Synergy, Additivity and Antagonism between Esculetin and Six Commonly Used Chemotherapeutics in Various Malignant Melanoma Cell Lines-An Isobolographic Analysis.

(1) Malignant melanomas are dangerous skin cancers, and the treatment of melanomas with various cytostatic drugs often causes side effects and after their prolonged use resistance to these drugs appears. The aim of this study was to evaluate the anticancer effects of esculetin (a simple coumarin) and to assess pharmacodynamic interactions between esculetin and six commonly used cytostatic drugs (cisplatin, epirubicin, docetaxel, paclitaxel, mitoxantrone and vemurafenib) using an isobolographic analysis. (2) The experiments were carried out on four human malignant melanoma cell lines (FM55P, A375, FM55M2 and SK-MEL28). The effects of esculetin on viability, cell proliferation and cytotoxicity were verified in the range of concentrations of 2-200 µM. (3) Esculetin inhibited, in a dose-dependent manner, malignant melanoma cell viability and proliferation. The IC50 for esculetin ranged from 18.20 ± 2.93 to 120.64 ± 30.39 µM depending on the melanoma cell lines used. The combinations of esculetin with epirubicin and vemurafenib showed antagonistic interactions, the combinations of esculetin with cisplatin, docetaxel and paclitaxel showed additive interactions. For the combinations of esculetin with mitoxantrone, the isobolographic analysis displayed synergy. (4) In the treatment of malignant melanoma, esculetin should not be combined with epirubicin or vemurafenib, due to the reduction of their anticancer effects, while the synergistic interactions (esculetin + mitoxantrone) deserve a preclinical recommendation as a beneficial combination during anticancer therapy.

Ranolazine Interacts Antagonistically with Some Classical Antiepileptic Drugs-An Isobolographic Analysis.

Ranolazine, an antianginal and antiarrhythmic drug blocking slow inactivating persistent sodium currents, is described as a compound with anticonvulsant potential. Since arrhythmia often accompanies seizures, patients suffering from epilepsy are frequently co-treated with antiepileptic and antiarrhythmic drugs. The aim of this study was to evaluate the effect of ranolazine on maximal-electroshock (MES)-induced seizures in mice as well as interactions between ranolazine and classical antiepileptic drugs in this model of epilepsy. Types of pharmacodynamic interactions were established by isobolographic analysis of obtained data. The main findings of the study were that ranolazine behaves like an antiseizure drug in the MES test. Moreover, ranolazine interacted antagonistically with carbamazepine, phenytoin, and phenobarbital in the proportions of 1:3 and 1:1. These interactions occurred pharmacodynamic, since ranolazine did not change the brain levels of antiepileptic drugs measured in the fluorescence polarization immunoassay. Ranolazine and its combinations with carbamazepine, phenytoin, and phenobarbital did not impair motor coordination evaluated in the chimney test. Unfortunately, an attempt to conduct a passive avoidance task (evaluating long-term memory) resulted in ranolazine-induced delayed lethality. In conclusion, ranolazine exhibits clear-cut anticonvulsant properties in the MES test but interacts antagonistically with some antiepileptic drugs. The obtained results need confirmation in clinical studies. The mechanisms of ranolazine-induced toxicity require specific explanation.

Fiber Preparation from Micronized Oat By-Products: Antioxidant Properties and Interactions between Bioactive Compounds.

This study aimed to investigate the possibility of utilizing oat by-products for fiber preparation. Oat husk (OH) and oat bran (OB) were micronized and used to prepare a novel product rich in fiber and with enhanced antioxidant properties. The basic chemical composition and phenolic acid profile were determined in OH and OB. The antioxidant properties of OH and OB were also analyzed. The type and strength of interactions between the biologically active compounds from their mixtures were characterized by an isobolographic analysis. The analyses showed that the sum of phenolic acids was higher in OH than in OB. Ferulic acid was dominant in both OH and OB; however, its content in OH was over sixfold higher than that in OB. The results also suggested that both OH and OB can be used for preparing fiber with enhanced antioxidant properties. The optimal composition of the preparation, with 60-70% of OH and 30-40% of OB, allows for obtaining a product with 60-70% fiber and enhanced antioxidant activity due to bioactive substances and their synergistic effect. The resulting product can be a valuable additive to various food and dietary supplements.

Xylopic acid-amodiaquine and xylopic acid-artesunate combinations are effective in managing malaria in Plasmodium berghei-infected mice.

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.

