Drug combinations in pain treatment: a review of the published evidence and a method for finding the optimal combination

Cannabinoid Analgesia in Postoperative Pain Management: From Molecular Mechanisms to Clinical Reality

Postoperative pain (POP) is a challenging clinical phenomenon that affects the majority of surgical patients and demands effective management to mitigate adverse outcomes such as persistent pain. The primary goal of POP management is to alleviate suffering and facilitate a seamless return to normal function for the patient. Despite compelling evidence of its drawbacks, opioid analgesia remains the basis of POP treatment. Novel therapeutic approaches rely on multimodal analgesia, integrating different pharmacological strategies to optimize efficacy while minimizing adverse effects. The recognition of the imperative role of the endocannabinoid system in pain regulation has prompted the investigation of cannabinoid compounds as a new therapeutic avenue. Cannabinoids may serve as adjuvants, enhancing the analgesic effects of other drugs and potentially replacing or at least reducing the dependence on other long-term analgesics in pain management. This narrative review succinctly summarizes pertinent information on the molecular mechanisms, clinical therapeutic benefits, and considerations associated with the plausible use of various cannabinoid compounds in treating POP. According to the available evidence, cannabinoid compounds modulate specific molecular mechanisms intimately involved in POP. However, only two of the eleven clinical trials that evaluated the efficacy of different cannabinoid interventions showed positive results.

The effect of risperidone on behavioral reactions and gene expression of pro- and anti-inflammatory cytokines in neuropathic pain model induced by chronic constriction injury of the sciatic nerve in rat

BACKGROUND

Neuropathic pain results from lesions or diseases affecting the somatosensory system. The management of a patient with chronic neuropathic pain remains a challenge several studies report the analgesic effect of serotonin receptor antagonists in different models of experimental pain. The present study was designed to study the effect of systemic administration of risperidone, on behavioral scores of neuropathic pains in chronic constriction (CCI) model in rats.

METHODS

Inducing neuropathic pain with the CCI model which causes heat hyperalgesia, heat, and mechanical allodynia was performed on rats, and then, in two phases, risperidone effect was determined. In the acute phase, risperidone 1, 2, 4 mg was administered for three groups half an hour before behavioral tests on the 7th, 14th, and 21st day after surgery, and in the chronic phase, risperidone 1, 2, and 4 mg was administered for three different groups from the 1st to 14th days after surgery than on 14th-day behavioral scores were performed. For gene expression analysis, samples are taken from spinal cord tissues in lumbar segments.

RESULTS

This study shows chronic administration of risperidone as an antipsychotic drug was effective on heat hyperalgesia and allodynia. However, only the max dosage (4 mg) of risperidone showed meaningful improvement in increasing mechanical allodynia. However, acute administering of risperidone did not show any meaningful changes in behavioral tests on neuropathic pain induced by chronic constriction injury of the sciatic nerve in rats. In addition, gene expression results showed an increase in IL-4 and IL-10 gene expression in the risperidone group compared to the sham group.

CONCLUSION

This study suggests the helpful preventive effects of risperidone in developing and increasing neuropathic pain, but it does not have any instant effect.

Antinociceptive and anti-inflammatory activity of DW-1021, the ionic complex of pelubiprofen and tramadol, in rodents

Although drugs such as acetaminophen, opioids, and nonsteroidal anti-inflammatory drugs (NSAIDs), are commonly used for pain management, the side effects of these drugs such as hepatotoxicity, nephrotoxicity, nausea, and vomiting, can not be neglected. Therefore, combinations of analgesics with different mechanisms raise the possibility of developing novel analgesics. Therefore, the aim of the present study was to evaluate whether DW-1021, the ionic complex of pelubiprofen (NSAID) and tramadol (opioid), has synergic antinociceptive and anti-inflammatory effects in nociceptive as well as inflammation-induced nociceptive models compared to pelubiprofen- or tramadol-only administration. Strong synergistic antinociceptive efficacy of DW-1021 was observed in the mouse writhing test and von Frey paw withdrawal threshold test in the carrageenan-induced rats. The hot plate test in mice and the Randall-Selitto mechanical paw pressure test in carrageenan-induced rats revealed that DW-1021 had a preferable effect on relieving pain to pelubiprofen, but not as much as tramadol. In the carrageenan-induced rats, DW-1021 had a more potent effect on reducing paw inflammation (paw volume, width, and thickness) via the suppression of PGE₂ production than tramadol, but less than that of pelubiprofen. Taken together, our results suggest that the administration of DW-1021, a combination of pelubiprofen and tramadol, exerted a potent effect and can be used as a potential therapeutic agent for relieving pain and inflammation.

Application of sequential multimodal analgesia before and after impacted mandibular third molar extraction: Protocol for a randomized controlled trial

Background

Several analgesics have been applied under various protocols to control the moderate-to-severe postoperative pain caused by the surgical extraction of an impacted mandibular third molar. However, a consensus on optimal pain management while minimizing side effects is yet to be reached.

Methods

This multi-center, prospective, double-blind, randomized controlled trial aims to evaluate the efficacy and safety of sequential multimodal analgesia combined with postoperative zaltoprofen along with multiple preemptive analgesics. A total of 80 participants with bilateral impacted mandibular third molar from two hospitals were randomized into two groups. Two surgical extractions were performed at one-month intervals, and in a crossover design, celecoxib or tramadol/acetaminophen was administered before one extraction and placebo before the other extraction. Following extraction, all subjects took zaltoprofen for 5 days. The outcome measures included pain at specific times, time and intensity of the first pain onset after extraction, need of rescue drugs, and occurrence and frequency of side effects.

Conclusions

This ongoing clinical trial was designed to provide evidence regarding a new protocol for effective postoperative pain management of a commonly performed surgical extraction. The results of this study will provide guidance to clinicians regarding the timing and combination of oral analgesics in various oral surgeries performed under local anesthesia.

Trial registration

KCT0005450, registered on October 7, 2020.

