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Background: Combining antinociceptive drugs with different mechanisms of action can reduce the doses and the adverse effects, with a possible increase in the antinociceptive effect. This work evaluated the antinociceptive effect of the combination of an ethanol extract of Justicia spicigera (JSE) with naproxen (NPX) or tramadol (TML) using the formalin test in rats. Methods: Rats received JSE (30–200 mg/kg p.o.), NPX (50–300 mg/kg p.o.), or TML (5–50 mg/kg p.o.) 60 min before paw administration with formalin (5%). Different proportions of the combination between NPX and JSE, as well as TML and JSE, were used in the formalin test to obtain the dose–response curve of each drug and the experimental effective dose 50 (ED50). The levels of IL-1β and COX2 were assessed using a Western blot analysis as a possible mechanism of action for the combination of JSE and analgesics. A pharmacokinetic study was conducted to evaluate the effect of JSE on the pharmacokinetic parameters of NPX. Results: The ED50 values for the proportions NPX:JSE were 107.09 mg/kg (1:1), 102.44 mg/kg (3:1), and 73.82 mg/kg (1:3). The ED50 values for the proportions TML:JSE were 66 mg/kg (1:1), 29.5 mg/kg (1:3), and 78 mg/kg (3:1). The combination NPX:JSE (1:3) showed the best synergistic interaction index (0.501). The pharmacokinetic study revealed that there were no significant changes in the pharmacokinetic parameters of NPX administered individually and the combination NPX:JSE. Conclusions: In this preclinical study, the combination NPX:JSE showed antinociceptive effects by decreasing the levels of COX2 and IL-1β without affecting NPX's pharmacokinetics. [ABSTRACT FROM AUTHOR]

Background: Diverse studies suggest that non-steroidal anti-inflammatory drugs (NSAIDs) induce antinociception through the inhibition of cyclooxygenases. Objectives: This study evaluated the effect of NSAIDs in inducing antinociception either alone or in combination in mice formalin orofacial pain. Methods: Male mice were injected intraperitoneally with dexibuprofen, dexketoprofen, diclofenac meloxicam, metamizole and piroxicam. Then from a dose-response curve the ED50 (dose that produce 50% of maximum effect) was obtained from each drug. Results: The administration of NSAIDs produced a dose-dependent antinociception in both phases of the assay with different potency. Then, combinations of the cited NSAIDs were tested and analyzed by isobolographic analysis. The results demonstrate that the nocifensive response induced when dexketoprofen (DEX), the dextrorotatory enantiomer of the S (+) configuration of ketoprofen, was combined with piroxicam, diclofenac, dexibuprofen, metamizole, and meloxicam, was synergistic, either in Phase I or Phase II of the formalin orofacial mice assay. Conclusion: The data demonstrated that the NSAIDs administered alone or in combination produce antinociception. These effects need to be explained by other mechanisms of action of NSAIDs other than the simple inhibition of COXs. The findings may be relevant for the relief of acute or chronic pain such as migraine, post‐herpetic neuralgia and tooth pain.

Abstract Background: Phoneutria nigriventer venom contains Phα1β. This toxin and its recombinant form have a remarkable analgesic potential that is associated with blockage of voltage-gated calcium channels and TRPA1 receptors. Although morphine is a mainstay drug to treat moderate and severe pain related to cancer, it has serious and dose-limiting side effects. Combining recombinant Phα1β and morphine to treat pain is an interesting approach that has been gaining attention. Therefore, a quantitative and reliable method to establish the strength of the antinociceptive interaction between these two substances is necessary. The present study was designed to investigate the nature of the functional antinociceptive (analgesic) interaction between Phα1β recombinant toxin and morphine in a model of cancer pain. Methods: Melanoma was produced by intraplantar inoculation of B16-F10 cells into the right paw of C57BL/6J mice. Von Frey filaments measured the paw-withdrawal threshold after intrathecal administration of morphine, recombinant Phα1β, and their combination. Thermal hyperalgesia was assessed using Hargreaves apparatus. The degree of interaction was evaluated using isobolographic analysis. Spontaneous and forced motor performance was assessed with the open-field and rotarod tests, respectively. Results: Co-administration of recombinant Phα1β and morphine synergistically reverses the melanoma-induced mechanical hyperalgesia. The potency of the mixture, measured as the effective dose to reach 50% of maximum possible effect (MPE) in ameliorating mechanical hyperalgesia, was about twice fold higher than expected if the interaction between morphine and recombinant Phα1β was merely additive. Treatment with the combination at doses necessary to reach 50% of MPE caused no spontaneous nor forced motor alterations. Conclusion: The combinatorial use of recombinant Phα1β and morphine allows significant and effective dose reduction of both agents, which has translational potential for opioid-sparing approaches in pain management related to cancer.