Synergistic protective effects between docosahexaenoic acid and omeprazole on the gastrointestinal tract in the indomethacin-induced injury model.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most commonly used drugs due to their antipyretic, anti-inflammatory, and analgesic properties. However, NSAIDs can cause adverse reactions, mainly gastrointestinal damage. Omeprazole (OMP) exhibits gastroprotective activity, but its protection is limited at the intestinal level. For this reason, it is essential to utilize a combination of therapies that provide fewer adverse effects, such as the combined treatment of OMP and docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid with anti-inflammatory, analgesic, and gastroprotective activities. The objective of this study was to evaluate the pharmacological interaction between DHA and OMP in a murine model of indomethacin-induced gastrointestinal damage. The gastroprotective and enteroprotective effects of DHA (0.3-10 mg/kg, p.o.), OMP (1-30 mg/kg, p.o.), or the combination treatment of both compounds (3-56.23 mg/kg, p.o.) were evaluated in the indomethacin-induced gastrointestinal damage model (30 mg/kg, p.o.). Since DHA and OMP exhibited a protective effect in a dose-responsive fashion, the ED30 for each individual compound was determined and a 1:1 combination of DHA and OMP was tested. Isobolographic analysis was used to determine any pharmacodynamic interactions. Since the effective experimental dose ED30 (Zexp) of the combined treatment of DHA and OMP was lower than the theoretical additive dose (Zadd; p < .05) in both the stomach and small intestine their protective effects were considered synergistic. These results indicate that the synergistic protective effects from combined treatment of DHA and OMP could be ideal for mitigating damage generated by NSAIDs at the gastrointestinal level.

Synergistic interaction between B vitamins and statins to counter nociception in rats.

Evidence suggests that the antinociceptive activity of various drugs can be increased when administered in combination with B vitamins (BVs). The aim of this study was to examine the potential interaction between statins and BVs to counter nociception, the latter measured by the formalin test. Rats were orally administered atorvastatin (1, 3, 10 and 30 mg/kg), pravastatin (1, 3, 10 and 30 mg/kg), rosuvastatin (1, 3, 10 and 30 mg/kg), BVs (31, 56, 100 and 180 mg/kg) or calculated combinations of BVs with each drug. The effective dose 30 (ED30 ) was calculated for each statin and BVs and subjected to isobolographic analysis, thus finding the ED30 of the combinations. The antinociceptive experimental ED30 values for BVs administered with atorvastatin, pravastatin or rosuvastatin were 1.53 ± 0.38, 6.74 ± 0.04 and 4.26 ± 0.39, respectively, being lower (p < .05) than the corresponding theoretical ED30 : 28.02 ± 2.20, 28.17 ± 2.20 and 29.86 ± 2.21. Since BVs likely boost the antinociceptive effect of statins, these combinations could possibly be advantageous in pain management.

Antagonistic Interaction between Histone Deacetylase Inhibitor: Cambinol and Cisplatin-An Isobolographic Analysis in Breast Cancer In Vitro Models.

Breast cancer (BC) is the leading cause of death in women all over the world. Currently, combined chemotherapy with two or more agents is considered a promising anti-cancer tool to achieve better therapeutic response and to reduce therapy-related side effects. In our study, we demonstrated an antagonistic effect of cytostatic agent-cisplatin (CDDP) and histone deacetylase inhibitor: cambinol (CAM) for breast cancer cell lines with different phenotypes: estrogen receptor positive (MCF7, T47D) and triple negative (MDA-MB-231, MDA-MB-468). The type of pharmacological interaction was assessed by an isobolographic analysis. Our results showed that both agents used separately induced cell apoptosis; however, applying them in combination ameliorated antiproliferative effect for all BC cell lines indicating antagonistic interaction. Cell cycle analysis showed that CAM abolished cell cycle arrest in S phase, which was induced by CDDP. Additionally, CAM increased cell proliferation compared to CDDP used alone. Our data indicate that CAM and CDDP used in combination produce antagonistic interaction, which could inhibit anti-cancer treatment efficacy, showing importance of preclinical testing.

Interactions among Lacosamide and Second-Generation Antiepileptic Drugs in the Tonic-Clonic Seizure Model in Mice.

