESULTS

There was no significant difference among groups to first request for tramadol. The VAS score was significantly less in parecoxib group at rest compared to paracetamol group (P<0.05), but the same did not differ for pain score while coughing and movement. Patients in the parecoxib group were more satisfied regarding the postoperative pain management at 12 h postoperatively. The incidence of adverse side effects was infrequent in both the groups.

CONCLUSION

Postoperative nonopioid intravenous analgesia with paracetamol and parecoxib is comparable in the early postoperative period with no adverse effects.

Perioperative analgesic effects of intravenous paracetamol: Preemptive versus preventive analgesia in elective cesarean section

Background:

Cesarean section (CS) is the one of the most common surgical procedure in women. There is preoperative stress effect before the delivery of the baby as (intubation and skin incision). There is acute postoperative pain, which may be progressed to chronic pain. All these perioperative stress effects need for various approach of treatment, which including systemic and neuraxial analgesia. The different analgesia modalities may affect and impair early interaction between mother and infant. Preemptive intravenous (I.V.) paracetamol (before induction) may reduce stress response before the delivery of the baby, intraoperative opioids and postoperative pain.

Objectives:

The aim of this study to compare between the administration of I.V. paracetamol as: Preemptive analgesia (preoperative) and preventive analgesia (at the end of surgery) as regards of hemodynamic, pain control, duration of analgesia, cumulative doses of intraoperative opioids and their related side-effects and to compare between two different protocols of postoperative analgesia and their cumulative doses.

Patients and Methods:

Sixty patients undergoing elective CS were randomly enrolled in this study and divided into two groups of 30 patients each. Group I: i.V. paracetamol 1 g (100 ml) was given 30 min before induction of anesthesia. Group II: i.V. paracetamol 1 g (100 ml) was given 30 min before the end of surgery. Heart rate, systolic blood pressure, diastolic blood pressure, and peripheral oxygen saturation were recorded. Postoperative pain was assessed by visual analog score. Postoperative pethidine was given by two different protocols: group I: 0.5 mg/kg was divided into 0.25 mg/kg intramuscular and 0.25 mg/kg I.V. Group II was given pethidine 0.5 mg/kg I.V. Doses of intraoperative fentanyl, postoperative pethidine, duration of paracetamol analgesic time, time to next analgesia, and side-effects of opioid were noted and compared.

Result:

Preemptive group had hemodynamic stability, especially before delivery of the baby P < 0.001. Preventive group had longer duration of paracetamol analgesia and higher intraoperative opioid P < 0.001 and P < 0.01, respectively. Preemptive group had longer time for next analgesia and lower incidences of postoperative side-effects P < 0.001 and P < 0.05. Preemptive group had higher pain scores in immediate postoperative and after 6 h but preventive group had higher pain scores in 4 and 8 h postoperatively P < 0.001 and P < 0.01, respectively.

Conclusion:

Preemptive paracetamol and immediate postoperative opioid analgesia were more effective than preventive paracetamol.

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.

Intravenous acetaminophen in bariatric surgery: effects on opioid requirements

BACKGROUND

Opioids are commonly used after bariatric surgery for pain control because of their potent analgesic effects. Nevertheless, the morbidly obese patient has increased risk for developing adverse effects produced by opioids (such as sedation, apnea, hypoxemia, ileus, and vomiting). Intravenous acetaminophen (IVA) has been evaluated in some specialties showing a reduction in opioid consumption. The purpose of this study was to evaluate the effect on opioid consumption when IVA is administered in bariatric surgery patients.

MATERIAL AND METHODS

A retrospective study was performed in patients who underwent bariatric surgery. Group A included those patients who received IVA perioperatively and group B those who did not. The amount of opioids administered was calculated and compared for each group.

RESULTS

Group A included 38 cases (44.7%) and group B included 47 cases (55.3%). A comparison was performed in terms of age (P = 0.349), body mass index (P = 0.311), gender (P = 0.890), American Society of Anesthesiologist score (P = 0.438), total surgical time (P = 0.497), perioperative complications (P = 0.786), number of procedures per surgeon (P = 0.08), and type of surgical procedure (P ≤ 0.01). Group A had a mean 24-h total opioid dose of 99.5 mg, whereas group B of 164.6 mg (P = 0.018). Group A received 39.5% less opioids than group B. A post hoc analysis determined a statistical power of 0.74.

