Early bioavailability of paracetamol after oral or intravenous administration

Is there a role for intravenous acetaminophen in pediatric emergency departments?

BACKGROUND

As a nonopioid parenteral analgesic intravenous (IV) acetaminophen is potentially attractive for emergency department (ED) use. However, there is little experience with its use in the pediatric ED setting. We introduced the agent into a pediatric ED with a preliminary restrictive prescribing regimen and describe its use.

METHODS

This is a retrospective record review of all patients who had received IV acetaminophen over 12 months. Prescribing indications were for analgesia only (not for fever management) in patients at risk of opioid-related adverse events. We assessed the demographics, dosing, presenting complaints, discharge diagnoses, and indications for IV acetaminophen use.

RESULTS

Thirty-one patients received IV acetaminophen (mean age, 10 years). All patients were at least moderately sick according to their triage assessment. The median dose was 15 mg/kg with a median of 1 dose administered. Presenting complaints were mainly trauma, abdominal complaints, and sepsis/fever/neutropenia. Thirty-nine percent of patients had severe underlying conditions. Two patients died: 1 patient had a chronic neurological condition, and the other was undergoing palliative treatment for cancer. Physicians complied with prescribing indications for half the patients: 53% were at risk of opioid-related adverse events. Physicians prescribed outside the initial indications as part of multimodal analgesia (13%), for complex patients with fever and pain (7%), and for fever only in patients unable to tolerate enteral administration (27%).

CONCLUSIONS

In the setting of an initial restrictive prescribing regimen, IV acetaminophen was used in a small number of pediatric ED patients. In addition to use in patients at risk of opioid adverse events, the medication was also used in complex patients who were unable to tolerate an enteral formulation. Emergency department prescribing guidelines have been modified accordingly.

Randomised controlled trial comparing oral and intravenous paracetamol (acetaminophen) plasma levels when given as preoperative analgesia

Gastric absorption of oral paracetamol (acetaminophen) may be unreliable perioperatively in the starved and stressed patient. We compared plasma concentrations of parenteral paracetamol given preoperatively and oral paracetamol when given as premedication. Patients scheduled for elective ear; nose and throat surgery or orthopaedic surgery were randomised to receive either oral or intravenous paracetamol as preoperative medication. The oral dose was given 30 minutes before induction of anaesthesia and the intravenous dose given pre-induction. All patients were given a standardised anaesthetic by the same specialist anaesthetist who took blood for paracetamol concentrations 30 minutes after the first dose and then at 30 minute intervals for 240 minutes. Therapeutic concentrations of paracetamol were reached in 96% of patients who had received the drug parenterally, and 67% of patients who had received it orally. Maximum median plasma concentrations were 19 mg.l(-1) (interquartile range 15 to 23 mg.l(-1)) and 13 mg.l(-1) (interquartile range 0 to 18 mg.l(-1)) for the intravenous and oral group respectively. The difference between intravenous and oral groups was less marked after 150 minutes but the intravenous preparation gave higher plasma concentrations throughout the study period. It can be concluded that paracetamol gives more reliable therapeutic plasma concentrations when given intravenously.

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.

Evaluation of pain following supratentorial craniotomy

BACKGROUND

Craniotomy is considered less painful than other surgical procedures and supratentorial surgeries are thought to be the least painful among them. We studied the intensity of pain in the postoperative period following a supratentorial craniotomy while using oral paracetamol as the sole analgesic. The effect of temporalis muscle incision on the intensity of pain was also studied.

METHODS

In a prospective study over 6 months, 43 patients with a pre-operative Glasgow coma scale (GCS) score 15/15, aged  >16 years who underwent a supratentorial craniotomy and were admitted to neurosurgical ICU were included in the study. Patients with a postoperative GCS score of  <15 on admission to the ICU were excluded from the study. All patients received oral paracetamol for pain relief. Postoperative pain scale was used in the first hour to assess pain objectively. Visual analogue scale was used thereafter to record pain at 8, 12, 24 and 48 h post-craniotomy. Patients were familiarised with these scales preoperatively. Postoperative pain scores were compared with preoperative scores using paired T test, whereas significance of temporalis muscle involvement in incision for increased post-craniotomy pain was evaluated using Fischer's exact test.