Aims: To evaluate the nature of the antinociceptive interaction of systemic administration of a combination of the anticonvulsant gabapentin with the antidepressant nortriptyline, by isobolographic analysis in the formalin orofacial pain test of mice. Methods: The study was carried out in 168 male CF-1 mice weighing 30 g, and the protocol was to test each drug (at dosages of 1, 3, 10, 30, and 100 mg/kg of gabapentin and 0.1, 1, 3, 10, and 30 mg/kg of nortriptyline; ip) alone and in combination. The isobolographic assay has two phases: phase 1 corresponds to the 5-minute period starting immediately after the formalin injection and reflects a tonic acute pain due to peripheral nociceptor sensitization; phase 2 is recorded as the 10-minute period starting 20 minutes after the formalin injection and reflects an inflammatory pain state. Results were analyzed by Student t test for independent means. Results: Gabapentin was 1.61 times more potent in phase 2 than in phase 1, and nortriptyline 1.37 times more potent in phase 2 than in phase 1. The combination of both drugs was synergic, with an index of interaction of 0.134 and 0.148 for phase 1 and phase 2, respectively. Differences in the pharmacological profiles of gabapentin and nortriptyline could underlie the synergism of the two drugs. Conclusion: The findings of this study are important, because they are concordant with some clinical studies and also raise the possibility of potential clinical advantages of combining gabapentin and nortriptyline in pain management, since the low doses of the components may potentially have a lower incidence of adverse reactions. [ABSTRACT FROM AUTHOR]

Background: Evidence of Plasmodium resistance to some of the current anti-malarial agents makes it imperative to search for newer and effective drugs to combat malaria. Therefore, this study evaluated whether the co-administrations of xylopic acid-amodiaquine and xylopic acid-artesunate combinations will produce a synergistic anti-malarial effect. Methods: Antiplasmodial effect of xylopic acid (XA: 3, 10, 30, 100, 150 mg kg−1), artesunate (ART: 1, 2, 4, 8, 16 mg kg−1), and amodiaquine (AQ: 1.25, 2.5, 5, 10, 20 mg kg−1) were evaluated in Plasmodium berghei (strain ANKA)-infected mice to determine respective ED50s. Artemether/lumefantrine was used as the positive control. XA/ART and XA/AQ were subsequently administered in a fixed-dose combination of their ED50s (1:1) and the combination fractions of their ED50s (1/2, 1/4, 1/8, 1/16, and 1/32) to determine the experimental ED50s (Zexp). An isobologram was constructed to determine the nature of the interaction between XA/ART, and XA/AQ combinations by comparing Zexp with the theoretical ED50 (Zadd). Bodyweight and 30-day survival post-treatment were additionally recorded. Results: ED50s for XA, ART, and AQ were 9.0 ± 3.2, 1.61 ± 0.6, and 3.1 ± 0.8 mg kg−1, respectively. The Zadd, Zexp, and interaction index for XA/ART co-administration was 5.3 ± 2.61, 1.98 ± 0.25, and 0.37, respectively while that of XA/AQ were 6.05 ± 2.0, 1.69 ± 0.42, and 0.28, respectively. The Zexp for both combination therapies lay significantly (p < 0.001) below the additive isoboles showing XA acts synergistically with both ART and AQ in clearing the parasites. High doses of XA/ART combination significantly (p < 0.05) increased the survival days of infected mice with a mean hazard ratio of 0.40 while all the XA/AQ combination doses showed a significant (p < 0.05) increase in the survival days of infected mice with a mean hazard ratio of 0.27 similar to AL. Both XA/ART and XA/AQ combined treatments significantly (p < 0.05) reduced weight loss. Conclusion: Xylopic acid co-administration with either artesunate or amodiaquine produces a synergistic anti-plasmodial effect in mice infected with P. berghei. [ABSTRACT FROM AUTHOR]