CONCLUSIONS

IVA used perioperatively can decrease opioid consumption in patients after bariatric surgery. Randomized trials are needed to corroborate these results.

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.

The effect of preoperative intravenous paracetamol administration on postoperative fever in pediatrics cardiac surgery

Background:

Post-operative fever is a common complication of cardiac operations, which is known to be correlated with a greater degree of cognitive dysfunction 6 weeks after cardiac surgery. The aim of the present study was to examine efficacy and safety of single dose intravenous Paracetamol in treatment of post-operative fever in children undergoing cardiac surgery.

Materials and Methods:

In this randomised, double-blind, placebo-controlled clinical trial, 80 children, aged 1-12 years, presenting for open heart surgery were entered in the trial and randomly allocated into two groups: Placebo and Paracetamol. After induction of anaesthesia, 15 mg/kg intravenous Paracetamol solution was infused during 1 h in the Paracetamol group. Patients in placebo group received 15 mg/kg normal saline infusion during the same time. Since the end of operation until next 24 h in intensive care unit, axillary temperature of the two group patients was recorded in 4-h intervals. Any fever that occurred during this period had been treated with Paracetamol suppository (125 mg) and the amount of antipyretic drug consumption for each patient had been recorded. In order to examine the safety of Paracetamol, patients were evaluated for drug complication at the same time.

Results:

Mean axillary temperature during first 24 h after operation was significantly lower in Paracetamol group compared with placebo group (P = 0.001). Overall fever incidence during 24 h after operation was higher in placebo group compared with Paracetamol group (P = 0.012). Of Paracetamol group patients, 42.5% compared with 15% of placebo group participants had no consumption of antipyretic agent (Paracetamol suppository) during 24 h after operation (P = 0.001).

Conclusion:

This study suggests that single dose administration of intravenous Paracetamol before paediatric cardiac surgeries using cardiopulmonary bypass; reduce mean body temperature in the first 24 h after operation.

Intravenous paracetamol for fever control in acute brain injury patients: cerebral and hemodynamic effects

BACKGROUND

Fever occurs frequently in acute brain injury patients, and its occurrence is associated with poorer outcomes. Paracetamol, an antipyretic frequently employed in patients with cerebral damage, may cause hypotension. We evaluated the cerebral and hemodynamic effects of intravenous (IV) paracetamol for the control of fever in Neuro-Intensive Care Unit (NICU) patients.

METHODS

This is a prospective observational study in which we enrolled 32 NICU patients: Subarachnoid Hemorrhage (SAH, n = 18), Traumatic Brain Injury (TBI, n = 10), Intracerebral Hemorrhage (ICH, n = 2) and Acute Ischemic Stroke (AIS, n = 2).

RESULTS

The administration of paracetamol resulted in a decrease of core body temperature (Tc) (p = 0,0001), mean arterial pressure (MAP) (p = 0,0006), cerebral perfusion pressure (CPP) (p = 0,0033), and jugular venous oxygen saturation (SjVO2) (p = 0.0193), and in an increase of arteriojugular venous differences of oxygen (AVDO2) (p = 0.0012). The proportion of patients who had an infusion of norepinephrine increased from 47 % to 75 % (p = 0.0039 McNemar Test). When intracranial pressure (ICP) at the start of paracetamol infusion (t-0) was compared with the measurement of ICP after 2 h, a significant correlation was observed (r = 0.669, p = 0.0002). This marked and significant correlation can be explained by the fact that for the higher levels of ICP assessed at t-0 (greater than 15 mmHg), we observed a marked reduction of ICP concomitant with the decrease of Tc. No problems related to norepinephrine administration and/or increase in dosage were observed.

CONCLUSION

Paracetamol administration is effective but exposes patients to hypotensive episodes that must be recognized and treated expeditiously to prevent further damage to the injured brain.

Covariates of intravenous paracetamol pharmacokinetics in adults

BACKGROUND

Pharmacokinetic estimates for intravenous paracetamol in individual adult cohorts are different to a certain extent, and understanding the covariates of these differences may guide dose individualization. In order to assess covariate effects of intravenous paracetamol disposition in adults, pharmacokinetic data on discrete studies were pooled.

METHODS

This pooled analysis was based on 7 studies, resulting in 2755 time-concentration observations in 189 adults (mean age 46 SD 23 years; weight 73 SD 13 kg) given intravenous paracetamol. The effects of size, age, pregnancy and other clinical settings (intensive care, high dependency, orthopaedic or abdominal surgery) on clearance and volume of distribution were explored using non-linear mixed effects models.