RESULTS

Inadequate analgesia was complained of by 63% (n = 27) patients in the first 12 h postoperatively. However, severe pain was present only in 12% (n = 5) of patients. Incidence of pain decreased thereafter at 24 and 48 h. Twenty-seven percent (n = 12) patients were free of pain at all study periods. Fifty percent (n = 3) of patients who complained of significant pain beyond 12 h developed postoperative complications. Incision of temporalis muscle was not associated with a significant increase in severity of postoperative pain.

CONCLUSION

Pain following craniotomy is adequately addressed in only about 27% of patients with oral paracetamol. However, the long-term analgesic effect is satisfactory. Persistence of pain of moderate or severe intensity 24 h after a craniotomy could suggest an impending postoperative complication.

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.

Oral acetaminophen (paracetamol) for additional analgesia in phacoemulsification cataract surgery performed using topical anesthesia Randomized double-masked placebo-controlled trial

PURPOSE

To evaluate the clinical analgesic efficacy of 1.0 g oral acetaminophen (paracetamol) given in addition to topical anesthesia before phacoemulsification cataract surgery.

SETTING

Inpatient and outpatient ophthalmology clinics, Bydgoszcz, Poland.

METHODS

Consecutive patients with age-related cataract having phacoemulsification under topical anesthesia (tetracaine 0.5%) were enrolled in a prospective double-blind randomized placebo-controlled study. Patients were randomly assigned to preoperative oral administration of a placebo medication or to oral administration of 1.0 g acetaminophen. The main outcome measure was intensity of pain during and after surgery. Pain intensity was measured using a 10 cm baseline visual analog scale and a discrete 5-category verbal rating scale.

RESULTS

The study comprised 160 consecutive patients (80 in each group). Intraoperatively, the mean visual analog scale pain intensity score was 2.17 +/- 1.81 in the placebo group and 1.45 +/- 1.17 in the acetaminophen group and the mean verbal rating scale score, 1.11 +/- 0.73 and 0.67 +/- 0.66, respectively (P<.01). Postoperatively, the mean visual analog scale score for pain was 1.47 +/- 1.39 in the placebo group and 0.56 +/- 0.61 in the acetaminophen group and the mean verbal rating scale score, 0.94 +/- 0.79 and 0.28 +/- 0.41, respectively (P<.01). There was no significant difference in patient behavior during surgery and no significant adverse effects of acetaminophen use.

CONCLUSION

Preoperative oral administration of acetaminophen 1.0 g was effective, convenient, safe, and cost effective in reducing intraoperative and postoperative pain in phacoemulsification performed using topical anesthesia.

Evidence for the use of non-steroidal anti-inflammatory drugs for acute pain in the post anaesthesia care unit

Successful management of acute post-operative pain in the post anaesthesia care unit (PACU) is vitally important. A multimodal approach incorporating analgesics with varying sites of action is recommended. Anti-inflammatory drugs are effective analgesics in the treatment of mild to moderate acute pain (Bandolier Oxford league table of analgesic efficacy 2007). The purpose of this article is to consider the evidence for the use of non-steroidal anti-inflammatory drugs (NSAIDs) for acute postoperative pain.

Consensus statement on the anticipation and prevention of acute postoperative pain: multidisciplinary RADAR approach

BACKGROUND

There has been considerable investment in efforts to improve postoperative pain management, including the introduction of acute pain teams. There have also been a number of guidelines published on postoperative pain management and there is widespread agreement on how pain should be practically managed. Despite these advances, there is no apparent improvement in the number of patients experiencing moderately severe or extreme pain after surgery. This highlights significant scope for improvement in acute postoperative pain management.

SCOPE

In January 2009, a multidisciplinary UK expert panel met to define and agree a practical framework to encourage implementation of the numerous guidelines and fundamentals of pain management at a local level. The panel recognised that to do this, there was a need to organise the information and guidelines into a simplified, accessible and easy-to-implement system based on their practical clinical experience. Given the volume of literature in this area, the Chair recommended that key international guidelines from professional bodies should be distributed and then reviewed during the meeting to form the basis of the framework. Consensus was reached by unanimous agreement of all ten participants.

