4 Paracetamol and propacetamol for post-operative pain: contrasts to traditional NSAIDs

Pain Chemogenomics Knowledgebase (Pain-CKB) for Systems Pharmacology Target Mapping and Physiologically Based Pharmacokinetic Modeling Investigation of Opioid Drug-Drug Interactions

More than 50 million adults in America suffer from chronic pain. Opioids are commonly prescribed for their effectiveness in relieving many types of pain. However, excessive prescribing of opioids can lead to abuse, addiction, and death. Non-steroidal anti-inflammatory drugs (NSAIDs), another major class of analgesic, also have many problematic side effects including headache, dizziness, vomiting, diarrhea, nausea, constipation, reduced appetite, and drowsiness. There is an urgent need for the understanding of molecular mechanisms that underlie drug abuse and addiction to aid in the design of new preventive or therapeutic agents for pain management. To facilitate pain related small-molecule signaling pathway studies and the prediction of potential therapeutic target(s) for the treatment of pain, we have constructed a comprehensive platform of a pain domain-specific chemogenomics knowledgebase (Pain-CKB) with integrated data mining computing tools. Our new computing platform describes the chemical molecules, genes, proteins, and signaling pathways involved in pain regulation. Pain-CKB is implemented with a friendly user interface for the prediction of the relevant protein targets and analysis and visualization of the outputs, including HTDocking, TargetHunter, BBB predictor, and Spider Plot. Combining these with other novel tools, we performed three case studies to systematically demonstrate how further studies can be conducted based on the data generated from Pain-CKB and its algorithms and tools. First, systems pharmacology target mapping was carried out for four FDA approved analgesics in order to identify the known target and predict off-target interactions. Subsequently, the target mapping outcomes were applied to build physiologically based pharmacokinetic (PBPK) models for acetaminophen and fentanyl to explore the drug-drug interaction (DDI) between this pair of drugs. Finally, pharmaco-analytics was conducted to explore the detailed interaction pattern of acetaminophen reactive metabolite and its hepatotoxicity target, thioredoxin reductase.

Sub-Tenon's injection versus paracetamol in pediatric strabismus surgery

BACKGROUND

Emergence agitation, vomiting, and oculocardiac reflex (OCR) in children undergoing strabismus surgery under general anesthesia are common problems. The purpose of this study was to determine whether the effect of analgesia can reduce the incidence of these problems. We compared the effects of sub-Tenon's injection versus intravenous (IV) and rectal paracetamol in this surgery.

METHODS

In a prospective, randomized, double-blind study, ninety patients ranging in age from 4 to 8 years scheduled for extraocular muscle surgery for strabismus were included in this study. After induction of anesthesia, just before the surgery, children were divided into three groups (n = 30 for each group) Group A received sub-Tenon's anesthesia with 2.5% bupivacaine (0.08 ml/kg). Group B received IV paracetamol (20 mg/kg). Group C received paracetamol rectal suppository (40 mg/kg). The occurrence of oculocardiac reflex (OCR) intraoperatively was recorded. Then, in the Postanesthesia Care Unit, patients were assessed for their emergence behaviors. Vomiting was also noticed.

RESULTS

The OCR developed in few patients, and there was no significant difference between the groups. The highest number of patients with agitation was in Group C followed by Group B then Group A. Vomiting was significantly low in Group A followed by Group B then Group C.

CONCLUSION

Sub-Tenon block in strabismus surgery in children decreased the incidence of postoperative agitation and vomiting compared with IV paracetamol then rectal paracetamol. There was no difference between sub-Tenon block and paracetamol in the incidence of oculocardiac reflex.

Analgesic efficacy and safety of nefopam vs. propacetamol following hepatic resection

In order to compare the morphine-sparing effect, analgesic efficacy and tolerance of nefopam and propacetamol given at their highest recommended doses, 120 patients undergoing elective hepatic resection were randomly assigned to receive postoperative intravenous patient-controlled analgesia with morphine alone, or in combination with nefopam (20 mg.4 h-1) or propacetamol (2 g.6 h-1). Compared with the control group (43 [7-92] mg), median [range] cumulative morphine consumption for 24 h after the study started was halved in the nefopam group (21 [3-78] mg, p <0.001) and 20% lower in the propacetamol group (35 [6-84] mg, p = 0.15). Analgesia was superior in the nefopam group despite the lower morphine consumption. Adverse effects were comparable in the three groups, except for significantly more nausea in the control group (39% vs. 17 and 26% in the nefopam and propacetamol groups, respectively) and more sweating in the nefopam group (17% vs. 0 and 3% in the control and propacetamol groups, respectively). Overall patient satisfaction was better (p < 0.001) in patients given nefopam (97%) than those receiving morphine alone (82%) or propacetamol (74%).

Management of the paediatric patient

Recent introduction of new fast-onset short-duration anaesthetic drugs and the use of regional anaesthesia techniques in children have resulted in good control of anaesthesia and perioperative pain with few adverse effects. Ambulatory surgery has gained popularity in paediatric practice, particularly as children are often otherwise healthy and usually undergo minor surgery.

Patient-controlled analgesia

In appropriately selected patients, PCA safely provides analgesia superior to that obtained with traditional IM prn opioid administration; however, to date, no compelling evidence shows that PCA is associated with a reduction in morbidity or a more rapid recovery. PCA is deceptively easy to prescribe; however, to use it effectively and safely requires experience, frequent patient assessment, and a skilled and knowledgeable nursing staff.

[Propacetamol: from basic action to clinical utilization]

OBJECTIVE

To review pharmacology and therapeutic use of propacetamol, an injectable prodrug of acetaminophen (paracetamol).

DATA SOURCES

Extraction from the Medline database of French and English articles on pharmacology and clinical use of propacetamol.

STUDY SELECTION

Articles providing new data into the mechanisms of the analgesic action of paracetamol. Selection of controlled studies (original articles and abstracts of oral communications on therapeutic trials with propacetamol as a single agent or part of balanced analgesia protocols). Case reports and letters to the editor were not considered in this analysis.

DATA EXTRACTION

Clinical articles were selected for advantages and adverse effects of propacetamol. Articles dealing with mechanisms of action of propacetamol and paracetamol were selected for the more recent data, excluding those reporting outdated theories not confirmed or abandoned.

DATA SYNTHESIS AND CONCLUSION

Mechanisms of action of paracetamol differ from those of NSAIDs, giving account of a low risk of adverse renal, gastrointestinal and haematological effects. Thanks to their high therapeutic index, prescription of propacetamol and paracetamol is quite simple and safe. Main indications of both drugs are painful conditions, especially but not exclusively in the postoperative period, not requiring opioids and also in combination with other analgesic drug and/or techniques (balanced or multimodal analgesia). Because of cost, IV propacetamol is changed for oral paracetamol as soon as possible.