Although nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the main types of drugs used to treat pain, they have several adverse effects, and such effects can be reduced by combining two analgesic drugs. The aim of this study was to evaluate the nociceptive activity of methyleugenol combined with either diclofenac or ketorolac, and determine certain parameters of pharmacokinetics. For the isobolographic analysis, the experimental effective dose 30 (ED30) was calculated for the drugs applied individually. With these effective doses, the peak plasma concentration (Cmax) was found and the other parameters of pharmacokinetics were established. Methyleugenol plus diclofenac and methyleugenol plus ketorolac decreased licking behavior in a dose-dependent manner in phase II, with an efficacy of 32.9 ± 9.3 and 39.8 ± 9.6%, respectively. According to the isobolographic analysis, the experimental and theoretical ED30 values were similar for methyleugenol plus diclofenac, suggesting an additive effect, but significantly different for methyleugenol plus ketorolac (3.6 ± 0.5 vs. 7.7 ± 0.6 mg/kg, respectively), indicating a probable synergistic interaction. Regarding pharmacokinetics, the only parameter showing a significant difference was Cmax for the methyleugenol plus diclofenac combination. Even with this difference, the combinations studied may be advantageous for treating inflammatory pain, especially for the combination methyleugenol plus ketorolac.

Receptor ligands in mixtures may produce effects that are greater than the effect predicted from their individual dose-response curves. The historical basis for predicting the mixture effect is based on Loewe’s concept and its mathematical formulation. This concept considers compounds with constant relative potencies (parallel dose-response curves) and leads to linear additive isoboles. These lines serve as references for distinguishing additive from nonadditive interactions according to the positions of the experimental data on or outside of the lines. In this paper, we applied a highly relevant two-state model for a description of the receptor-ligand interaction in the construction of the isobologram. In our model we consider partial agonists that have dose-response curve slopes differing from one. With this theoretical basis, we demonstrated that a combination of compounds with different efficacies leads to curved isoboles. This model should overwrite Tallarida’s flawed assumption about isobolographic analysis of partial agonists and enhance our understanding of how the partial agonists contribute to the overall mixture effect. [ABSTRACT FROM AUTHOR]

ABSTRACT [ABSTRACT FROM AUTHOR]

Aims Extensive evidence supports a role for voltage-gated calcium channels (VGCC) and TRPV1 receptors in pain transmission and modulation. We investigated the profile of analgesic interaction between Phα1β toxin (a VGCC blocker) and SB366791 (selective TRPV1 antagonist) in a model of acute pain induced by capsaicin. Changes in body temperature induced by combination regimens were also evaluated. Main methods Isobolographic approach with a fixed dose-ratio of combined drugs was used to determine whether antinociceptive interaction of Phα1β and SB366791 are subadditive, additive or synergic. Body temperature was obtained by thermal infrared imaging. Key findings Phα1β and SB366791 interact in a synergistic manner to cause antinociception. We found an interaction index (α) of 0.07 for Phα1β and SB366791 when these drugs were injected together intraplantarly, which indicates that in vivo interaction between these drugs is greater than additive interaction. Synergism also occurred when intraplantar SB366791 was administered simultaneously with intrathecal Phα1β (interaction index α = 0.06) suggesting a 15 fold rise in potency on the analgesic effect of these drugs when they are added together. It was observed no significant alterations in body temperature of animals treated with this combination regimen. Significance Our data reveal that Phα1β toxin potentiates in 15 fold the antinociceptive action of the TRPV1 blocker SB366791. Therefore, lower doses of these drugs are required to achieve antinociceptive effects when these agents are given in combination. [ABSTRACT FROM AUTHOR]