Co-administration of Pregabalin and Curcumin Synergistically Decreases Pain-Like Behaviors in Acute Nociceptive Pain Murine Models

Analgesic drugs in a combination-form can achieve greater efficacy with lesser side effects compared to either drug alone. The combination of drugs acting at different targets or mechanisms of action has been recognized as an alternative approach for achieving optimal analgesia. In this study, the analgesic effects of pregabalin (30, 60, 100, 200 mg/kg), curcumin (15, 30, 60, 100, 120 mg/kg), and 1:1 fixed-dose ratio of the pregabalin-curcumin combination were assessed using two acute nociceptive pain models, the acetic acid-induced writhing and tail-flick tests in mice. The pregabalin-curcumin combination produced a dose-dependent decrease in mean of writhes and an increase in the percentage of antinociception by the acetic acid-induced writhing test. In the tail-flick test, the combination also showed an improvement in antinociception indicated by the tail-flick latency, % antinociception, and area under the curve (AUC). Isobolographic analysis of interactions demonstrated a significant synergistic interaction effect between pregabalin and curcumin in both acute nociceptive pain models with the experimental ED₅₀ below the predicted additive line and the combination index < 1. These findings demonstrate that the combination of pregabalin and curcumin exhibits a synergistic interaction in mouse models of acute nociceptive pain.

A Randomized Controlled Trial of Enhanced Recovery After Surgery Versus Standard of Care Recovery for Emergency Cesarean Deliveries at Mbarara Hospital, Uganda

BACKGROUND

Enhanced recovery after surgery (ERAS) expedites return to patient baseline and functional status by reducing surgical trauma, stress, and organ dysfunction. Despite the potential benefits of enhanced recovery protocols, limited research has been done in low-resource settings, where 95% of cesarean deliveries are emergent and could possibly benefit from the application of ERAS protocols.

METHODS

In a prospective, randomized, single-blind, controlled trial, mothers delivering by emergency cesarean delivery were randomly assigned to either an ERAS or a standard of care (SOC) recovery arm. Patients in the ERAS arm were treated with a modified ERAS protocol that included modified counseling and education, prophylactic antibiotics, antiemetics, normothermia, restrictive fluid administration, and multimodal analgesia. They also received early initiation of mobilization, feeding, and urethral catheter removal. The primary end point was length of hospital stay. The secondary end points were complications and readmission rates. Mean length of stay in the intervention and control arms were compared using t tests. Statistical analyses were performed using STATA version 13 (College Station, TX).

RESULTS

A total of 160 patients were enrolled in the study, with 80 randomized to each arm. There was a statistically significant shorter length of stay for the ERAS arm compared to SOC, with a difference of -18.5 hours (P < .001, 95% confidence interval [CI], -23.67, -13.34). The incidence of complications of severe pain and headache was lower in the ERAS arm compared to SOC (P = .001 for both complications). However, pruritus was more common in the ERAS arm compared to SOC (P = .023).

CONCLUSIONS

Use of an ERAS protocol for women undergoing emergency cesarean delivery in a low-income setting is feasible and reduces length of hospital stay without generally increasing the complication rate.

Multimodal Pain Management and Postoperative Outcomes in Lumbar Spine Fusion Surgery: A Population-based Cohort Study

STUDY DESIGN

Retrospective population-based cohort analysis.

OBJECTIVE

Given the lack of large-scale data on the use and efficacy of multimodal analgesia in spine fusion surgery, we conducted a population-based analysis utilizing the nationwide claims-based Premier Healthcare database.

SUMMARY OF BACKGROUND DATA

Multimodal analgesia, combining different pain signaling pathways to achieve additive and synergistic effects, is increasingly emerging as the standard of care.

METHODS

Cases of posterior lumbar fusion surgery were extracted (2006-2016). Opioid-only analgesia was compared to multimodal analgesia, that is, systemic opioid analgesia + either acetaminophen, steroids, gabapentinoids, ketamine, nonsteroidal anti-inflammatory drugs (NSAIDs), cyclooxygenase-2 (COX-2) inhibitors, or neuraxial anesthesia (categorized into 1, 2, or >2 additional analgesic modes). Mixed-effects models measured associations between multimodal analgesia categories and outcomes, including opioid prescription dose, cost/length of hospitalization, and opioid-related complications. Odds ratios (ORs, or % change) and 95% confidence intervals (CIs) are reported.

RESULTS

Among 265,538 patients the incidence of multimodal analgesia was 61.1% (162,156); multimodal pain management-specifically when adding NSAIDs/COX-2 inhibitors to opioids-was associated with reduced opioid prescription (-13.3% CI -16.7 to -9.7%), cost (-2.9% CI -3.9 to -1.8%) and length of hospitalization (-7.3% CI -8.5 to -6.1%). Multimodal analgesia in general was associated with stepwise decreased odds for gastrointestinal complications (OR 0.95, 95% CI 0.88-1.04; OR 0.84, CI 0.75-0.95; OR 0.78, 95% CI 0.64-0.96), whereas odds were increased for postoperative delirium (OR 1.14, 95% CI 1.00-1.32; OR 1.33, 95% CI 1.11-1.59; OR 1.31, 95% CI 0.99-1.74), and counterintuitively- naloxone administration (OR 1.25, 95% CI 1.13-1.38; OR 1.56, 95% CI 1.37-1.77; OR 1.84, 95% CI 1.52-2.23) with increasing analgesic modes used: one, two, or more additional analgesic modes, respectively. Post-hoc analysis revealed that specifically gabapentinoid use increased odds of naloxone requirement by about 50%, regardless of concurrent opioid dose (P < 0.001).

CONCLUSION

Although multimodal analgesia was not consistently implemented in spine fusion surgery, particularly NSAIDs and COX-2 inhibitors demonstrated opioid sparing effects. Moreover, results suggest a synergistic interaction between gabapentinoids and opioids, the former potentiating opioid effects resulting in greater naloxone requirement.

LEVEL OF EVIDENCE

3.

Release Adjustment of Two Drugs with Different Solubility Combined in a Matrix Tablet

The objective of this study was to modify the release of two drugs having different solubility in a combined matrix tablet as a fixed-dose combination for extended release. Propranolol HCl (freely soluble) and carbamazepine (very slightly soluble) were used as model drugs, water-soluble hydroxypropyl methylcellulose (HPMC) and water-insoluble ethylcellulose (EC) were used as matrix-forming polymers. Tablets were prepared by direct compression of powder blends, or propranolol HCl was first granulated with one of the matrix-forming polymers (1:1) followed by compression with carbamazepine and matrix former. Propranolol HCl release from directly compressed tablets was faster than carbamazepine because of its higher solubility. The release of both drugs was fast when HPMC-propranolol HCl granules were compressed with carbamazepine into EC matrix tablet. Conversely, the release of both drugs was decreased when HPMC-propranolol HCl granules and carbamazepine were compressed into HPMC matrices. The desired release of both drugs was approached when EC-propranolol HCl granules were compressed with carbamazepine into HPMC matrix. Erosion of the HPMC matrix and, therefore, drug release were adjusted by varying the molecular weight of HPMC. A burst release of propranolol HCl decreased when it was granulated with EC in a fluidized bed coater followed by compression with carbamazepine into HPMC matrix.

