Pharmacology of Acetaminophen, Nonsteroidal Antiinflammatory Drugs, and Steroid Medications: Implications for Anesthesia or Unique Associated Risks

Perioperative Pain Management for Distal Radius Fractures

Distal radius fractures have a high incidence among both young and elderly patients, and in many instances require operative intervention. When operative intervention is employed, adequate pain management is essential to decrease postoperative complications, such as chronic pain and disability, while minimizing the risk of prolonged opioid use and dependence. Strategies to optimize pain management include regional anesthesia, preoperative dosing of medication, multimodal regimens, long-acting selective opioids at the time of surgery, corticosteroids, and non-pharmacologic therapies.

Multimodal Analgesia

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

Efficacy and safety of intravenous acetaminophen (2 g/day) for reducing opioid consumption in Chinese adults after elective orthopedic surgery: A multicenter randomized controlled trial

Background: Acetaminophen is an important component of a multimodal analgesia strategy to reduce opioid consumption and pain intensity after an orthopedic surgery. The opioid-sparing efficacy of intravenous acetaminophen has been established at a daily dose of 4 g. However, it is still unclear for the daily dose of 2 g of acetaminophen, which is recommended by the China Food and Drug Administration Center for Drug Evaluation, in terms of its efficacy and safety.

Objectives: This study aimed to evaluate the efficacy and safety of intravenous acetaminophen at a daily dose of 2 g for reducing opioid consumption and pain intensity after orthopedic surgery.

Methods: In this multicenter, randomized, double-blind, placebo-controlled phase III trial, 235 patients who underwent orthopedic surgery were randomly assigned to receive intravenous acetaminophen 500 mg every 6 h or placebo. Postoperative morphine consumption, pain intensity at rest and during movement, and adverse events were analysed.

Results: For the mean (standard deviation) morphine consumption within 24 h after surgery, intravenous acetaminophen was superior to placebo both in the modified intention-to-treat analysis [8.7 (7.7) mg vs. 11.2 (9.2) mg] in the acetaminophen group and the placebo group, respectively. Difference in means: 2.5 mg; 95% confidence interval, 0.25 to 4.61; p = 0.030), and in the per-protocol analysis (8.3 (7.0) mg and 11.7 (9.9) mg in the acetaminophen group and the placebo group, respectively. Difference in means: 3.4 mg; 95% confidence interval: 1.05 to 5.77; p = 0.005). The two groups did not differ significantly in terms of pain intensity and adverse events.

Conclusion: Our results suggest that intravenous acetaminophen at a daily dose of 2 g can reduce morphine consumption by Chinese adults within the first 24 h after orthopedic surgery, but the extent of reduction is not clinically relevant.

Clinical Trial Registration: [ClinicalTrials.gov], identifier [NCT02811991].

Perioperative Pain Management for Elective Spine Surgery: Opioid Use and Multimodal Strategies

In recent years, physicians and institutions have come to recognize the increasing opioid epidemic in the United States, thus prompting a dramatic shift in opioid prescribing patterns. The lack of well-studied alternative treatment regimens has led to a substantial burden of opioid addiction in the United States. These forces have led to a huge economic burden on the country. The spine surgery population is particularly high risk for uncontrolled perioperative pain, because most patients experience chronic pain preoperatively and many patients continue to experience pain postoperatively. Overall, there is a large incentive to better understand comprehensive multimodal pain management regimens, particularly in the spine surgery patient population. The goal of this review is to explore trends in pain symptoms in spine surgery patients, overview the best practices in pain medications and management, and provide a concise multimodal and behavioral treatment algorithm for pain management, which has since been adopted by a high-volume tertiary academic medical center.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Texture Analysis of Dried Droplets for the Quality Control of Medicines

The quality control of medicines guarantees the effectiveness of treatments for diseases. We explore the use of texture analysis of patterns in dried droplets as a tool to readily detect both impurities and changes in drug concentration. Four types of medicines associated with different routes of administration were analyzed: Methotrexate, Ciprofloxacin, Clonazepam, and Budesonide. We use NaCl and a hot substrate at 63 ∘C to promote aggregate formation and to reduce droplet drying time. Depending on the medicine, optical microscopy reveals different complex aggregates such as circular to oval splatters, fern-like islands, crown shapes, crown needle-like and bump-like patterns as well as dendritic branched and star-like crystals. We use some physical features of the stains (as the stain diameter and superficial area) and gray level co-occurrence matrix (GLCM) to characterize patterns of dried droplets. Finally, we show that structural analysis of stains can achieve 95% accuracy in identifying medicines with 30% water dilution, while it achieves 99% accuracy in detecting drugs with 10% other substances.