RESULTS

Paracetamol disposition was best described using normal fat mass (NFM) with allometric scaling as a size descriptor. A three-compartment linear disposition model revealed that the population parameter estimates (between subject variability,%) were central volume (V1) 24.6 (55.5%) L/70 kg with peripheral volumes of distribution V2 23.1 (49.6%) L/70 kg and V3 30.6 (78.9%) L/70 kg. Clearance (CL) was 16.7 (24.6%) L/h/70 kg and inter-compartment clearances were Q2 67.3 (25.7%) L/h/70 kg and Q3 2.04 (71.3%) L/h/70 kg. Clearance and V2 decreased only slightly with age. Sex differences in clearance were minor and of no significance. Clearance, relative to median values, was increased during pregnancy (F(PREG) = 1.14) and decreased during abdominal surgery (F(ABDCL) = 0.715). Patients undergoing orthopaedic surgery had a reduced V2 (F(ORTHOV) = 0.649), while those in intensive care had increased V2 (F(ICV) = 1.51).

CONCLUSIONS

Size and age are important covariates for paracetamol pharmacokinetics explaining approximately 40% of clearance and V2 variability. Dose individualization in adult subpopulations would achieve little benefit in the scenarios explored.

Best practice for fever management with intravenous acetaminophen in pediatric oncology

Intravenous (IV) acetaminophen was introduced in the United States in 2011 for use as an analgesic and antipyretic agent. While no studies have looked at its utilization specifically in the pediatric oncology population, existing literature suggests IV acetaminophen is safe and effective to use in both children and adults. This article aims to review and apply current data in evaluating whether or not children with cancer can safely benefit from its use. This article provides clinical indications, safety and efficacy profiles, and nursing implications along with recommendations for future study regarding the use of IV acetaminophen in this population.

Therapeutic approaches for renal colic in the emergency department: a review article

Context:

Renal colic is frequently described as the worst pain ever experienced, and management of this intense pain is necessary. The object of our review was to discuss different approaches of pain control for patients with acute renal colic in the emergency department.

Evidence Acquisition:

Studies that discussed the treatment of renal colic pain were included in this review. We collected articles from reputable internet databases.

Results:

Our study showed that some new treatment approaches, such as the use of lidocaine or nerve blocks, can be used to control the severe and persistent pain of renal colic.

Conclusions:

Some new approaches are discussed and their impact on renal colic pain control was compared with traditional therapies. The effectiveness of the new approaches in this review is similar or even better than in traditional treatments.

Pharmacotherapy of fever control among hospitalized adult patients

INTRODUCTION

Fever is common and associated with increased mortality among hospitalized adults. This article will review the pharmacotherapy of commonly prescribed antipyretic drugs including the rationale for and against temperature control in febrile adults, as well as the evidence associated with fever control in specific patient populations.

AREAS COVERED

Though fever is common, the molecular basis of pyrexia, and the interaction of these pathways with commonly prescribed antipyretic drugs are not fully understood. Furthermore, while experimental and clinical studies clearly demonstrate that pyrexia is harmful in select patients, available clinical trial data are unable to suggest an evidence-based approach to the treatment of fever. Interestingly, this also applies to patients with an acute neurologic injury wherein the treatment of fever with antipyretic therapy has become a common management strategy.

EXPERT OPINION

Few adequately powered clinical trials have investigated temperature control strategies in febrile patients. Therefore, it is not possible to define an evidence-based approach to the control of fever in hospitalized adults. Further clinical and translational research is required to identify the patients most likely to benefit from a strategy of fever control versus permissive hyperthermia, and to determine the antipyretic therapies associated with the greatest improvement in outcome.