Pain in Urology: Pathophysiological Aspects of Pain and Chronicity

Chronic pain has been traditionally defined by pain duration, but this approach has limited empirical support and does not account for chronic pain multidimensionality. Defining chronic pain solely by duration is based on the view that acute pain signals potential tissue damage, whereas chronic pain results from central sensitization in which pain is sustained after nociceptive inputs have diminished. Chronic urological pain is a prevalent condition, which can represent a major challenge to health care providers due to its complex aetiology and poor response to therapy. In most cases, clear signs of on-going tissue trauma, inflammation or infection are not present. Despite this, more underhanded pathophysiological mechanisms, affecting the urinary system or other pelvic organ systems (musculoskeletal, neurologic, urologic, gynaecologic) and some psychological aspects may be present. In this article, some pathophysiological aspects of visceral pain are discussed; the definition of ‘chronic pain’, the mechanism of action of drugs used in the treatment of pain and the rationale for association therapy are also reviewed.

Ultra-Low Doses of Naltrexone Enhance the Antiallodynic Effect of Pregabalin or Gabapentin in Neuropathic Rats

Preclinical Research Treatment of neuropathic pain is an area of largely unmet medical need. Pregabalin and gabapentin are anticonvulsants widely used for the treatment of neuropathic pain. Unfortunately, these drugs are only effective in 50-60% of the treated patients. In addition, both drugs have substantial side effects. Several studies have reported that ultralow doses of opioid receptor antagonists can induce analgesia and enhance the analgesic effect of opioids in rodents and humans. The objective of the present study was to assess the antiallodynic synergistic interaction between gabapentinoids and naltrexone in rats. Oral administration of pregabalin (ED₅₀  = 2.79 ± 0.16 mg/kg) or gabapentin (ED₅₀  = 21.04 ± 2.87 mg/kg) as well as intrathecal naltrexone (ED₅₀  = 0.11 ± 0.02 ng) reduced in a dose-dependent manner tactile allodynia in rats. Maximal antiallodynic effects (∼100%) were reached with 30 mg/kg of pregabalin, 300 mg/kg of gabapentin or 0.5 ng of naltrexone. Co-administration of pregabalin or gabapentin and naltrexone in a fixed-dose ratio (1:1) remarkably reduced spinal nerve ligation-induced tactile allodynia showing a synergistic interaction. The data indicate that combinations of pregabalin or gabapentin and ultra-low doses of naltrexone are able to reduce tactile allodynia in neuropathic rats with lower doses that those used when drugs are given individually and with an improved side effects profile. Drug Dev Res 78 : 371-380, 2017. © 2017 Wiley Periodicals, Inc.

Current Trends in Multidrug Optimization: An Alley of Future Successful Treatment of Complex Disorders

The identification of effective and long-lasting cancer therapies still remains elusive, partially due to patient and tumor heterogeneity, acquired drug resistance, and single-drug dose-limiting toxicities. The use of drug combinations may help to overcome some limitations of current cancer therapies by challenging the robustness and redundancy of biological processes. However, effective drug combination optimization requires the careful consideration of numerous parameters. The complexity of this optimization problem is clearly nontrivial and likely requires the assistance of advanced heuristic optimization techniques. In the current review, we discuss the application of optimization techniques for the identification of optimal drug combinations. More specifically, we focus on the application of phenotype-based screening approaches in the field of cancer therapy. These methods are divided into three categories: (1) modeling methods, (2) model-free approaches based on biological search algorithms, and (3) merged approaches, particularly phenotypically driven network biology methods and computation network models relying on phenotypic data. In addition to a brief description of each approach, we include a critical discussion of the advantages and disadvantages of each method, with a strong focus on the limitations and considerations needed to successfully apply such methods in biological research.

Current Trends in Multidrug Optimization

The identification of effective and long-lasting cancer therapies still remains elusive, partially due to patient and tumor heterogeneity, acquired drug resistance, and single-drug dose-limiting toxicities. The use of drug combinations may help to overcome some limitations of current cancer therapies by challenging the robustness and redundancy of biological processes. However, effective drug combination optimization requires the careful consideration of numerous parameters. The complexity of this optimization problem is clearly nontrivial and likely requires the assistance of advanced heuristic optimization techniques. In the current review, we discuss the application of optimization techniques for the identification of optimal drug combinations. More specifically, we focus on the application of phenotype-based screening approaches in the field of cancer therapy. These methods are divided into three categories: (1) modeling methods, (2) model-free approaches based on biological search algorithms, and (3) merged approaches, particularly phenotypically driven network biology methods and computation network models relying on phenotypic data. In addition to a brief description of each approach, we include a critical discussion of the advantages and disadvantages of each method, with a strong focus on the limitations and considerations needed to successfully apply such methods in biological research.

Variations in the Use of Perioperative Multimodal Analgesic Therapy

BACKGROUND

Practice guidelines for perioperative pain management recommend that multimodal analgesic therapy should be used for all postsurgical patients. However, the proportion of patients who actually receive this evidence-based approach is unknown. The objective of this study was to describe hospital-level patterns in the utilization of perioperative multimodal analgesia.

METHODS

Data for the study were obtained from the Premier Research Database. Patients undergoing below-knee amputation, open lobectomy, total knee arthroplasty, and open colectomy between 2007 and 2014 were included in the analysis. Patients were considered to have multimodal therapy if they received one or more nonopioid analgesic therapies. Mixed-effects logistic regression models were used to estimate the hospital-specific frequency of multimodal therapy use while adjusting for the case mix of patients and hospital characteristics and accounting for random variation.

RESULTS

The cohort consisted of 799,449 patients who underwent a procedure at 1 of 315 hospitals. The mean probability of receiving multimodal therapy was 90.4%, with 95% of the hospitals having a predicted probability between 42.6 and 99.2%. A secondary analysis examined whether patients received two or more nonopioid analgesics, which gave an average predicted probability of 54.2%, with 95% of the hospitals having a predicted probability between 9.3 and 93.2%.

CONCLUSIONS

In this large nationwide sample of surgical admissions in the United States, the authors observed tremendous variation in the utilization of multimodal therapy not accounted for by patient or hospital characteristics. Efforts should be made to identify why there are variations in the use of multimodal analgesic therapy and to promote its adoption in appropriate patients.