An observational study to evaluate the prescription pattern of analgesics used in the perioperative period in a tertiary care hospital

Background and Aims:

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. There are limited observational prescription pattern studies of analgesics in perioperative period in tertiary care hospitals for which this study was carried out in orthopedic, general surgery, and plastic surgery departments. The primary aim was to study the prescription pattern of analgesics in the perioperative period with the secondary aim to study the specific use of opioids and pain relief using the Visual Analog Scale (VAS).

Methods:

A total of 250, 250, and 100 patients were taken from orthopedic, general surgery, and plastic surgery departments, respectively. The analgesics commonly used in preoperative, intraoperative, and postoperative period were observed. The use of opioids in the perioperative period, the number of fixed drug combinations used, the number of generic drug prescription, and pain relief postoperatively were also observed. The analysis was done using descriptive statistics.

Results:

Total analgesics prescribed were 1168, 117, and 369 in orthopedic, general surgery, and plastic surgery departments, respectively, and were maximum in the intraoperative period. Most commonly used analgesic in the preoperative and postoperative period was paracetamol and that in intraoperative period was fentanyl. Nonsteroidal anti-inflammatory drugs (NSAIDs) were mainly prescribed by the general surgery department in postoperative period. The amount of pain in postoperative period after treatment with analgesics was mild to moderate as per the VAS.

Conclusion:

This study revealed that in preoperative and postoperative period, the most common analgesic used is paracetamol. In the intraoperative period, maximum patients received fentanyl. Diclofenac is an established NSAID used in the management of acute and chronic pain states. In our study, we found that the usage of paracetamol was more than NSAIDs and the usage of opioid was maximum during intraoperative period.

All about pain pharmacology: what pain physicians should know

From the perspective of the definition of pain, pain can be divided into emotional and sensory components, which originate from potential and actual tissue damage, respectively. The pharmacologic treatment of the emotional pain component includes antianxiety drugs, antidepressants, and antipsychotics. The anti-anxiety drugs have anti-anxious, sedative, and somnolent effects. The antipsychotics are effective in patients with positive symptoms of psychosis. On the other hand, the sensory pain component can be divided into nociceptive and neuropathic pain. Non-steroidal anti-inflammatory drugs (NSAIDs) and opioids are usually applied for somatic and visceral nociceptive pain, respectively; anticonvulsants and antidepressants are administered for the treatment of neuropathic pain with positive and negative symptoms, respectively. The NSAIDs, which inhibit the cyclo-oxygenase pathway, exhibit anti-inflammatory, antipyretic, and analgesic effects; however, they have a therapeutic ceiling. The adverse reactions (ADRs) of the NSAIDs include gastrointestinal problems, generalized edema, and increased bleeding tendency. The opioids, which bind to the opioid receptors, present an analgesic effect only, without anti-inflammatory, antipyretic, or ceiling effects. The ADRs of the opioids start from itching and nausea/vomiting to cardiovascular and respiratory depression, as well as constipation. The anticonvulsants include carbamazepine, related to sodium channel blockade, and gabapentin and pregabalin, related to calcium blockade. The antidepressants show their analgesic actions mainly through inhibiting the reuptake of serotonin or norepinephrine. Most drugs, except NSAIDs, need an up-dose titration period. The principle of polypharmacy for analgesia in case of mixed components of pain is increasing therapeutic effects while reducing ADRs, based on the origin of the pain.

Systemic adjunct analgesics for cesarean delivery: a narrative review

It is critical to adequately treat postoperative cesarean delivery pain. The use of parenteral or neuraxial opioids has been a mainstay, but opioids have side effects that can be troubling and the opioid crisis in the United States has highlighted the necessity to utilize analgesics other than opioids. Other analgesic options include neuraxial analgesics, nerve blocks such as the transversus abdominis plane block, and non-opioid parenteral and oral medications. The goal of this article is to review non-opioid systemic analgesic adjuncts following cesarean delivery, focusing on their efficacy and side effects as well as their impact on reduction of opioid requirements after surgery.