Intravenous acetaminophen: a review of pharmacoeconomic science for perioperative use

Hospitals are subject to more economic pressures than ever before. On the one hand, cost containment or cost reduction is paramount, particularly in relation to costly branded pharmaceuticals. On the other hand, quality measures and value-based reimbursement penalizes poor patient care. Multimodal analgesia sits squarely in this quandary, since its very nature requires use of multiple drugs with their associated costs, though this approach has the potential to improve quality of care. We undertook a comprehensive review of the pharmacoeconomics of IV acetaminophen, a new drug useful as part of a multimodal analgesic approach. While this new branded drug adds to direct drug costs, there is clear potential for IV acetaminophen to reduce the incidence of opioid-related adverse events and, in so doing, result in net hospital savings. This review describes many clinical studies showing significant improvements in postoperative nausea and vomiting, excessive sedation and pruritus. In addition, we describe studies demonstrating faster recovery times in the post-anesthesia care unit, intensive care unit and total hospital length of stay. Lastly, we summarize many studies demonstrating the robust effect of IV acetaminophen on patient satisfaction. A holistic view of total hospital performance should be adopted when reviewing drugs rather than a silo mentality within the pharmacy. While IV acetaminophen adds to drug costs, the body of evidence indicates this drug has the potential to improve outcomes and hospital efficiency.

Intravenous paracetamol and dipyrone for postoperative analgesia after day-case tonsillectomy in children: a prospective, randomized, double blind, placebo controlled study

Tonsillectomy is associated with severe postoperative pain for which, several drugs are employed for management.

Objective

In this double-blind, placebo-controlled study we aimed to evaluate the efficacy of intravenous paracetamol and dipyrone when used for post-tonsillectomy analgesia in children.

Method

120 children aged 3-6 yr, undergoing tonsillectomy with or without adenoidectomy and/ or ventilation tube insertion were randomized to receive intraoperative infusions of paracetamol (15 mg/kg), dipyrone (15 mg/kg) or placebo (0.9% NaCl). Evaluation was carried out at 0.25, 0.50, 1, 2, 4, 6h postoperatively. Pethidine 0.25 mg/kg was utilized as rescue analgesic. Cumulative pethidine requirement was the primary outcome. Pain intensity measurement, pain relief, sedation level, nausea and vomiting, postoperative bleeding and any other adverse effects were noted.

Results

No significant difference was found in pethidine requirement between paracetamol and dipyrone groups. Cumulative pethidine requirement was significantly less in paracetamol and dipyrone groups vs. placebo. No significant difference was observed between groups in postoperative pain intensity scores throughout the study.

Conclusion

Intravenous paracetamol is found to have a similar analgesic efficacy as intravenous dipyrone and they both help to reduce the opioid requirement for postoperative analgesia in pediatric day-case tonsillectomy.

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.

Clinical pharmacology of intravenous paracetamol in perinatal medicine

Clinical pharmacology aims to predict drug-related effects based on compound and population specific pharmacokinetics (PK, concentration-time), and pharmacodynamics (PD, concentration-effect). Consequently, dosing needs to be based on the physiological characteristics of the individual patient. Pregnancy and early infancy hereby warrant focused assessment. The specific characteristics of both subpopulations will be illustrated based on observations on intravenous (iv) paracetamol PK and PD collected in these specific populations. At delivery, there is a significant higher paracetamol clearance (+ 45%, L/h) when compared to non-pregnant observations. This higher clearance is in part explained by a proportional increase in oxidative metabolite production, but mainly an increase in glucuronidation. When focusing on PD, an association between maternal paracetamol exposure and atopy in infancy and fetal gastroshizis has been reported. In early infancy, paracetamol clearance is significantly lower and mainly depends on size (weight 0.75), while also the distribution volume is higher (L/kg). Reports on hepatic tolerance, haemodynamic stability and impact of body temperature have been published while the concentration effect profile for analgesia seems to be similar between neonates and children. Similar to maternal exposure, there are reports on the association with atopy. Studies on the use of paracetamol to close the patent ductus arteriosus are ongoing. At least, these observations provide evidence on the need to study commonly administered anesthetics in such specific subpopulations with specific focus on both population specific PK and PD to further improve patient tailored pharmacotherapy.

Intravenous paracetamol versus dexketoprofen versus morphine in acute mechanical low back pain in the emergency department: a randomised double-blind controlled trial

STUDY OBJECTIVE

The objective of this study was to determine the analgesic efficacy and safety of intravenous, single-dose paracetamol versus dexketoprofen versus morphine in patients presenting with mechanical low back pain (LBP) to the emergency department (ED).

METHODS

This randomised double-blind study compared the efficacy of intravenous 1 gm paracetamol, 50 mg dexketoprofen and 0.1 mg/kg morphine in patients with acute mechanical LBP. Visual analogue scale (VAS) was used for pain measurement at baseline, after 15 and after 30 min.