Comparison between paracetamol, piroxicam, their combination, and placebo in postoperative pain management of upper limb orthopedic surgery (a randomized double blind clinical trial)

Background:

Therapeutic superiority of a combination of Paracetamol and nonsteroidal anti-inflammatory drugs (NSAIDs) over either drug alone remains controversial. We evaluated the efficiency of a combination of Paracetamol and Piroxicam versus each drug alone and also placebo in the management of postoperative pain, in patients who had undergone elective upper limb orthopedic surgery under general anesthesia.

Materials and Methods:

A total of 100 patients were randomly divided into four groups to receive either intravenous (IV) infusion of Paracetamol, 15 mg/kg., intramuscular (IM) injection of Piroxicam 0.4 mg/kg., their combination or placebo. The pain scores were recorded at the first; second, fourth, sixth, twelfth, and 24 hours after Post Anesthesia Care Unit (PACU) admission. After the operation 0.1 mg/kg of morphine was administered, if the patient needed.

Result:

The means of the pain scores were 5.26 ± 1.53, 4.09 ± 0.88, 4.36 ± 1.48, and 4.11 ± 1.29, in groups A, B, C, and D, respectively, (Group A: received placebo; Group B: received both Paracetamol and Piroxicam; Group C received Piroxicam; Group D received Paracetamol). Except for differences between the mean pain scores in Groups B and D, the other differences were statistically significant (P value < 0.05). No adverse effect was reported in the four groups.

Conclusion:

IV infusion of 15 mg/kg Paracetamol used as a preventive may provide effective analgesia in comparison with IM 0.4 mg/kg Piroxicam or placebo. Addition of Piroxicam to Paracetamol has not much more benefit than Paracetamol alone, in reducing pain after upper limb orthopedic surgery.

Randomized clinical trial of dexketoprofen/tramadol 25 mg/75 mg in moderate-to-severe pain after total hip arthroplasty

Background. The aim was to evaluate the analgesic efficacy and safety of the dexketoprofen/tramadol 25 mg/75 mg fixed-dose combination vs dexketoprofen (25 mg) and tramadol (100 mg) in moderate-to-severe acute pain after total hip arthroplasty.

Methods. This was a randomized, double-blind, parallel-group study in patients experiencing pain of at least moderate intensity on the day after surgery, compared with placebo at first administration to validate the pain model. The study drug was administered orally every 8 h throughout a 5 day period. Rescue medication, metamizole 500 mg, was available during the treatment period. The evaluation of efficacy was based on patient assessments of pain intensity and pain relief. The primary end point was the mean sum of the pain intensity difference values throughout the first 8 h (SPID₈).

Results. Overall, 641 patients, mean age 62 (range 29–80) yr, were analysed; mean (sd) values of SPID₈ were 247 (157) for dexketoprofen/tramadol, 209 (155) for dexketoprofen, 205 (146) for tramadol, and 151 (159) for placebo. The primary analysis confirmed the superiority of the combination over dexketoprofen 25 mg (P=0.019; 95% confidence interval 6.4–73) and tramadol 100 mg (P=0.012; 95% confidence interval 9.5–76). The single components were superior to placebo (P<0.05), confirming model sensitivity. Most secondary analyses supported the superiority of the combination. The incidence of adverse drug reactions was low and similar among active treatment groups.

Conclusion. The efficacy results confirmed the superiority of dexketoprofen/tramadol over its single components, even at higher doses (tramadol), with a safety profile fully in line with that previously known for these agents in monotherapy.

Clinical trial registration. EudraCT 2012-004548-31 (https://www.clinicaltrialsregister.eu/ctr-search/search?query=eudract_number:2012-004548-31);

ClinicalTrials.gov NCT01902134 (https://www.clinicaltrials.gov/ct2/show/NCT01902134?term=NCT01902134&rank=1).

The Efficacy and Clinical Safety of Various Analgesic Combinations for Post-Operative Pain after Third Molar Surgery: A Systematic Review and Meta-Analysis

OBJECTIVES

To run a systematic review and meta-analysis of randomized clinical trials aiming to answer the clinical question "which analgesic combination and dosage is potentially the most effective and safe for acute post-operative pain control after third molar surgery?".

MATERIALS AND METHODS

A systematic search of computer databases and journals was performed. The search and the evaluations of articles were performed by 2 independent reviewers in 3 rounds. Randomized clinical trials related to analgesic combinations for acute post-operative pain control after lower third molar surgery that matched the selection criteria were evaluated to enter in the final review.

RESULTS

Fourteen studies with 3521 subjects, with 10 groups (17 dosages) of analgesic combinations were included in the final review. The analgesic efficacy were presented by the objective pain measurements including sum of pain intensity at 6 hours (SPID6) and total pain relief at 6 hours (TOTPAR6). The SPID6 scores and TOTPAR6 scores of the reported analgesic combinations were ranged from 1.46 to 6.44 and 3.24 - 10.3, respectively. Ibuprofen 400mg with oxycodone HCL 5mg had superior efficacy (SPID6: 6.44, TOTPAR6: 9.31). Nausea was the most common adverse effect, with prevalence ranging from 0-55%. Ibuprofen 200mg with caffeine 100mg or 200mg had a reasonable analgesic effect with fewer side effects.

CONCLUSION

This systematic review and meta-analysis may help clinicians in their choices of prescribing an analgesic combination for acute post-operative pain control after lower third molar surgery. It was found in this systematic review Ibuprofen 400mg combined with oxycodone HCL 5mg has superior analgesic efficacy when compared to the other analgesic combinations included in this study.

Involvement of nitric oxide and ATP-sensitive potassium channels in the peripheral antinoceptive action of a tramadol-dexketoprofen combination in the formalin test

Systemic coadministration of tramadol and dexketoprofen can produce antinociceptive synergism in animals. There has been only limited evaluation of this drug combination in the peripheral nervous system in terms of the antinociceptive interaction and its mechanisms. The aim of the present study was to evaluate the peripheral antinociceptive interaction between tramadol and dexketoprofen in the formalin test and the involvement of the nitric oxide (NO)-cyclic guanosine monophosphate pathway and ATP-sensitive K(+) channels. Different doses of tramadol or dexketoprofen were administered locally to the formalin-injured mouse paw and the antinociceptive effect evaluated. ED50 values were calculated for both drugs alone and in combination. Coadministration of tramadol and dexketoprofen produced an antinociceptive synergistic interaction during the second phase of the formalin test. Pretreatment with NO antagonists, including l-NG-nitroarginine methyl ester and 1H-[1,2,4]-oxadiazolo-[4,3-a]-quinoxalin-1-one, or the ATP-sensitive K(+) channel antagonist glibenclamide reversed the antinociceptive synergistic effect of the tramadol-dexketoprofen combination, suggesting that NO and ATP-sensitive K(+) channels were involved.