Premedication with oral paracetamol for reduction of propofol injection pain: a randomized placebo-controlled trial

Background

To compare the effect of premedication with 2 different doses of oral paracetamol to prevent pain at propofol intravenous injection.

Methods

We conducted a double-blind randomized controlled trial in which patients scheduled for induction of general anesthesia with intravenous propofol received either a placebo, 500 mg or 1000 mg of oral paracetamol (P500 and P1000, respectively) 1 h prior to induction. Two mg/kg of propofol was injected at a rate of 600 ml/hr. After 1/4 of the full dose had been injected, the syringe pump was paused, and patients were asked to rate pain at the injection site using a verbal numerical rating score (VNRS) from 0 to 10.

Results

Three hundred and twenty-four patients were included. Pain intensity was lower in both P500 and P1000 groups (median VNRS [interquartile range] = 2 [0–3] and 4 [2–5], respectively) than in the placebo group (8 [7–10]; P < 0.001)*. The rate of pain was lower in the P1000 group (70.4%) than in both the P500 and the placebo group (86.1 and 99.1%, respectively; P < 0.001)*. The respective rates of mild (VNRS 1–3), moderate (VNRS 4–6) and severe pain (VNRS 7–10) were 47.2, 23.2 and 0% in the P1000 group, 28.7, 50 and 7.4% in the P500 group, and 0, 22.2 and 76.9% in the placebo group (P < 0.001* for between group comparisons). Tolerance was similar in the 3 groups.

Conclusions

A premedication with oral paracetamol can dose-dependently reduce pain at propofol intravenous injection. To avoid this common uncomfortable concern for the patients, this well-tolerated, available and cheap treatment appears as an option to be implemented in the current practice.

Trial registration

TCTR20150224002. Prospectively registered on 24 February 2015.

Evaluating the Effect of Intravenous Acetaminophen in Multimodal Analgesia After Total Hip Arthroplasty: A Randomized Controlled Trial

BACKGROUND

Postoperative pain is a significant concern of patients before surgery. Multimodal pain management is an effective method of pain control after major orthopedic surgery. Acetaminophen is the most commonly used analgesic for the management of pain. It was hypothesized that 1000 mg of intravenous acetaminophen (IA) dosed every 6 hours would significantly reduce the postoperative pain score at rest and the opioid consumption volume in patients who would undergo total hip arthroplasty (THA) when compared to a control group.

METHODS

A single-center, prospective, open-label randomized control study was conducted. A total of 97 patients undergoing unilateral primary THA were divided into 2 groups: the study group (IA) (n = 45) and the control group (n = 52). The study group received administered IA after surgery, while the control group received only a standard pain control. Both groups received a preoperative femoral nerve block and postoperative intravenous fentanyl citrate. The primary outcome was the evaluation of the pain score at rest 24 hours after surgery. The pain score was measured using the Numerical Rating Scale. The primary outcome of this study was analyzed using generalized estimating equation.

RESULTS

The IA group had a significant improvement in Numerical Rating Scale score at rest 24 hours after THA compared to the control group (-0.91, 95% confidence interval -1.56 to -0.26, P = .006), suggesting a positive effect of IA usage for pain relief. The total fentanyl citrate consumption after surgery for 24 hours was significantly lower in the IA group than those of the control group (52.07 ± 7.64 vs 57.83 ± 12.44 mg, P < .001).

CONCLUSION

Postoperative administration of IA significantly reduced the postoperative pain score and opioid consumption volume after primary THA. IA was useful as one role of multimodal pain management after THA.

LEVEL OF EVIDENCE

Level 2.

Performance evaluation of five commercial assays for detection of acetaminophen

BACKGROUND

To evaluate the analytical performance of five commercial acetaminophen assays and select the best method for routine use.

METHODS

Imprecision, accuracy, linearity, and interferences of three enzymatic assays (Beckman Coulter AU Paracetamol, Abbott MULTIGENT Acetaminophen, and Sekisui Acetaminophen L3K) and two immunoassay-based assays (Beckman Coulter SYNCHRON ACTM (Acetaminophen) Reagent and Siemens SYVA Emit-tox Acetaminophen) were evaluated on a Beckman Coulter AU680 chemistry analyzer. Hook effect for immunoassay-based assays and recovery in ultrafiltrate for enzymatic methods were studied.