FINDINGS

This report provides a framework for the key themes, including consensus recommendations based upon practical experience agreed during the meeting, with the aim of consolidating the key guidelines to provide a fundamental framework which is simple to teach and implement in all areas. Key priorities that emerged were: Responsibility, Anticipation, Discussion, Assessment and Response. This formed the basis of RADAR, a novel framework to help pain specialists educate the wider care team on understanding and prioritising the management of acute pain.

CONCLUSION

Acute postoperative pain can be more effectively managed if it is prioritised and anticipated by a well-informed care team who are educated with regard to appropriate analgesic options and understand what the long-term benefits of pain relief are. The principles of RADAR provide structure to help with training and implementation of good practice, to achieve effective postoperative pain management.

Paracetamol versus metamizol in the treatment of postoperative pain after breast surgery: a randomized, controlled trial

BACKGROUND AND OBJECTIVE

Intravenously administered paracetamol is an effective analgesic in postoperative pain management. However, there is a lack of data on the effect of intravenous (i.v.) paracetamol on pain following soft tissue surgery.

METHODS

Eighty-seven patients undergoing elective breast surgery with total i.v. anaesthesia (propofol/remifentanil) were randomized to three groups. Group para received 1 g i.v. paracetamol 20 min before and 4, 10 and 16 h after the end of the operation. Group meta and plac received 1 g i.v. metamizol or placebo, respectively, scheduled at the same time points. All patients had access to i.v. morphine on demand to achieve adequate pain relief.

RESULTS

No significant difference in total morphine consumption between groups was detectable. The proportion of patients who did not receive any morphine in the postoperative period was significantly higher in group para (42%) than in group plac (4%). Ambulation was significantly (P < 0.05) earlier in group para (4.0 +/- 0.2 h) than in groups meta (4.6 +/- 0.2 h) and plac (5.5 +/- 1.0 h). No differences were observed between groups meta and plac. There were no differences between groups with regard to incidence of postoperative nausea and vomiting or changes in vigilance.

CONCLUSION

Neither i.v. paracetamol nor i.v. metamizol provided a significant reduction in total postoperative morphine consumption compared with placebo in the management of postoperative pain after elective breast surgery. Administration of paracetamol resulted in a significant reduction in the number of patients needing opioid analgesics to achieve adequate postoperative pain relief.

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.

Randomized controlled trial of duration of analgesia following intravenous or rectal acetaminophen after adenotonsillectomy in children

BACKGROUND

Doses of acetaminophen 40 mg kg(-1) rectally and 15 mg kg(-1) i.v. produce similar effect-site concentrations. However, the clinical effectiveness of these routes has not been compared. The aim of this study was to compare duration and efficacy of analgesia in children following adenotonsillectomy after acetaminophen either 40 mg kg(-1) rectally or 15 mg kg(-1) i.v.

METHODS

Fifty children aged between 2 and 5 yr were recruited. They received a standardized anaesthetic, including 2 microg kg(-1) of fentanyl. Children were randomized to receive either rectal or i.v. acetaminophen. Postoperative pain was assessed regularly with the Children and Infants Postoperative Pain Scale score and rescue analgesia provided if scores were 4 or greater. The primary outcome measure was time to first analgesia. Results were plotted with a Kaplan-Meier analysis and median time to rescue analgesia compared between the groups.

RESULTS

The protocol was successfully completed in 46 children. Forty-five children required rescue medication. The time to first rescue analgesia was longer in children receiving rectal acetaminophen (median 10 h, inter-quartile range 9-11 h) compared with those receiving i.v. acetaminophen (7, 6-10 h) with a P-value of 0.01 by log-rank test for equality in survivor function. Few children in either group required rescue analgesia within the first 6 h with differences between the groups being most prominent in the period from 6 to 10 h.

CONCLUSIONS

Rectal acetaminophen 40 mg kg(-1) provides longer analgesia for moderately painful procedures when compared with 15 mg kg(-1) acetaminophen i.v.

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.

Clinical practice and routines for day surgery in Sweden: results from a nation-wide survey

BACKGROUND

Day surgery has expanded considerably during the last decades. Routines and standards have developed but differ between and within countries.

