Semi-mechanistic modeling of the interaction between the central and peripheral effects in the antinociceptive response to lumiracoxib in rats

The model-based approach was undertaken to characterize the interaction between the peripheral and central antinociceptive effects exerted by lumiracoxib. The effects of intraplantar and intrathecal administrations and of fixed ratio combinations of lumiracoxib simultaneously administered by these two routes were evaluated using the formalin test in rats. Pain-related behavior data, quantified as the number of flinches of the injected paw, were analyzed using a population approach with NONMEM 7. The pain response during the first phase of the formalin test, which was insensitive to lumiracoxib, was modeled using a monoexponential decay. The second phase, which was sensitive to lumiracoxib, was described incorporating synthesis and degradation processes of pain mediators that were recruited locally after tissue injury. Upregulation at the local level and in the central nervous system (CNS) was set to be proportional to the predicted levels of pain mediators in the local (injured) compartment. Results suggest a greater role of upregulated COX-2(Local) in generating the pain response compared to COX-2(CNS). Drug effects were described as inhibition of upregulated COX-2. The model adequately described the time course of nociception after formalin injection in the absence or presence of lumiracoxib administered locally and/or spinally. Data suggest that the overall response is the additive outcome of drug effects at the peripheral and central compartments, with predominance of peripheral mechanisms. Application of modeling opens new perspectives for understanding the overall mechanism of action of analgesic drugs.

Evidence for the Participation of ATP-sensitive Potassium Channels in the Antinociceptive Effect of Curcumin

Background

It has been reported that curcumin, the main active compound of Curcuma longa, also known as turmeric, exhibits antinociceptive properties. The aim of this study was to examine the participation of ATP-sensitive potassium channels (K_ATP channels) and, in particular, that of the L-arginine-nitric oxide-cyclic GMP-K_ATP channel pathway, in the antinociceptive effect of curcumin.

Methods

Pain was induced by the intraplantar injection of 1% formalin in the right hind paw of Wistar rats. Formalin-induced flinching behavior was interpreted as an expression of nociception. The antinociceptive effect of oral curcumin was explored in the presence and absence of local pretreatment with L-NAME, an inhibitor of nitric oxide synthase, ODQ, an inhibitor of soluble guanylyl cyclase, and glibenclamide, a blocker of K_ATP channels.

Results

Oral curcumin produced a dose-dependent antinociceptive effect in the 1% formalin test. Curcumin-induced antinociception was not altered by local L-NAME or ODQ, but was significantly impaired by glibenclamide.

Conclusions

Our results confirm that curcumin is an effective antinociceptive agent. Curcumin-induced antinociception appears to involve the participation of K_ATP channels at the peripheral level, as local injection of glibenclamide prevented its effect. Activation of K_ATP channels, however, does not occur by activation of the L-arginine-nitric oxide-cGMP-K_ATP channel pathway.

Role of ATP-sensitive K+ channels in the antinociception induced by non-steroidal anti-inflammatory drugs in streptozotocin-diabetic and non-diabetic rats

There is evidence that systemic sulfonylureas block diclofenac-induced antinociception in normal rat, suggesting that diclofenac activates ATP-sensitive K(+) channels. However, there is no evidence for the systemic interaction between different non-steroidal anti-inflammatory drugs (NSAIDs) and sulfonylureas in streptozotocin (STZ)-diabetic rats. Therefore, this work was undertaken to determine whether two sulfonylureas, glibenclamide and glipizide, have any effect on the systemic antinociception that is induced by diclofenac (30 mg/kg), lumiracoxib (56 mg/kg), meloxicam (30 mg/kg), metamizol (56 mg/kg) and indomethacin (30 mg/kg) using the non-diabetic and STZ-diabetic rat formalin test. Systemic injections of NSAIDs produced dose-dependent antinociception during the second phase of the test in both non-diabetic and STZ-diabetic rats. Systemic pretreatment with glibenclamide (10 mg/kg) and glipizide (10 mg/kg) blocked diclofenac-induced systemic antinociception in the second phase of the test (P<0.05) in both non-diabetic and STZ-diabetic rats. In contrast, pretreatment with glibenclamide or glipizide did not block lumiracoxib-, meloxicam-, metamizol-, and indomethacin-induced systemic antinociception (P>0.05) in both groups. Results showed that systemic NSAIDs are able to produce antinociception in STZ-diabetic rats. Likewise, data suggest that diclofenac, but not other NSAIDs, activated K(+) channels to induce its systemic antinociceptive effect in the non-diabetic and STZ-diabetic rat formalin test.