Combined therapy of ovarian cancer has a long history. It has been applied for many years. The first drug which was commonly combined with other chemotherapeutics was cisplatin. It turned out to be effective given together with alkylating agents as well as with taxanes. Another drug which is often the basis of first-line therapy is doxorubicin. The use of traditional chemotherapy is often limited due to side effects. This is why new drugs, targeted specifically at cancer cells (e.g. monoclonal antibodies or epidermal growth factor receptor inhibitors), offer a welcome addition when used in combination with conventional anticancer agents. Drugs applied in combination should be synergistic or at least additive. To evaluate the type of interaction between drugs in a plausible sequence, isobolographic analysis is used. This method allows one to assess whether the two agents could make an efficient combination, which might improve the therapy of ovarian cancer. [ABSTRACT FROM AUTHOR]

Objectives Combinations of different classes of antidepressants (including herbal adjuvants) have been used as an alternative means of achieving better results in the treatment of depressed patients. However, studies characterizing the interactions between herbal adjuvants and antidepressants are lacking. This study is the first to investigate the interaction between diene valepotriates ( VAL) from V aleriana glechomifolia, a species with antidepressant-like effects, and imipramine ( IMI), desipramine ( DESI) and bupropion ( BUP). The interactions were assessed via isobolographic analyses, which represent a tool for evaluating interactions between drugs. Methods The interaction between VAL and each antidepressant was evaluated in mice given concurrent oral administration of each drug with fixed ED50 ratios and subjected to a forced swimming test ( FST). Spontaneous locomotion was measured in the open field test. Key findings The drug combinations produced a dose-dependent anti-immobility effect in the FST without altering mouse locomotor activity. Isobolographic analysis revealed that VAL resulted in synergistic interactions in combination with each of the antidepressants tested. Conclusion The synergistic interactions between VAL and IMI, DESI and BUP highlight the potential for VAL to serve as adjuvants to antidepressant drugs and suggest that VAL does not directly target the same sites on neuronal transporters as the antidepressants. [ABSTRACT FROM AUTHOR]

Background Opioids have been used for the management of pain and coadministration of two opioids may induce synergism. In a model of tonic pain, the acetic acid writhing test and in a phasic model, the hot plate, the antinociceptive interaction between fentanyl, methadone, morphine, and tramadol was evaluated. Results The potency of opioids in the writhing test compared to the hot plate assay was from 2.5 (fentanyl) to 15.5 (morphine) times, respectively. The ED50 was used in a fixed ratio for each of the six pairs of opioid combinations, which, resulted in a synergistic antinociception except for methadone/tramadol and fentanyl/tramadol which were additive, in the hot plate. The opioid antagonists naltrexone, naltrindole and nor-binaltorphimine, suggests that the synergism of morphine combinations are due to the activation of MOR subtypes with partially contribution of DOR and KOR, however fentanyl and methadone combinations are partially due to the activation of MOR and DOR subtypes and KOR lack of participation. The antinociceptive effects of tramadol combinations, are partially due to the activation of MOR, DOR and KOR opioid subtypes. Conclusion These results suggets that effectiveness and magnitude of the interactions between opioids are dependent on pain stimulus intensity. [ABSTRACT FROM AUTHOR]

Abstract: The synergistic antioxidant effects of ethanolic extracts of Centella asiatica (CE), and α-tocopherol have been studied. The types of interactions exhibited by CE and α-tocopherol combined at different ratios were measured using three assays: 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical-scavenging capacity, the β-carotene bleaching system and liposome peroxidation assays. Fixed-fraction isobolographic analysis was used to detect any inducement of the antioxidant activity compared with the individual activities of CE and α-tocopherol. Of all synergistic combinations of CE and α-tocopherol, only fraction 2/3 showed the synergistic combination that fits well in three different assays and can be explained by the regeneration of α-tocopherol by CE despite the interaction effect of β-carotene present in the analytical assay. This phenomenon involved complex interactions between CE and α-tocopherol to exhibit different degrees of interactions that eventually increased antioxidant activity. [Copyright &y& Elsevier]