METHODS

We studied the practice of day surgery in Sweden by an extensive questionnaire survey sent to all 92 hospitals.

RESULTS

The proportion of day surgery vs. in-hospital procedures was overall 43%, with 43% in adults and 46% in children. Orthopaedic (33%), general (29%) and gynaecological (17%) surgery were the most common ambulatory procedures. Most patients (>90%) underwent pre-operative assessment by an anaesthesiologist. Patient self-assessment questionnaires were common (86%). Risk stratification for post-operative nausea and vomiting was used by 70% of the departments. Anxiolytic pre-medication was uncommon. Most anaesthesiologists (95%) used pre-operative oral analgesics to initiate post-operative analgesia, the most common being paracetamol (95%), NSAIDs (73%) and coxibs (15%). A balanced general anaesthesia technique was preferred. Post-operatively, 93% of the units routinely assessed patients' pain. Analgesic combinations of paracetamol, NSAIDs and weak opioids were used by 94% of the units. Most hospitals (80%) had standardised discharge criteria based on clinical assessment, and many required a patient escort at home for 24 h post-operatively. Assessments of unplanned admission, re-admission and post-operative complications were not performed routinely. Follow-up telephone calls within 1-2 days were performed regularly in about 40% of the units, or in selected patients only (37%). Pain was the most frequent complaint on follow-up.

CONCLUSIONS

In Sweden, a high degree of standardised regime for day surgical practice was found. Post-operative pain is the most common complaint after discharge.

Multi-modal-analgesia for pain management after Hallux Valgus surgery: a prospective randomised study on the effect of ankle block

BACKGROUND

Pain and emesis are the two major complaints after day case surgery. Local anaesthesia has become an important part of optimizing intra and post-operative pain treatment, but is sometimes not entirely sufficient. The aim of the present study was to study the effect of adding an ankle block to a multi-modal analgesic approach on the first 24-hour-need for rescue analgesia in patients undergoing elective Hallux Valgus surgery.

TYPE OF STUDY

Prospective, randomized patient-blind study comparing ankle block with levo-bupivacaine, lidocaine and Saline placebo control.

METHODS

Ninety patients were studied comparing ankle block (15 cc) using levo-bupivacaine 2.5 mg/ml, lidocaine 10 mg/ml or placebo (saline) on day-case elective Hallux Valgus surgery, supported by general anaesthesia in all cases. Primary study endpoint was number of patient's requiring oral analgesics during the first 24 post-operative hours.

RESULTS

Ankle block had no effect on need for rescue analgesia and pain ratings during the 1st 24 postoperative hours, there was no difference seen between placebo and any of the two active local anaesthesia studied. The only differences seen was that both lidocaine and levo-bupivacaine reduced the intra-operative need for anaesthetic (sevoflurane) and that levo-bupivacaine patients had a lower need as compared to the lidocaine patients for oral analgesics during the afternoon of surgery.

CONCLUSION

Adding a single shot ankle block to a multi-modal pain management strategy reduces the need for intra-operative anaesthesia but has no major impact of need of rescue analgesics or pain during the first 24-hour after surgery.

Intravenous paracetamol: a review of efficacy and safety in therapeutic use

Paracetamol is well established as a leading nonprescription antipyretic analgesic drug and is available in oral, rectal or intravenous forms. However, except for oral paracetamol, there is a marked discrepancy between the extent to which paracetamol is used and the available evidence for an analgesic effect in postoperative pain. This review mainly focuses on intravenous paracetamol. Its efficacy and safety are analyzed, as well as its use in therapeutics, alone or in combination. The morphine-sparing, additive and antihyperalgesia effects of intravenous paracetamol are also reviewed. The analyses are divided into several sections, comparing the efficacy of intravenous paracetamol with placebo, other forms of paracetamol or analgesic agents and analyzing its efficacy in multimodal therapy combined with NSAIDs or a morphinic agent.