RESULTS

A total of 874 patients were eligible for the study, and 137 of them were included in the final analysis: 46 patients from the paracetamol group, 46 patients in the dexketoprofen group and 45 patients in the morphine group. The mean age of study subjects was 31.5 ± 9.5 years, and 60.6% (n=83) of them were men. The median reduction in VAS score at the 30th minute for the paracetamol group was 65 mm (95% CI 58 to 72), 67 mm (95% CI 60 to 73) for the morphine group and 58 mm (95% CI 50 to 64) for the dexketoprophen group. Although morphine was not superior to paracetamol at 30 min (difference: 3.8 ± 4.9 (95% CI -6 to 14), the difference between morphine and dexketoprofen in reducing pain was 11.2 ± 4.7 (95% CI 2 to 21). At least one adverse effect occurred in 8.7% (n=4) of the cases in the paracetamol group, 15.5% (n=7) of the morphine group, and 8.7% (n=4) of the dexketoprophen group (p=0.482).

CONCLUSIONS

Intravenous paracetamol, dexketoprofen and morphine are not superior to each other for the treatment of mechanical LBP in ED.

Experimental Model of Spinal Cord Injury (SCI) in rats: management guidelines

Surgical experiments with laboratory animals are necessary for medical research. These studies aim to clarify the mechanism of disease, investigate the action and efficacy of new drugs or biological markers, as well as develop and enhance new therapies and apply new techniques. Regarding the models of spinal cord injury (SCI), there are several different methods that address the handling of the animals, especially concerning the use of analgesics, antibiotics and pre- and postoperative management. The lack of uniformity and standardization among the studies does not allow the understanding of the model of SCI or the proper handling of the paraplegic animals, hampering the adequate interpretation and comparison of results. The goal of this study is to establish a standard protocol on the handling of animals subjected to experimental models of SCI.

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.

Role of intravenous acetaminophen in postoperative pain management

SUMMARY The need to safely treat the postoperative pain of patients is apparent. Opioids, although effective, have multiple morbidities associated with their use. A multimodal approach to postoperative pain management can serve to minimize the undesirable effects of opioids. Intravenous acetaminophen (paracetamol) has recently become available in the USA where many practitioners are not familiar with this drug. This article reviews the history, pharmacology and clinical uses of intravenous acetaminophen in the treatment of perioperative pain.

Safety and population pharmacokinetic analysis of intravenous acetaminophen in neonates, infants, children, and adolescents with pain or Fever

OBJECTIVES

The administration of acetaminophen via the oral and rectal routes may be contraindicated in specific clinical settings. Intravenous administration provides an alternative route for fever reduction and analgesia. This phase 1 study of intravenous acetaminophen (Ofirmev, Cadence Pharmaceuticals, Inc., San Diego, CA) in inpatient pediatric patients with pain or fever requiring intravenous therapy was designed to assess the safety and pharmacokinetics of repeated doses over 48 hours.

METHODS

Neonates (full-term to 28 days) received either 12.5 mg/kg every 6 hours or 15 mg/kg every 8 hours. Infants (29 days to <2 years), children (2 to <12 years) and adolescents (≥12 years) received either 12.5 mg/kg every 4 hours or 15 mg/kg every 6 hours. Both noncompartmental and population nonlinear mixed-effects modeling approaches were used. Urinary metabolite data were analyzed, and safety and tolerability were assessed.

RESULTS

Pharmacokinetic parameters of acetaminophen were estimated using a two-compartment disposition model with weight allometrically expressed on clearances and central and peripheral volumes of distribution (Vds). Postnatal age, with a maturation function, was a significant covariate on clearance. Total systemic normalized clearance was 18.4 L/hr per 70 kg, with a plateau reached at approximately 2 years. Total central and peripheral Vds of acetaminophen were 16 and 59.5 L/70 kg, respectively. The drug was well tolerated based on the incidence of adverse events. The primary and minor pathways of elimination were acetaminophen glucuronidation, sulfation, and glutathione conjugate metabolites across all age groups.

CONCLUSIONS

Intravenous acetaminophen in infants, children, and adolescents was well tolerated and achieved plasma concentrations similar to those achieved with labeled 15 mg/kg body weight doses by oral or rectal administration.