Abstract: In the treatment of acute and chronic pain the most frequently used drugs are nonsteroidal anti-inflammatory drugs (NSAIDs), e.g., paracetamol; opioids, e.g., tramadol, and a group of drugs called coanalgesics or adjuvants (e.g., antidepressants, anticonvulsants). The aim of this work was to determine the nature of the interaction induced by intraperitoneal or intrathecal coadministration of paracetamol and tramadol. The type of interaction was evaluated by means of isobolographic analysis, using the acetic acid writhing test as an algesiometer in mice. In addition, the involvement of opioid receptors in the interaction was studied using naltrexone, a non-selective opioid receptor antagonist. The administration of paracetamol or tramadol induced a dose-dependent antinociceptive activity in the assay. The dose–response curves were characterized by equal efficacy but different potencies, being i.t. paracetamol 11.84 times more potent than i.p. paracetamol, and i.t. tramadol 3.54 times more potent than the i.p. tramadol. The isobolographic analysis indicates a synergistic interaction between the coadministration of i.p. or i.t. paracetamol with tramadol. The interaction index values were similar for the i.p. and i.t. coadministration with values of 0.414 and 0.364, respectively. The different mechanisms of action of paracetamol and tramadol strongly explain the analgesic synergism between them, in agreement with the general theory of drug interaction. This synergic interaction was not modified by the non selective opioid antagonist, naltrexone. This association could be of clinical significance in the treatment of pain with a reduction of doses and adverse effects. [Copyright &y& Elsevier]

Abstract: Prevention is the best resistance management strategy in integrated vector control programs. Combined use of insecticides of different classes that interact synergistically and show multi-site actions within the insect is recognized as a potential key strategy to be implemented even before the onset of resistance. The present study is aimed at harvesting the benefits of synergism between the wild-type Bacillus thuringiensis subsp. israelensis-H14 (Bti) and Bacillus sphaericus-2362 (Bs) strains by evaluating six different combinations of mixtures toxic to Aedes and Culex mosquito larvae. Isobolographic analysis was performed to distinguish the synergistic combinations of Bti and Bs, followed by determination of the degree of synergism through synergy and improvement factors. Furthermore, the speed of activity of Bs when combined with Bti is studied by histopathological investigations on the fate of midgut muscles of mosquito larvae upon exposure to individual wild-type strains as well as their mixtures. [Copyright &y& Elsevier]

The aggregation of the amyloid-β-peptide (AβP) into well-ordered fibrils has been considered as the key pathological marker of Alzheimer's disease. Molecular attributes related to the specific binding interactions, covalently and non-covalently, of a library of compounds targeting of conformational scaffolds were computed employing static lattice atomistic simulations and array constructions. A combinatorial approach using isobolographic analysis was stochastically modeled employing Artificial Neural Networks and a Design of Experiments approach, namely an orthogonal Face-Centered Central Composite Design for small molecules, such as curcumin and glycosylated nornicotine exhibiting concentration-dependent behavior on modulating AβP aggregation and oligomerization. This work provides a mathematical and in silico approach that constitutes a new frontier in providing neuroscientists with a template for in vitro and in vivo experimentation. In future this could potentially allow neuroscientists to adopt this in silico approach for the development of novel therapeutic interventions in the neuroprotection and neurotherapy of Alzheimer's disease. In addition, the neuroprotective entities identified in this study may also be valuable in this regard. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to evaluate the nature of the antinociceptive interaction among dexketoprofen (DEX), a mixed inhibitor of the cyclo-oxygenases, and tramadol (TRAM), a weak opioid with monoaminergic activity that inhibits norepinephrine and serotonin re-uptake. We assessed antinociception in the acetic acid writhing test, the tail flick and the formalin (FT) tests, and gastrointestinal transit (GIT) after the administration of a charcoal meal. The analysis of the interaction was carried out using isobolograms and interaction indexes or the fixed-dose method GIT. The administration of DEX or TRAM individually induced dose–dependent antinociception in all the algesiometric tests. In the three tests, TRAM was between 5.2 (FT, phase I) and 35 times (FT, Phase II) more potent than DEX. When testing combinations at different potency ratios (1 : 1, 1 : 3, 3 : 1), we could demonstrate synergy in all algesiometric tests, only when drugs were combined in a 1 : 1 proportion. Interestingly, the proportion of the drugs in the combination could change the type of interaction from synergy to antagonism. On the inhibition of GIT, a dose-related inhibition was established for TRAM, but not for DEX. Using a fixed-dose protocol, we could demonstrate antagonism between DEX and TRAM on the inhibition of GIT. The results of the present study suggest that a combination of DEX and TRAM in a 1 : 1 proportion could be adequate to use in future clinical trials in humans. [ABSTRACT FROM AUTHOR]