Postoperative pain treatment for ambulatory surgery

One of the most significant changes in surgical practice during the last two decades has been the growth of ambulatory surgery. Adequate postoperative analgesia is a prerequisite for successful ambulatory surgery. Recent studies have shown that large numbers of patients suffer from moderate to severe pain during the first 24-48 hr. The success of fast-tracking depends to a considerable extent on effective postoperative pain management routines and the cost saving of outpatient surgery may be negated by unanticipated hospital admission for poorly treated pain. Depending on the intensity of postoperative pain current management includes the use of analgesics such as paracetamol, NSAIDs including coxibs and tramadol as single drugs or in combination as part of balanced (multimodal) analgesia. However, in the ambulatory setting many patients suffer from pain at home in spite of multimodal analgesic regimens. Sending patients home with perineural, incisional, and intra-articular catheters is a new and evolving area of postoperative pain management. Current evidence suggests that these techniques are effective, feasible and safe in the home environment if appropriate patient selection routines and organization for follow-up are in place.

Update on the role of non-opioids for postoperative pain treatment

Non-opioids play an ever increasing role in the treatment of postoperative pain; either on their own for mild to moderate pain or in combination with other analgesic approaches, in particular opioids, as a component of multimodal analgesia. The analgesics paracetamol (acetaminophen) and dipyrone (metamizole) as well as compounds with an additional anti-inflammatory effect (non-selective non-steroidal anti-inflammatory drugs and selective cyclo-oxygenase-2 inhibitors) are used widely in the perioperative period. Paracetamol is gaining renewed interest in this setting due to its minimal adverse effects and recent availability in a parenteral preparation, but its benefits are insufficiently studied. Dipyrone continues to be used in many countries despite the ongoing debate on the incidence and relevance of its ability to cause agranulocytosis. Among the anti-inflammatory drugs, selective cyclo-oxygenase-2 inhibitors have the most supportive data for their beneficial effects as a component of multimodal analgesia and offer benefits with regard to their adverse effect profile.

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

BACKGROUND

Paracetamol is commonly used for post-operative pain management in combination with more potent analgesics. The best route of paracetamol administration after major surgery, when oral intake may not be optimal, is not known. Our primary purpose was to study plasma concentrations after the 1st and 4th dose of 1 g of paracetamol given either rectally or intravenously (i.v.) after major surgery.

METHODS

In this prospective, randomized study, 48 patients undergoing heart surgery were randomized upon arrival to the intensive care unit (ICU) to receive paracetamol every 6th hour either as suppositories or intravenous injections. In half the patients (n = 24), blood samples for paracetamol concentration were obtained before and 20, 40 and 80 min after the first dose. In the other patients (n = 24), additional samples were taken prior to, and at 20, 40, 80 min and 4 and 6 h after, the 4th dose.

RESULTS

Plasma paracetamol concentration peaked (95 +/- 36 micromol/l) within 40 min after initial i.v. administration but did not increase within 80 min after the 1st suppository. Plasma concentration before the 4th dose was 74 +/- 51 and 50 +/- 27 in the rectal and i.v. groups, respectively. Paracetamol concentration peaked 20 min after the 4th dose for the i.v. patients (210 +/- 84 micromol/l) and declined to 99 +/- 27 micromol/l at 80 min as compared with the rectal patients 69 +/- 44 to 77 +/- 48 micromol/l.

CONCLUSION

Both time course and peak plasma concentrations of paracetamol given rectally differ from the one seen after intravenous administration. The clinical impact of these differences needs further investigation.

Intravenous acetaminophen reduced the use of opioids compared with oral administration after coronary artery bypass grafting

OBJECTIVE

The purpose of this study was to evaluate if intravenous acetaminophen compared to oral administration reduced the consumption of opioids and their side effects without an increase in pain during the stay in the intensive care unit (ICU).

DESIGN

Prospective, randomized study.

SETTING

An ICU in a university hospital.

PARTICIPANTS

Eighty patients with written informed consent undergoing coronary artery bypass grafting with cardiopulmonary bypass. Anesthesia was based on propofol and fentanyl combined with sevoflurane.

INTERVENTIONS

Patients were randomized to 2 groups: acetaminophen, 1 g every sixth hour during the postoperative period, either as tablets or intravenously after extubation.