Prevention of chronic pain after surgical nerve injury: amputation and thoracotomy

Although techniques for acute pain management have improved in recent years, a dramatic reduction in the incidence and severity of chronic pain following surgery has not occurred. Amputation and thoracotomy, although technically different, share the commonalities of unavoidable nerve injury and the frequent presence of persistent postsurgical neuropathic pain. The authors review the risk factors for the development of chronic pain following these surgeries and the current evidence that supports analgesic interventions. The inconclusive results from many preemptive analgesic studies may require us to reconceptualize the perioperative treatment period as a time of gradual neurologic remodeling.

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.

Paediatric drug development: are population models predictive of pharmacokinetics across paediatric populations?

AIMS

To assess the predictive value of a model-based approach for dose selection across paediatric populations in early clinical drug development.

METHODS

Abacavir was selected as a paradigm compound using data across a wide age range. Abacavir pharmacokinetics (PK) in children were analysed separately from infants and toddlers. Two independent models were obtained, and systemic exposure (AUC) was then simulated across populations based on the estimates from each model. Drug exposures in infants and toddlers were predicted using pharmacokinetic parameter distributions obtained from children, and the other way around.

RESULTS

The pharmacokinetic models (a two-compartment PK model for infants and toddlers and a one compartment PK model for children) accurately described the exposure in the population from which they were built. However, neither model predicted exposure in a different population: in infants, the median AUC (95%(-) CI) was estimated at 7.03 (6.72, 7.48) µg ml(-1) h, whilst it was predicted at 5.75 (4.82, 6.26) µg ml(-1) h; in children, the estimated median AUC was 6.96 (5.85, 7.91) µg ml(-1) h, whilst the predicted value was 6.45 (5.80, 7.01) µg ml(-1) h.

CONCLUSIONS

These findings suggest that the assumption of an identical (linear or nonlinear) correlation between pharmacokinetic parameters and demographic factors may not hold true across age groups. Whilst the use of modelling enables accurate characterization of pharmacokinetic properties, extrapolations based on such parameter estimates may have limited value due to differences in the impact of developmental growth across populations.

Strategies Aimed at Preventing Chronic Post-surgical Pain: Comprehensive Perioperative Pain Management after Total Joint Replacement Surgery

PURPOSE

Chronic post-surgical pain (CPSP) is a frequent outcome of musculoskeletal surgery. Physiotherapists often treat patients with pain before and after musculoskeletal surgery. The purposes of this paper are (1) to raise awareness of the nature, mechanisms, and significance of CPSP; and (2) to highlight the necessity for an inter-professional team to understand and address its complexity. Using total joint replacement surgeries as a model, we provide a review of pain mechanisms and pain management strategies.

SUMMARY OF KEY POINTS

By understanding the mechanisms by which pain alters the body's normal physiological responses to surgery, clinicians selectively target pain in post-surgical patients through the use of multi-modal management strategies. Clinicians should not assume that patients receiving multiple medications have a problem with pain. Rather, the modern-day approach is to manage pain using preventive strategies, with the aims of reducing the intensity of acute postoperative pain and minimizing the development of CPSP.

CONCLUSIONS

The roles of biological, surgical, psychosocial, and patient-related risk factors in the transition to pain chronicity require further investigation if we are to better understand their relationships with pain. Measuring pain intensity and analgesic use is not sufficient. Proper evaluation and management of risk factors for CPSP require inter-professional teams to characterize a patient's experience of postoperative pain and to examine pain arising during functional activities.

Use of intravenous acetaminophen in the treatment of postoperative pain

Pain management is a crucial component in the care of the postoperative patient. Although there have been innovative advances in pain management and new analgesic modalities, a need still exists for safer and more tolerable analgesics for the management of pain in the postoperative setting. An intravenous formulation of acetaminophen has been available in Europe for more than 20 years and may soon be reaching the US market. Intravenous acetaminophen may help reduce the consumption of opioid analgesics and has a safety and tolerability profile comparable to placebo. This review will discuss the novel characteristics of intravenous acetaminophen that may make it an attractive choice for the management of acute pain in the postoperative period.