Background and Purpose: Spinal N-methyl-D-aspartate (NMDA) receptor/cyclooxygenase (COX) and nitric oxide synthase (NOS) pathways play a major role in nociceptive processing, and influencing them simultaneously may induce synergistic analgesia. This study determined the spinal antinociceptive interactions between ketamine (NMDA receptor channel blocker), ketoprofen (COX inhibitor) and L-NAME (NOS inhibitor) combinations.Experimental Approach: Using an in vitro neonatal rat spinal cord preparation, two A-fibre-mediated reflexes, the monosynaptic reflex (MSR) and the low-intensity excitatory postsynaptic potential (epsp), and one C-fibre-mediated reflex, the high-intensity epsp, were evoked electrically. The effect of drugs and drug combinations on these reflexes was assessed and the type of interaction determined by isobolographic analysis.Key Results: Infusion of ketamine alone decreased all three reflexes. That of ketoprofen decreased both the low and the high-intensity epsp only. Infusion of L-NAME alone produced no significant effects. Co-infusion of fixed ratios of IC(40) fractions of both (ketamine+ketoprofen) and (ketamine+L-NAME) were synergistic for depressing the low and the high-intensity epsps. The interaction was sub-additive for both combinations on the MSR. The only significant effect for the (ketoprofen+L-NAME) combination was synergism on the high-intensity epsp.Conclusions and Implications: All three combinations synergistically depressed nociceptive spinal transmission, and both ketamine and ketoprofen and ketamine and L-NAME combinations did so with potentially decreased motor side effects. If such combination profiles also occur in vivo, the present findings raise the possibility of ultimate therapeutic exploitation of increased analgesia with fewer side effects. [ABSTRACT FROM AUTHOR]

Non-steroidal anti-inflammatory drugs (NSAIDs) and opioids are the most commonly used analgesics in the management of acute and chronic pain. Combined use of NSAIDs and opioids has been indicated for achieving better analgesia with reduced side effects. The present study was aimed at evaluating the combination of different NSAIDs, which inhibit cyclooxygenase (COX) enzymes and tramadol against acetic acid-induced writhing in mice. The expected beneficial effect of combination regimen was analyzed by isobolographic analysis. The oral and intrathecally administered tramadol, a μ-opioid and naproxen, a nonselective COX inhibitor produced dose-dependent antinociception, however, rofecoxib, a selective COX-2 inhibitor lacked analgesic efficacy in writhing test. Isobolographic analysis showed synergistic or supra-additive interactions for the combinations of naproxen and tramadol after oral and intrathecal administration. However, similar interaction was not observed when tramadol was combined with rofecoxib. Pretreatment with naloxone partially reversed the antinociceptive effect of tramadol per se and its combination with naproxen without modifying the per se effect of NSAID. The results demonstrated marked synergistic interaction between naproxen and tramadol and such interaction involved opioid as well as non-opioid mechanisms of tramadol and inhibition of COX-1 but not COX-2 by naproxen. [Copyright &y& Elsevier]