Procedural pain and anxiety in paediatric patients in a Mexican emergency department

AIM

This article is a report of a study carried out to investigate the procedures that are likely to induce pain and anxiety in children in a Mexican emergency department.

BACKGROUND

In emergency rooms, children often experience unpredictable diagnostic and therapeutic procedural-related pain that can be associated with considerable anxiety.

DESIGN

A prospective, descriptive and cross sectional study was conducted to investigate the prevalence of procedures or situations that probably induced anxiety and/or pain in children in an emergency room.

METHODS

Procedural pain and anxiety were evaluated in children and adolescents (8-16 years) who were admitted to the emergency department of a paediatric hospital between February-September 2010. Children rated their pain and anxiety using a 100-mm visual analogue scale.

RESULTS

A total of 252 children with a mean age of 10·1 years were evaluated. Four-hundred fifty-nine procedures were completed, with an average of 1·82 events/child. Of these procedures, 369 (80·4%) were rated painful and 357 (77·8%) were rated stressful. The most frequently reported procedural pain or stressful episodes were peripheral catheterization, clinical examination and vascular puncture. Overall, 32·5% of the painful events were rated severe, 32·0% were rated moderate and 35·5% were rated slight. However, 30% of the stressful events were rated severe, 38·9% were rated moderate and 31·1% were rated slight. Peripheral catheterization was rated severe in 58 children (33·9%), moderate in 55 children (32·2%) and slight in 58 (33·9%) children.

CONCLUSION

This study provides data on common emergency department procedures that cause pain and anxiety in children and young adolescents. Healthcare providers must consider the best psychological and pharmacological interventions to reduce procedural anxiety and pain.

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.

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.

Metformin and phenformin block the peripheral antinociception induced by diclofenac and indomethacin on the formalin test

AIMS

Recent evidence has shown that systemic administration of sulfonylureas and biguanides block the diclofenac-induced antinociception, but not the effect produced by indomethacin. However, there are no reports about the peripheral interaction between analgesics and the biguanides metformin and phenformin. Therefore, this work was undertaken to determine whether glibenclamide and glipizide and the biguanides metformin and phenformin have any effect on the peripheral antinociception induced by diclofenac and indomethacin.

MAIN METHODS

Diclofenac and indomethacin were administered locally in the formalin-injured rat paw, and the antinociceptive effect was evaluated using the 1% formalin test. To determine whether peripheral antinociception induced by diclofenac or indomethacin was mediated by either the ATP-sensitive K(+) channels or biguanides-induced mechanisms, the effect of pretreatment with the appropriates vehicles or glibenclamide, glipizide, metformin and phenformin on the antinociceptive effect induced by local peripheral diclofenac and indomethacin was assessed.

KEY FINDINGS

Local peripheral injections of diclofenac (50-200 μg/paw) and indomethacin (200-800 μg/paw) produced a dose-dependent antinociception during the second phase of the test. Local pretreatment with glibenclamide, glipizide, metformin and phenformin blocked the diclofenac-induced antinociception. On the other hand, the pretreatment with glibenclamide and glipizide did not prevent the local antinociception produced by indomethacin. Nonetheless, metformin and phenformin reversed the local antinociception induced by indomethacin.