Continuous multimechanistic postoperative analgesia: a rationale for transitioning from intravenous acetaminophen and opioids to oral formulations

Good surgical outcomes depend in part on good pain relief, allowing for early mobilization, optimal recovery, and patient satisfaction. Postsurgical pain has multiple mechanisms, and multimechanistic approaches to postoperative analgesia are recommended and may be associated with improved pain relief, lowered opioid doses, and sometimes a lower rate of opioid-associated side effects. Acetaminophen (paracetamol) is a familiar agent for treating many types of pain, including postsurgical pain. Oral acetaminophen has been shown to be safe and effective in a variety of acute pain models. Combination products using a fixed-dose of acetaminophen and an opioid have also been effective in treating postsurgical pain. Combination products with acetaminophen have demonstrated an opioid-sparing effect, which inconsistently results in a reduced rate of opioid-associated side effects. Intravenous (IV) acetaminophen and an opioid analgesic administered in the perioperative period may be followed by an oral acetaminophen and opioid combination in the postoperative period. Transitioning from an IV acetaminophen and opioid formulation to a similar but oral formulation of the same drugs appears to be a reasonable step in that both analgesic therapies are known to be safe and effective. For postsurgical analgesia with any acetaminophen product, patient education is necessary to be sure that the patient does not concurrently take any over-the-counter products containing acetaminophen and accidentally exceed dose limits.

A randomized study of the efficacy and safety of intravenous acetaminophen compared to oral acetaminophen for the treatment of fever

OBJECTIVES

The purpose of this study was to assess the safety and dynamics of the onset of antipyretic efficacy of intravenous (IV) acetaminophen versus oral (PO) acetaminophen in the treatment of endotoxin-induced fever.

METHODS

This randomized, double-blind, double-dummy, single-dose study was conducted at a single center in the United States in healthy volunteer adult males with an endotoxin-induced fever to assess the antipyretic efficacy and safety of IV acetaminophen 1 g versus PO acetaminophen 1 g over 6 hours. Subjects who achieved a sufficient fever response to a test dose of reference standard endotoxin were randomly assigned to receive either IV acetaminophen and PO placebo (n = 54) or PO acetaminophen and IV placebo (n = 51). The primary efficacy outcome was the weighted sum of temperature differences from baseline at time T0 through T120 minutes. Safety evaluations included adverse event (AE), physical exam, and laboratory assessments.

RESULTS

Of 105 subjects receiving study medication, 24 vomited within 2 hours postdose (PO acetaminophen, n = 15; and IV acetaminophen, n = 9) and were excluded from the modified intent-to-treat population that consisted of 36 and 45 subjects treated with PO and IV acetaminophen, respectively. While this was done to not confer an advantage to the IV formulation, a sensitivity analysis including these subjects did not change the overall efficacy results. Statistically significant results favoring IV acetaminophen were observed for the primary endpoint (weighted sum of temperature differences over 120 minutes, p = 0.0039) and also at each time point from T30 to T90 minutes, although the maximum mean observed temperature difference was only 0.3°C. The study drugs were well tolerated. The AE frequency was comparable between the IV and PO groups.

CONCLUSIONS

A single dose of IV acetaminophen is as safe and effective in reducing endotoxin-induced fever as PO acetaminophen. IV acetaminophen may be useful where patients are unable to tolerate PO intake or when an earlier onset of action is desirable.

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.

Banning front-of-package food labels: First Amendment constraints on public health policy

In recent months, the FDA has begun a crackdown on misleading nutrition and health claims on the front of food packages by issuing warning letters to manufacturers and promising to develop stricter regulatory standards. Leading nutrition policy experts Marion Nestle and David Ludwig have called for an even tougher approach: a ban on all nutrition and health claims on the front of food packages. Nestle and Ludwig argue that most of these claims are scientifically unsound and misleading to consumers and that eliminating them would ‘aid educational efforts to encourage the public to eat whole or minimally processed foods and to read the ingredients list on processed foods’. Nestle and Ludwig are right to raise concerns about consumer protection and public health when it comes to front-of-package food labels, but an outright ban on front-of-package nutrition and health claims would violate the First Amendment. As nutrition policy experts develop efforts to regulate front-of-package nutrition and health claims, they should be mindful of First Amendment constraints on government regulation of commercial speech.

Pharmacologic management of acute pediatric pain

The accurate assessment and effective treatment of acute pain in children in the hospital setting is a high priority. During the past 2 to 3 decades, pediatric pain management has gained tremendous knowledge with respect to the understanding of developmental neurobiology, developmental pharmacology the use of analgesics in children, the use of regional techniques in children, and of the psychological needs of children in pain. A wide range of medications is available to treat a variety of pain types. This article provides an overview of the most common analgesic medications and techniques used to treat acute pain in children.