Opioids are the first-line treatment for cancer pain. Incomplete pain relief and the high rate of adverse effects of these compounds bring a need to combine them with other drugs acting on different targets. We here evaluate the antinociceptive interaction and adverse events of methadone combined with recombinant Phα1β, an analgesic toxin from Phoneutria nigriventer. Melanoma was produced by intraplantar inoculation of B16-F10 cells into the right paw. von Frey filaments measured the paw-withdrawal threshold after administration of methadone, Phα1β, and their combination. The degree of interaction was evaluated using isobolographic analysis. Spontaneous performance and forced motor performance were assessed with the open-field and rotarod tests, respectively. Intestinal function was evaluated by the distance traveled by charcoal and opioid tolerance was induced by daily morphine injections. Co-administration of Phα1β with methadone synergistically reverses the melanoma-induced mechanical hypersensitivity. No motor alterations were observed but mild alterations on intestinal function after treatment with the combination that was also capable of restoring morphine analgesia in the tail-flick test after an opioid-induced tolerance. Combinatorial treatment with Phα1β and methadone produces synergistic analgesic potentiation with potential implications to pain treatment even under opioid tolerance conditions. [ABSTRACT FROM AUTHOR]

Although nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the main types of drugs used to treat pain, they have several adverse effects, and such effects can be reduced by combining two analgesic drugs. The aim of this study was to evaluate the nociceptive activity of methyleugenol combined with either diclofenac or ketorolac, and determine certain parameters of pharmacokinetics. For the isobolographic analysis, the experimental effective dose 30 (ED30) was calculated for the drugs applied individually. With these effective doses, the peak plasma concentration (Cmax) was found and the other parameters of pharmacokinetics were established. Methyleugenol plus diclofenac and methyleugenol plus ketorolac decreased licking behavior in a dose-dependent manner in phase II, with an efficacy of 32.9 ± 9.3 and 39.8 ± 9.6%, respectively. According to the isobolographic analysis, the experimental and theoretical ED30 values were similar for methyleugenol plus diclofenac, suggesting an additive effect, but significantly different for methyleugenol plus ketorolac (3.6 ± 0.5 vs. 7.7 ± 0.6 mg/kg, respectively), indicating a probable synergistic interaction. Regarding pharmacokinetics, the only parameter showing a significant difference was Cmax for the methyleugenol plus diclofenac combination. Even with this difference, the combinations studied may be advantageous for treating inflammatory pain, especially for the combination methyleugenol plus ketorolac. [ABSTRACT FROM AUTHOR]

Post-traumatic seizures during the emergent state of traumatic brain injury (TBI) are deemed detrimental to the recovery of TBI patients. Phenytoin (PHT) and levetiracetam (LEV) are the commonly prescribed drugs as prophylaxis. Although LEV has become more favorable than PHT owing to its improved safety profile, many patients are still intractable to the monotherapy of either drug. In this study we applied the isobolographic approach to evaluate PHT + LEV combination therapy against penetrating ballistic-like brain injury (PBBI) induced nonconvulsive seizures (NCS) in rats, aimed at achieving synergism with properly paired dose ratios of the two drugs. NCS were induced by PBBI and detected by EEG recording for 72 h. PHT and LEV were tested at the following dose ratios (PHT/LEV): 1.8/6.3, 3.6/12.7, 7.2/25.4, or 14.5/50.7 mg/kg, which were derived from previous monotherapy results of each drug. Treatments were given intravenously twice/day for three days. Control animals received matching vehicle treatments. The results showed that except for the lowest dose ratio, PHT + LEV combination therapy significantly reduced NCS frequency and total seizure duration by 61%-84% across the three high dose ratios (as compared to vehicle treatments). The highest dose ratio also significantly reduced NCS incidence from 65% (Vehicle) to 25% and delayed NCS latency from 39 h (vehicle) to 57 h post-injury. The dose equivalent analysis of the isobolographic design indicated an achievement of synergism because the observed effects across all dose ratios exceeded the expected additive effects. Compared to our previous results of a PHT or LEV monotherapy derived from the identical TBI, the combined treatments of PHT + LEV outperformed the monotherapy of each individual drug by achieving statistically defined synergism. Critically, the doses of each drug used in combination were 2-3 fold lower than the monotherapy doses required of each drug, which may alleviate the safety concerns of these drugs used in TBI patients. [ABSTRACT FROM AUTHOR]