Peripheral synergism between tramadol and ibuprofen in the formalin test

Preclinical Research Analgesics with different mechanisms of action can be combined in order to obtain pharmacological synergism, employing lower doses of each agent, thus diminishing side effects. For instance, an atypical dual analgesic such as tramadol (TMD) and a nonsteroidal anti-inflammatory drug such as ibuprofen (IBU) are good candidates to be evaluated when combined and applied peripherally. The present study was conducted to evaluate possible local synergism between TMD and IBU when combined peripherally using the formalin test in rats. The effects of the individual analgesics and their combinations were evaluated simultaneously using a 5% formalin dilution. Dose-effect curves were determined for TMD (50-400 μg/paw) and IBU (1-100 μg/paw). Experimental effective doses were evaluated and isobolographic analyses were constructed to evaluate TMD-IBU combination synergism. Both drugs produced a dose-dependent analgesic effect when applied separately. Isobolographic analysis showed synergism during phase 1 (0-10 min) and phase 2 (15-60 min) when compared with theoretical doses (P < 0.05), with interaction indexes of 0.06 and 0.09, respectively. The present information supports the peripheral analgesic effect of TMD and IBU, especially when combined at appropriate doses.

Synergism between fentanyl and tramadol in tonic inflammatory pain: the orofacial formalin test

Opioids have been used for long time to management of pain, the coadministration of two opioids may induce synergism. The present study was conducted to determine the antinociceptive interaction between the dual mechanism of action of tramadol compared to the main of fentanyl antinociception in the orofacial formalin which represents a model of persistent cutaneous nociception in the region innervated by the trigeminal nerve. The i.p. administration of tramadol and fentanyl induced a dose-dependent antinociception with an ED(50) of 2.97 ± 0.32 mg/kg for phase I and 1.79 ± 0.30 mg/kg for phase II and 0.062 ± 0.0040 mg/kg in phase I and 0.041 ± 0.0039 mg/kg in phase II, respectively. The coadministration of fentanyl with tramadol induced synergism in both phases of the test with an interaction index of 0.343 and 0.163 for phase I and phase II, respectively. This finding could be explained by the more complex pharmacology of tramadol compared to fentanyl.

Examination of the interaction between peripheral lumiracoxib and opioids on the 1% formalin test in rats

It has been shown that the association of non-steroidal anti-inflammatory drugs (NSAIDs) with opioid analgesic agents can increase their antinociceptive activity, allowing the use of lower doses and thus limiting side effects. Therefore, the aim of the present study was to examine the possible pharmacological interaction between lumiracoxib and codeine or nalbuphine at the local peripheral level in the rat using the 1% formalin test and isobolographic analysis. Lumiracoxib, codeine, nalbuphine or fixed-dose ratios lumiracoxib-codeine or lumiracoxib-nalbuphine combinations were administrated locally in the formalin-injured paw and the antinociceptive effect was evaluated using the 1% formalin test. All treatments produced a dose-dependent antinociceptive effect. ED(40) values were estimated for the individual drugs and an isobologram was constructed. The derived theoretical ED(40)'s for the lumiracoxib-codeine and lumiracoxib-nalbuphine combinations were 423.4+/-31.3 microg/paw and 310.9+/-24.2 microg/paw, respectively, being significantly higher than the actually observed experimental ED(40) values, 233.2+/-30.9 microg/paw and 132.7+/-11.6 microg/paw, respectively. These results correspond to a synergistic interaction between lumiracoxib and opioids at the local peripheral level, potency being about two times higher with regard to that expected from the addition of the effects of the individual drugs. Data suggest that low doses of the lumiracoxib-opioids combination can interact synergistically at the peripheral level and therefore this drug association may represent a therapeutic advantage for the clinical treatment of inflammatory pain.

The role of cyclo-oxygenase inhibitors in attenuating opioid-induced tolerance, hyperalgesia, and dependence

There is no denying that opioids are the most important analgesic drugs which are widely used in clinical situations. Still, prolonged administration of these drugs can cause to reduce their analgesic efficacy due to the development of tolerance. These drugs can also cause induction of hyperalgesia. In addition, long-term administration of opioids through reinforcing- and rewarding pathways of limbic system can result in expression of opioid dependence with the unintended consequences of opioid abuse/misuse and finally opioid addiction. As studies show, over-activity in cyclo-oxygenase pathways and production of prostaglandins due to long-term exposures of opioid have a critical role in the development of tolerance to antinociceptive effect of opioid, hyperalgesia, and opioid dependence. The present study aims at suggesting the hypothesis that through blending a non-steroid anti-inflammatory drug with opioid actively causes reduction in unwanted effects of opioid i.e. by inhibition of opioid-induced cyclo-oxygenase overactivity whereas it is well-known that the combination therapy via reducing opioid dosage reduces the unwanted effects.

Effect of diclofenac with B vitamins on the treatment of acute pain originated by lower-limb fracture and surgery

The aim of this study was to compare the efficacy of diclofenac, for the treatment of acute pain originated by lower-limb fracture and surgery, with that of diclofenac plus B vitamins. This was a single-center, prospective, randomized, and double-blinded clinical trial. Patients with lower-limb closed fractures rated their pain on a 10 cm visual analog scale (VAS). Patients were then randomized to receive diclofenac or diclofenac plus B vitamins (thiamine, pyridoxine, and cyanocobalamin) intramuscularly twice daily. Patient evaluations of pain intensity were recorded throughout two periods: twenty-four hours presurgery and twenty-four hours postsurgical. One hundred twenty-two patients completed the study. The subjects' assessments of limb pain on the VAS showed a significant reduction from baseline values regardless of the treatment group. Diclofenac plus B vitamins combination was more effective to reduce the pain than diclofenac alone. The results showed that the addition of B vitamins to diclofenac increased its analgesic effect. The novelty of this paper consists in that diclofenac and diclofenac plus B vitamins were useful for treatment of acute pain originated by lower-limb fracture and surgery.

Systematic quantitative characterization of cellular responses induced by multiple signals

Background

Cells constantly sense many internal and environmental signals and respond through their complex signaling network, leading to particular biological outcomes. However, a systematic characterization and optimization of multi-signal responses remains a pressing challenge to traditional experimental approaches due to the arising complexity associated with the increasing number of signals and their intensities.