RESULTS

Within-run and between-run imprecision of the enzymatic assays ranged 0.26%-0.82% and 0.53%-2.86%, respectively, while that for the immunoassay-based methods ranged 0.96%-6.34% and 1.50%-11.33%, respectively. All assays except the SYNCHRON assay fell within the program analytical performance specifications (±20 µmol/L or 10%) for external quality assurance (EQA) samples, with the highest positive bias (31.7%) observed in the SYNCHRON assay. Icteric interference was demonstrated most significantly in the Abbott assay (up to 88 μmol/L positive bias in blank serum). The lipemic interference on the SYNCHRON was significant (up to 110% positive bias at level of 100 μmol/L). The immunoassay-based methods were less susceptible to hemolytic interference, while the Abbott and AU assays were more susceptible to N-acetylcysteine interference. Both immunoassay-based methods showed no hook effect up to 18 000 μmol/L. Ultrafiltration recoveries for enzymatic methods were satisfactory, ranging from 80.0% ± 5.1% to 89.5% ± 3.0%.

CONCLUSIONS

Proportional bias was observed in the SYNCHRON assay, while the Siemens and Sekisui assays were minimally affected by bilirubin interferences.

Comparison of intravenous and oral acetaminophen for pain control after total knee and hip arthroplasty: A systematic review and meta-analysis

OBJECTIVE

To evaluate the efficacy between intravenous and oral acetaminophen as adjunct to multimodal analgesia regimens for pain management after total knee and hip arthroplasties.

METHODS

We conduct electronic searches of Medline (1966-2017.09), PubMed (1966-2017.09), Embase (1980-2017.09), ScienceDirect (1985-2017.09), and the Cochrane Library. Only randomized controlled trials (RCTs) are included. The quality assessment is performed according to the Cochrane systematic review method. Fixed/random effect model is adopted according to the heterogeneity tested by I statistic. Meta-analysis is performed using Stata 11.0 software.

RESULTS

Two RCTs are included involving 236 patients. The present meta-analysis demonstrated that there were no significant differences between groups regarding pain scores at 12, 24, or 48 hours. No significant differences were observed in terms of opioid consumption at 12, 24, or 48 hours after arthroplasties.

CONCLUSION

Intravenous acetaminophen to multimodal analgesia dose not demonstrate a significant benefit in reducing pain and opioid consumption compared oral formulation after total knee arthroplasty and total hip arthroplasty. Higher-quality RCTs are required for further research.

Basic/Translational Development of Forthcoming Opioid- and Nonopioid-Targeted Pain Therapeutics

Opioids represent an efficacious therapeutic modality for some, but not all pain states. Singular reliance on opioid therapy for pain management has limitations, and abuse potential has deleterious consequences for patient and society. Our understanding of pain biology has yielded insights and opportunities for alternatives to conventional opioid agonists. The aim is to have efficacious therapies, with acceptable side effect profiles and minimal abuse potential, which is to say an absence of reinforcing activity in the absence of a pain state. The present work provides a nonexclusive overview of current drug targets and potential future directions of research and development. We discuss channel activators and blockers, including sodium channel blockers, potassium channel activators, and calcium channel blockers; glutamate receptor-targeted agents, including N-methyl-D-aspartate, α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, and metabotropic receptors. Furthermore, we discuss therapeutics targeted at γ-aminobutyric acid, α2-adrenergic, and opioid receptors. We also considered antagonists of angiotensin 2 and Toll receptors and agonists/antagonists of adenosine, purine receptors, and cannabinoids. Novel targets considered are those focusing on lipid mediators and anti-inflammatory cytokines. Of interest is development of novel targeting strategies, which produce long-term alterations in pain signaling, including viral transfection and toxins. We consider issues in the development of druggable molecules, including preclinical screening. While there are examples of successful translation, mechanistically promising preclinical candidates may unexpectedly fail during clinical trials because the preclinical models may not recapitulate the particular human pain condition being addressed. Molecular target characterization can diminish the disconnect between preclinical and humans' targets, which should assist in developing nonaddictive analgesics.