SIGNIFICANCE

Data suggest that diclofenac could activate the K(+) channels and biguanides-dependent mechanisms to produce its peripheral antinociceptive effects in the formalin test. Likewise, a biguanides-dependent mechanism could be activated by indomethacin consecutively to generate its peripheral antinociceptive effect.

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.

Antinociceptive, genotoxic and histopathological study of Heliopsis longipes S.F. Blake in mice

ETHNOPHARMACOLOGICAL RELEVANCE

H. longipes S.F. Blake (Asteraceae) is a Mexican plant, whose roots are traditionally used as a condiment, as a mouth anesthetic, and as an antiparasitic. Affinin is the alkamide present in higher amounts in the roots of H. longipes.

AIM OF THE STUDY

To date, there are no published studies regarding the relation between the analgesic properties, in vivo cytotoxicity, and DNA-damaging potential of H. longipes ethanol extract (HLEE).

MATERIALS AND METHODS

The HLEE was chromatographically fingerprinted to validate its affinin contents. Biological evaluation was conducted in sets of 6-8 CD1(+) mice. Antinociceptive effect was evaluated using the writhing and hot-plate tests, and mutagenic and cytotoxic effects were evaluated with micronucleous test in CD1(+) mice. For histopathological studies, biological samples from liver, heart, kidneys, spleen, lung, and brain were collected and stained.

RESULTS

Oral administration of HLEE (3-100 mg/kg) produced a dose-dependent antinociceptive effect in both assays. In micronucleus assay, the variability in the number of micronucleated polychromatic erythrocytes (MNPE) induced, and PE/NE index, the ratio of polychromatic erythrocytes with respect to the number of normochromatic erythrocytes induced by HLEE in the evaluated schedule, were small and nonsignificant. After histopathological results, HLEE showed polioencephalomalacia with 1000 mg/kg dose.

CONCLUSIONS

This work provides evidence that HLEE exerts analgesic effects, with no genotoxic effects in vivo. These findings would be an important contribution to explain the use of H. longipes root as an effective analgesic in traditional medicine, and to establish for the first time the absence of genotoxic and cytotoxic effects of the root in bioactive doses in vivo.

No differences in the Sry gene between males and XY females in Akodon (Rodentia, Cricetidae)

Several species of the South American genus Akodon present fully fertile XY females besides XX ones. To analyze the possibility of a Sry mutation as the cause of sex reversal in A. azarae and A. boliviensis, we determined the sequence of the Sry gene in 2 males and 3 XY females from each of these species. The Sry gene sequence was also studied in A. dolores, a species that does not have XY females. In inter-specific comparisons, the percentage identities with respect to the region analyzed varied between 96.8% and 97.9%. An ORF of 543 nucleotides was identified, and the predicted Sry proteins comprised 180 amino acids, with an HMG domain of 83 amino acids. Our results indicate that female sex reversal in A. azarae and A. boliviensis cannot be explained by sequence differences in the Sry region analyzed here, which includes the complete ORF and, together with previous results concerning the inheritance of the XY condition, show that Sry mutation is not the basis of sex reversal.

Pharmacokinetic of diclofenac in the presence and absence of glibenclamide in the rat

PURPOSE

There is evidence that the sulfonylurea antidiabetic agent glibenclamide reduces the analgesic action of non-steroidal anti-inflammatory drugs (NSAIDs), opioids and neuromodulators in animal models. Therefore, in view of the vast clinical uses and interactions of NSAIDs with commonly used therapeutic agents, the interaction of the NSAID diclofenac and glibenclamide was investigated about pharmacokinetic profile and antinociceptive effect in rats.