Results

We established and validated a data-driven mathematical approach to systematically characterize signal-response relationships. Our results demonstrate how mathematical learning algorithms can enable systematic characterization of multi-signal induced biological activities. The proposed approach enables identification of input combinations that can result in desired biological responses. In retrospect, the results show that, unlike a single drug, a properly chosen combination of drugs can lead to a significant difference in the responses of different cell types, increasing the differential targeting of certain combinations. The successful validation of identified combinations demonstrates the power of this approach. Moreover, the approach enables examining the efficacy of all lower order mixtures of the tested signals. The approach also enables identification of system-level signaling interactions between the applied signals. Many of the signaling interactions identified were consistent with the literature, and other unknown interactions emerged.

Conclusions

This approach can facilitate development of systems biology and optimal drug combination therapies for cancer and other diseases and for understanding key interactions within the cellular network upon treatment with multiple signals.

Antinociceptive and anti-exudative synergism between dexketoprofen and tramadol in a model of inflammatory pain in mice

Preclinical studies have demonstrated antinociceptive synergism between dexketoprofen (DEX) and tramadol (TRM) in acute animal models of nociception. The aim of the present study was to investigate the type of interaction between DEX and TRM in a chronic musculoskeletal pain model in mice, which fairly replicates the characteristics of chronic osteoarticular pain in humans. Inflammation was induced by a subplantar injection of complete Freund's adjuvant (CFA) in male CF1 mice. Nociceptive thresholds were evaluated using the hot plate, the nocifensive spontaneous behavior and the acetone tests, while plasma extravasation (PE) was assessed with Evan's blue. We used the following experimental groups: control (no inflammation), acute (1 day after CFA injection), and chronic inflammation (7 days after CFA). Dose-response curves for DEX and TRM, individually and combined in a 1 : 1 proportion based on their potency were obtained, and the doses that produced a 50% inhibition calculated. The isobolographic analysis revealed that in all groups of study (no inflammation, acute, and chronic inflammation), the combination of DEX : TRM was synergistic, for both the inhibition of nociception and the PE. The results suggest that the DEX : TRM (1 : 1) combination could be useful in the management of acute and chronic inflammatory musculoskeletal pains in humans; in addition, the synergistic interaction between the drugs observed both during acute and chronic inflammation suggests that less doses would be required of each drug to obtain effective analgesia.

Synergistic effect of the interaction between naproxen and citral on inflammation in rats

The combination of non-steroidal anti-inflammatory drugs with herbs having analgesic effects can increase their antinociceptive activity and limit their side effects. The aim of the present study was to examine the effects on inflammation and gastric injury in rats resulting from the interaction between naproxen and citral. Naproxen, citral, or fixed-dose naproxen-citral combinations were administered orally and their anti-inflammation (carrageenan-induced paw edema) and gastric damage were assessed in rats. The pharmacological interaction type was evaluated by the isobolographic analysis. Naproxen, citral, or combinations of naproxen and citral produced anti-inflammatory effects. The sole administration of naproxen produced significant gastric damage, but this effect was not obtained with either citral or combinations. ED(30) values were estimated for the individual drugs, and isobolograms were constructed. The derived theoretical ED(30) for the anti-inflammatory effect was 504.4 mg/kg; this was significantly higher than the observed experimental value (190.6 mg/kg). These results indicate that a synergistic interaction underlies the anti-inflammatory effect. The data suggests that the naproxen-citral combination can interact and to produce minor gastric damage and may have therapeutic advantages for the clinical treatment of inflammation.

Primary dysmenorrhea among Mexican university students: prevalence, impact and treatment

OBJECTIVE

To evaluate the prevalence, impact and treatment of primary dysmenorrhea among Mexican university students.

STUDY DESIGN

A multiple-choice questionnaire was administered to 1539 students in six university programs: medicine, nursing, nutrition, dentistry, pharmacy and psychology. Data on the presence, severity, symptoms, treatment and limitations caused by dysmenorrhea were obtained and analyzed.

RESULTS

The mean+/-SD age of the women was 20.4+/-2.0 years; the mean age of menarche was 12.3+/-1.5 years. A total of 64% of the women experienced dysmenorrhea. Dysmenorrhea was more prevalent among nutrition and psychology students than among medicine, pharmacy and dentistry students (p<0.05). Dysmenorrhea was mild in 36.1% of women, moderate in 43.8% and severe in 20.1%. Nursing students showed an intensity of pain that was significantly higher than that of medicine and dentistry students (p<0.05). Sixty-five percent of the women with dysmenorrhea reported that it limited their daily activities, and 42.1% reported school absenteeism (SA) as a result. Of those who experienced dysmenorrhea, 25.9% consulted a physician, and 61.7% practiced self-medication (SM). The most common medications used were an over-the-counter (OTC) medication with paracetamol (an analgesic), pamabrom (a diuretic), and pyrilamine (a histamine antagonist), another OTC with metamizol (a non-steroidal anti-inflammatory drug [NSAID]) plus butylhioscine (an antispasmodic drug) and naproxen (a NSAID). Of those women using prescribed medications, 18.4% reported complete remission of their symptoms, while 78.1% reported little to moderate alleviation, and 3.6% reported no effect on their menstrual distress. Similarly, of the women who practiced SM, 23.4% reported complete relief, 75.5% reported little to moderate effectiveness, and 1.0% reported no efficacy.

CONCLUSION

The prevalence of dysmenorrhea among Mexican university students is high, and the pain that these women suffer can be severe, disabling and result in short-term SA. The pain is often not completely relieved despite the use of medication. It is necessary to improve the therapeutic options for relief of pain caused by dysmenorrhea and to minimize the impact of dysmenorrhea on social, economic and school activities.

Combining paracetamol (acetaminophen) with nonsteroidal antiinflammatory drugs: a qualitative systematic review of analgesic efficacy for acute postoperative pain

BACKGROUND

There has been a trend over recent years for combining a nonsteroidal antiinflammatory drug (NSAID) with paracetamol (acetaminophen) for pain management. However, therapeutic superiority of the combination of paracetamol and an NSAID over either drug alone remains controversial. We evaluated the efficacy of the combination of paracetamol and an NSAID versus either drug alone in various acute pain models.

METHODS

A systematic literature search of Medline, Embase, Cumulative Index to Nursing and Allied Health Literature, and PubMed covering the period from January 1988 to June 2009 was performed to identify randomized controlled trials in humans that specifically compared combinations of paracetamol with various NSAIDs versus at least 1 of these constituent drugs. Identified studies were stratified into 2 groups: paracetamol/NSAID combinations versus paracetamol or NSAIDs. We analyzed pain intensity scores and supplemental analgesic requirements as primary outcome measures. In addition, each study was graded for quality using a validated scale.