MEASUREMENTS AND MAIN RESULTS

The amount of opioids administered during the study period was measured starting with acetaminophen administration during the stay in the ICU until 9 o'clock the following morning. Incidence of postoperative nausea and vomiting (PONV) was noted. Pain was evaluated with a visual analog scale (VAS) from 0 to 10. Three patients, 2 in the oral and 1 in the intravenous group, were excluded because of incomplete data. The intravenous group received less opioids than the orally treated group, 17.4 +/- 7.9 mg compared with 22.1 +/- 8.6 mg (p = 0.016). PONV incidence and VAS scores did not differ. During the first hours after extubation, 50 of 77 patients reported VAS scores >3 with no difference between groups.

CONCLUSIONS

Intravenous acetaminophen had a limited opioid-sparing effect when compared with oral administration after coronary artery bypass graft surgery. The opioid-sparing effect was not accompanied by any reduction in the incidence of PONV. The clinical significance of the opioid-sparing effect could therefore be questioned.

Onset of acetaminophen analgesia: comparison of oral and intravenous routes after third molar surgery

BACKGROUND

The purpose of this randomized double-blind study was to compare the efficacy and safety of propacetamol 2 g (an i.v. acetaminophen 1 g formulation) administered as a 2-min bolus injection (n=50) or a 15-min infusion (n=50) with oral acetaminophen 1 g (n=50) or placebo (n=25) for analgesia after third molar surgery in patients with moderate to severe pain after impacted third molar removal.

METHODS

All patients were evaluated for efficacy during the initial 6 h period after treatment administration (T(0)) and for safety during the entire week after T(0).

RESULTS

The onset of analgesia after propacetamol was shorter (3 min for bolus administration, 5 min for 15-min infusion) than after oral acetaminophen (11 min). Active treatments were significantly better for all parameters (pain relief, pain intensity, patient's global evaluation, duration of analgesia) than placebo (P<0.05). Adverse events were more frequent after propacetamol, especially pain at the injection site. Propacetamol bolus resulted in a much higher incidence of local adverse events than the infusion (propacetamol bolus 90% vs propacetamol infusion 52%) with no clinically significant benefits in terms of analgesic efficacy.

CONCLUSION

I.V. propacetamol, administered as a 15-min infusion, is a fast-acting analgesic agent. It is more effective in terms of onset of analgesia than a similar dose of oral acetaminophen.

Multimodal Analgesia Techniques and Postoperative Rehabilitation

The concept of multimodal analgesia involves the use of different classes of analgesics and different sites of analgesic administration to provide superior dynamic pain relief with reduced analgesic-related side effects. Although multimodal analgesia techniques have assumed increasing importance in the management of perioperative pain, it has become increasingly apparent that postoperative outcome may not be improved. Nevertheless, the integration of multimodal analgesia techniques with a multimodal and multidisciplinary rehabilitation program may enhance recovery, reduce hospital stay, and facilitate early convalescence.

Influence of Medium and Temperature on the Hydrolysis Kinetics of Propacetamol Hydrochloride: Determination Using Derivative Spectrophotometry

Propacetamol hydrochloride (PRO) is a water-soluble prodrug of paracetamol (PA) which can be parenterally administered as analgesic for the treatment of postoperative pain, acute trauma, and gastric and/or intestinal disorders where oral administration is not possible. In these circumstances, PRO can be administered in physiologic or glucose solutions since it is rapidly and quantitatively hydrolyzed into PA by plasma estearases. We have studied the degradation kinetics of PRO in 5% glucose and 0.9% saline solutions at 4 degrees C and 25 degrees C (storage and room temperatures, respectively). The analytic technique used to determine PRO and PA quantitatively was first-derivative spectrophotometry. The degradation process of PRO can be best fitted to a second-order kinetics with independence of the medium used (saline or glucose solution). The hydrolysis kinetics of PRO conversion into PA depends on the temperature but not on the assay medium (saline or glucose solution). The degradation rate constants obtained for PRO were approximately 4.5 times higher at 25 degrees C than at 4 degrees C. The values of t(90%) for PRO were 3.17 h and 3.61 h at 25 degrees C, and 13.42 h and 12.36 h at 4 degrees C when the tests were performed in 5% glucose and 0.9% saline solutions, respectively.