METHODS

Antinociception was assessed using the formalin test. Fifty microliters of diluted formalin was injected s.c. into the dorsal surface of the right hind paw. Nociceptive behavior was quantified as the number of flinches of the injected paw during 60 min after injection. Rats were treated with oral administration of vehicle or increasing doses of diclofenac (3-18 mg/kg) before formalin injection. To determine the pharmacodynamic interaction between diclofenac and glibenclamide, the effect of oral administration of glibenclamide (1-30 mg/kg) on the antinociceptive effect induced by diclofenac (18 mg/kg, p.o.) was assessed. To evaluate the pharmacokinetic interaction between diclofenac and glibenclamide, the effect of glibenclamide (10 mg/kg, p.o.) on the pharmacokinetic of diclofenac (18 mg/kg, p.o.) was studied in the rat. Blood samples were taken over 8 h and analyzed using a validated high-performance liquid chromatography method to generate the pharmacokinetic profile of diclofenac. Pharmacokinetic parameters were estimated using noncompartmental analysis.

RESULTS

Systemic administration of diclofenac produced a dose-dependent antinociceptive effect in the formalin test. Systemic treatment with glibenclamide prevented diclofenac-induced antinociception. In pharmacokinetic interaction study, no significant (P>0.05) change in diclofenac concentration-time profiles in the presence of glibenclamide was detected.

CONCLUSION

The experimental findings suggest that systemic glibenclamide is able to block the diclofenac-induced antinociception in the rat formalin test. Besides, this antagonism was not produced by diminution in the bioavailability of diclofenac. Likewise, the validated assay had sufficient accuracy and precision for pharmacokinetic determination of diclofenac in the rat.

Pharmacovigilance of psychoactive medications in a Mexican psychiatric hospital

Pharmacovigilance is the permanent collection and assessment of the safety data of drugs in the interest of precise knowledge of the safety profile. We monitored notifications of suspected adverse reactions (AR) produced by psychoactive medications (ARPM) in a Psychiatry Hospital, during a 4-month period. Yellow cards for adverse reaction reporting were distributed to the medical personal at the Hospital Psiquiátrico Villa Ocaranza, Pachuca Hidalgo, Mexico. For each notification, the ARPM was analyzed in order to verify causality. One hundred twelve hospitalized patients entered the study (44 male and 68 female). The mean +/- SD age of the patients was 46 +/- 4.5 years. The major diagnoses found were: schizophrenia (35.7%), severe mental retardation (17 %), moderate mental retardation (MMR)/epilepsy (12.5%), MMR (8.03%), and others (26.7%). During the study there were 721 therapeutic regimens prescribed to patients on psychiatric service. Patients were receiving an average of 5.3 +/- 1.1 (range 4 to 8) psychiatric medications. The psychiatrists reported only 5 ARPMs in five patients (prevalence: 4.46%). Among the drugs involved were neuroleptics (47.8%), antiepileptic (39.1%), and others (13.04%). The organs and systems affected by the ARs were the central nervous system, skin, endocrinological and gastrointestinal. A causal association between the medication and the AR were classified as probable in three cases, as possible in one case, as doubtful in one case and as definite in no case.

Effectiveness of diclofenac, ketorolac and etoricoxib in the treatment of acute pain from ankle fracture

Tissue degeneration, infection, inflammation, cancer, trauma, surgery and limb fractures all produce pain. Each of these physiological abnormalities requires a therapeutic approach different from the last. In acute pain, caused by fracture, several classes of analgesics have been utilized. These basic remedies for analgesia, however, are still confined to a small number of medications, including nonsteroidal anti-inflammatory drugs (NSAIDs), local anesthetics and opioids. In addition, most of these drugs have side effects, limiting their use in clinical practice. The purpose of this study was to compare the efficacy of three NSAIDs to relief acute pain caused by ankle fracture. Sixty subjects with ankle fracture were randomized to receive ketorolac, diclofenac, or etoricoxib, every 12 hours in a prospective, double-blind study. Forty-nine patients completed the study. The subjects' assessments of ankle pain on the visual analog scale and a Likert scale showed a significant reduction from baseline over 24 hr, regardless the treatment group. All treatments showed a similar profile in pain reduction. Etoricoxib, diclofenac and ketorolac twice daily are a rapid and effective treatment for acute pain. All the regimens were well tolerated in this study.