RESULTS

Twenty-one human studies enrolling 1909 patients were analyzed. The NSAIDs used were ibuprofen (n = 6), diclofenac (n = 8), ketoprofen (n = 3), ketorolac (n = 1), aspirin (n = 1), tenoxicam (n = 1), and rofecoxib (n = 1). The combination of paracetamol and NSAID was more effective than paracetamol or NSAID alone in 85% and 64% of relevant studies, respectively. The pain intensity and analgesic supplementation was 35.0% +/- 10.9% and 38.8% +/- 13.1% lesser, respectively, in the positive studies for the combination versus paracetamol group, and 37.7% +/- 26.6% and 31.3% +/- 13.4% lesser, respectively, in the positive studies for the combination versus the NSAID group. No statistical difference in median quality scores was found between experimental groups.

CONCLUSION

Current evidence suggests that a combination of paracetamol and an NSAID may offer superior analgesia compared with either drug alone.

Interaction between Heliopsis longipes extract and diclofenac on the thermal hyperalgesia test

Heliopsis longipes is an herbaceous plant found in Mexico, used traditionally for its analgesic and anesthetic activities. Plant extracts in combined use with synthetic drugs may represent a therapeutic advantage for the clinical treatment of pain, allowing the use of lower doses, and limiting side-effects. Therefore, the main objective of this study was to determine the possible pharmacological interaction between Heliopsis longipes ethanolic extract (HLEE) and diclofenac in the Hargreaves model of thermal hyperalgesia in the mouse. HLEE, diclofenac or fixed-dose ratio HLEE-diclofenac combinations were administered systemically to mice and the antihyperalgesic effect was evaluated using the thermal hyperalgesia test. All treatments produced a dose-dependent antihyperalgesic effect. ED(30) values were estimated for all the treatments and an isobologram was constructed. The derived theoretical ED(30) value for the HLEE-diclofenac combination was 54.4+/-9.4 mg/kg body wt, significantly higher than the actually observed experimental ED(30) value, 8.6+/-4.0 mg/kg body wt. This result corresponds to synergistic interaction between HLEE and diclofenac in the Hargreaves model of thermal hyperalgesia. Data suggest that low doses of the HLEE-diclofenac combination can interact synergistically at the systemic level and that this association may therefore represent a therapeutic advantage for the clinical treatment of inflammatory pain.

Mechanisms of drug combinations: interaction and network perspectives

Understanding the molecular mechanisms underlying synergistic, potentiative and antagonistic effects of drug combinations could facilitate the discovery of novel efficacious combinations and multi-targeted agents. In this article, we describe an extensive investigation of the published literature on drug combinations for which the combination effect has been evaluated by rigorous analysis methods and for which relevant molecular interaction profiles of the drugs involved are available. Analysis of the 117 drug combinations identified reveals general and specific modes of action, and highlights the potential value of molecular interaction profiles in the discovery of novel multicomponent therapies.

A patient-based national survey on postoperative pain management in France reveals significant achievements and persistent challenges

We carried out a national survey on postoperative pain (POP) management in a representative sample (public/private, teaching/non-teaching, size) of 76 surgical centers in France. Based on medical records and questionnaires, we evaluated adult patients 24h after surgery, concerning information: pre and postoperative pain, evaluation, treatment and side effects. A local consultant provided information about POP management. Data were recorded for 1900 adult patients, 69.3% of whom remembered information on POP. Information was mainly delivered orally (90.3%) and rarely noted on the patient's chart (18.2%). Written evaluations of POP were frequent on the ward (93.7%) with appropriate intervals (4.1 (4.0)h), but not frequently prescribed (32.7%). Pain evaluations were based on visual analog scale (21.1%), numerical scale (41.2%), verbal scale (13.8%) or non-numerical tool (24%). Pain was rarely a criterion for recovery room discharge (19.8%). Reported POP was mild at rest (2.7 (1.3)), moderate during movement (4.9 (1.9)) and intense at its maximal level (6.4 (2.0)). Incidence of side effects was similar according to patient (26.4%) or medical chart (25.1%) including mostly nausea and vomiting (83.3%). Analgesia was frequently initiated during anesthesia (63.6%). Patient-controlled analgesia (21.4%) was used less frequently than subcutaneous morphine (35.1%) whose prescription frequently did not follow guidelines. Non-opioid analgesics used included paracetamol (90.3%), ketoprofen (48.5%) and nefopam (21.4%). Epidural (1.5%) and peripheral (4.7%) nerve blocks were under used. Evaluation (63.4%) or treatment (74.1%) protocols were not available for all patients. This national, prospective, patient-based, survey reveals both progress and persistent challenges in POP management.

Prolonged-release oxycodone enhances the effects of existing gabapentin therapy in painful diabetic neuropathy patients

BACKGROUND

Neuropathic pain remains one of the most challenging pain syndromes; under-diagnosed, poorly managed and associated with significant co-morbidity. With standard therapeutic treatments, responders rarely exceed 50% pain relief and the majority suffer from residual pain. Titration to optimum dose is often limited by dose-related adverse events.

AIMS

This randomized, double-blind, placebo-controlled study assessed the potential benefit of adding oxycodone (OxyContin tablets) to gabapentin. The primary endpoint was to evaluate the analgesic efficacy of co-administration of gabapentin and prolonged-release oxycodone, whilst also evaluating the use of escape medication, sleep quality and global assessment of pain.

METHODS

Three hundred and thirty eight patients with moderate to severe painful diabetic neuropathy despite receiving their maximum tolerated dose of gabapentin, had oral prolonged-release oxycodone or placebo tablets added to their therapy for up to 12 weeks.

RESULTS

Oxycodone-gabapentin reduced pain score by 33% from baseline to end of treatment. The overall treatment effect was greater with oxycodone-gabapentin than with placebo-gabapentin (P = 0.007). Oxycodone-gabapentin also significantly improved pain relief vs gabapentin alone (P = 0.003). Oxycodone-gabapentin co-administration was associated with less escape medication use (P = 0.03) and fewer nights of disturbed sleep (P < 0.05). Discontinuations due to lack of therapeutic effect were much lower (14% vs 54%) with oxycodone-gabapentin. The commonly seen opiate-induced adverse events were not exacerbated by the combination of oxycodone and gabapentin.

CONCLUSIONS

This study provides the first evidence that co-administration of prolonged-release oxycodone and existing gabapentin therapy has a clinically meaningful effect in painful diabetic neuropathy.

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.

The Role of the Anesthesiologist in Fast-Track Surgery: From Multimodal Analgesia to Perioperative Medical Care

BACKGROUND

Improving perioperative efficiency and throughput has become increasingly important in the modern practice of anesthesiology. Fast-track surgery represents a multidisciplinary approach to improving perioperative efficiency by facilitating recovery after both minor (i.e., outpatient) and major (inpatient) surgery procedures. In this article we focus on the expanding role of the anesthesiologist in fast-track surgery.

METHODS

A multidisciplinary group of clinical investigators met at McGill University in the Fall of 2005 to discuss current anesthetic and surgical practices directed at improving the postoperative recovery process. A subgroup of the attendees at this conference was assigned the task of reviewing the peer-reviewed literature on this topic as it related to the role of the anesthesiologist as a perioperative physician.

RESULTS

Anesthesiologists as perioperative physicians play a key role in fast-track surgery through their choice of preoperative medication, anesthetics and techniques, use of prophylactic drugs to minimize side effects (e.g., pain, nausea and vomiting, dizziness), as well as the administration of adjunctive drugs to maintain major organ system function during and after surgery.

CONCLUSION

The decisions of the anesthesiologist as a key perioperative physician are of critical importance to the surgical care team in developing a successful fast-track surgery program.

An isobolographic analysis of diamorphine and levobupivacaine for epidural analgesia in early labour

BACKGROUND

Few data describe the pharmacological interactions between local anaesthetics and opioids. The aim of this study was to measure the median effective concentration (MEC) of diamorphine and levobupivacaine when given separately and as mixtures for epidural analgesia, and determine whether the combination is additive or synergistic.

METHODS

One hundred and twenty patients were enrolled in this prospective randomized, two-phase, double-blind study. In the first phase, 60 women were randomized to receive a fixed 20 ml volume of either levobupivacaine or diamorphine epidurally . Dosing was determined using up-down sequential allocation with testing intervals, respectively, of 0.01%w/v and 12.5 microg ml(-1). After estimations of the MEC of levobupivacaine and diamorphine, a further 60 patients were randomized in the second phase to one of the three mixtures: (a) diamorphine 70 microg ml(-1) (fixed) and levobupivacaine (testing interval 0.004%w/v, starting at 0.044%w/v); (b) levobupivacaine 0.044%w/v (fixed) and diamorphine (testing interval 7 microg ml(-1), starting at 70 microg ml(-1)); and (c) bivariate diamorphine and levobupivacaine (testing intervals of 7 microg ml(-1) and 0.004%w/v starting at 70 microg ml(-1) and 0.044% w/v respectively).

RESULTS

The MEC estimates from the first phase were 143.8 microg ml(-1) (95% CI 122.2-165.3) for diamorphine and 0.083%w/v (95% CI 0.071-0.095) for levobupivacaine. In the second phase, the MEC and interaction index (gamma) of the three combinations were: diamorphine 65.5 microg ml(-1) (56.8-74.2), gamma = 0.99; levobupivacaine 0.041%w/v (0.037-0.049), gamma = 0.98; and for the fixed combination diamorphine 69.5 microg ml(-1) (60.5-78.5) and levobupivacaine 0.044%w/v (0.039-0.049), gamma = 1.02.

CONCLUSION

The combination of diamorphine and levobupivacaine is additive and not synergistic when used for epidural analgesia in the first stage of labour.

A new model for drug interactions and optimal drug dosing

Drugs are routinely combined in anesthesia and pain management to obtain an enhancement of the desired effects. However, a parallel enhancement of the undesired effects might take place as well, resulting in a limited therapeutic usefulness. Therefore, when addressing the question of optimal drug combinations, side effects must be taken into account. We propose a new method to study drug interactions considering also their side effects and to identify optimal drug dosing. The model is consistent with clinical knowledge and can explain previously published experimental results, improving our understanding of the characteristics of drug combinations used in clinical practice.

Dipyrone potentiates morphine-induced antinociception in dipyrone-treated and morphine-tolerant rats

Coadministration of morphine and dipyrone produces acute and chronic antinociceptive potentiation in drug-naive rats. In this work, the effectiveness of the combination was determined in rats pretreated with morphine or dipyrone. Nine groups of male rats received (i.v.) 3.1 mg/kg morphine, 600 mg/kg dipyrone, or the morphine-dipyrone combination twice a day for five administrations (three groups per treatment). From the 6th to the 10th administration, one group out of each treatment continued without change, while the other two were switched to one of the other two possible treatments. In morphine-tolerant rats, morphine plus dipyrone produced a transient antinociceptive potentiation. In dipyrone-treated animals, this combination produced a long-lasting potentiation. In animals only treated with the combination, antinociception was clear since the beginning, although it decreased after the 6th injection. No cross-tolerance was seen between morphine and dipyrone. These data suggest that dipyrone potentiates morphine-induced antinociception in dipyrone-treated as well as in morphine-tolerant rats.

Section 4

Physicians may choose from a variety of pharmacologic and nonpharmacologic options to treat patients with painful rheumatic diseases. Osteoarthritis (OA) is the most common type of arthritis requiring pain management. New disease-modifying antirheumatic drugs and biologic response modifiers can improve disease states in patients with rheumatoid arthritis (RA). After the inflammatory component of RA is minimized with such agents, treatment goals shift to those similar to secondary OA and other degenerative joint diseases. Relief of pain and improvement in functional status are essential components of effective therapy. A pure analgesic such as acetaminophen and nonsteroidal antiinflammatory drugs, including the cyclooxygenase-2-selective inhibitors for those at risk for gastrointestinal side effects, may be used at the lowest effective doses. Combination therapy for acetaminophen and an opioid may maximize pain relief and provide greater speed and duration of action than the separate components. Use of the atypical opioid tramadol with acetaminophen often results in an improved side-effect profile compared with stronger opioids, with similar levels of pain relief. Adjunctive therapy with agents such as topical analgesics, intraarticular hyaluron, tricyclic antidepressants, anticonvulsants, muscle relaxants, and anxiolytics may also be helpful. Nonpharmacologic therapies such as exercise, physical therapy, and psychologic counseling may also diminish pain and improve outcome in patients with rheumatic diseases. One may also consider yoga, acupuncture, biofeedback, massage, relaxation techniques, and other alternative therapies.