Combination therapy with two or three antiseizure medications (ASMs) is sometimes a preferred method of treatment in epilepsy patients. (1) Background: To detect the most beneficial combination among three ASMs, a screen test evaluating in vivo interactions with respect to their anticonvulsant properties, was conducted on albino Swiss mice; (2) Methods: Classification of interactions among lacosamide (LCM) and selected second-generation ASMs (lamotrigine (LTG), pregabalin (PGB), oxcarbazepine (OXC), and topiramate (TPM)) was based on the isobolographic analysis in the mouse maximal electroshock-induced seizure (MES) model. Interactions among LCM and second-generation ASMs were visualized using a polygonogram; (3) Results: In the mouse MES model, synergy was observed for the combinations of LCM + TPM + PGB and LCM + OXC + PGB. Additivity was reported for the other combinations tested i.e., LCM + LTG + TPM, LCM + LTG + PGB, LCM + LTG + OXC, and LCM + OXC + TPM in this seizure model. No adverse effects associated with triple ASM combinations, containing LCM and second-generation ASMs were observed in mice; (4) Conclusions: The combination of LCM + TPM + PGB was the most beneficial combination among the tested in this study, offering synergistic suppression of tonic-clonic seizures in mice subjected to the MES model. Both the isobolographic analysis and polygonogram method can be recommended for experimental epileptology when classifying interactions among the ASMs.

Some Dietary Phenolic Compounds Can Activate Thyroid Peroxidase and Inhibit Lipoxygenase-Preliminary Study in the Model Systems.

The presented research concerns the triple activity of trans-cinnamic (tCA), ferulic (FA) and syringic acids (SA). They act as thyroid peroxidase (TPO) activators, lipoxygenase (LOX) inhibitors and show antiradical activity. All compounds showed a dose-dependent TPO activatory effect, thus the AC50 value (the concentration resulting in 50% activation) was determined. The tested compounds can be ranked as follows: tCA > FA > SA with AC50 = 0.10, 0.39, 0.69 mM, respectively. Strong synergism was found between FA and SA. The activatory effects of all tested compounds may result from interaction with the TPO allosteric site. It was proposed that conformational change resulting from activator binding to TPO allosteric pocket results from the flexibility of a nearby loop formed by residues Val352-Tyr363. All compounds act as uncompetitive LOX inhibitors. The most effective were tCA and SA, whereas the weakest was FA (IC50 = 0.009 mM and IC50 0.027 mM, respectively). In all cases, an interaction between the inhibitors carboxylic groups and side-chain atoms of Arg102 and Arg139 in an allosteric pocket of LOX was suggested. FA/tCA and FA/SA acted synergistically, whereas tCA/SA demonstrated antagonism. The highest antiradical activity was found in the case of SA (IC50 = 0.22 mM). FA/tCA and tCA/SA acted synergistically, whereas antagonism was found for the SA/FA mixture.

Sensitization of MCF7 Cells with High Notch1 Activity by Cisplatin and Histone Deacetylase Inhibitors Applied Together.

Histone deacetylase inhibitors (HDIs) are promising anti-cancer agents that inhibit proliferation of many types of cancer cells including breast carcinoma (BC) cells. In the present study, we investigated the influence of the Notch1 activity level on the pharmacological interaction between cisplatin (CDDP) and two HDIs, valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA, vorinostat), in luminal-like BC cells. The type of drug-drug interaction between CDDP and HDIs was determined by isobolographic analysis. MCF7 cells were genetically modified to express differential levels of Notch1 activity. The cytotoxic effect of SAHA or VPA was higher on cells with decreased Notch1 activity and lower for cells with increased Notch1 activity than native BC cells. The isobolographic analysis demonstrated that combinations of CDDP with SAHA or VPA at a fixed ratio of 1:1 exerted additive or additive with tendency toward synergism interactions. Therefore, treatment of CDDP with HDIs could be used to optimize a combined therapy based on CDDP against Notch1-altered luminal BC. In conclusion, the combined therapy of HDIs and CDDP may be a promising therapeutic tool in the treatment of luminal-type BC with altered Notch1 activity.

Palmatine, a Bioactive Protoberberine Alkaloid Isolated from Berberis cretica, Inhibits the Growth of Human Estrogen Receptor-Positive Breast Cancer Cells and Acts Synergistically and Additively with Doxorubicin.

Palmatine (PLT) is a natural isoquinoline alkaloid that belongs to the class of protoberberines and exhibits a wide spectrum of pharmacological and biological properties, including anti-cancer activity. The aim of our study was to isolate PLT from the roots of Berberis cretica and investigate its cytotoxic and anti-proliferative effects in vitro alone and in combination with doxorubicine (DOX) using human ER+/HER2- breast cancer cell lines. The alkaloid was purified by column chromatography filled with silica gel NP and Sephadex LH-20 resin developed in the mixture of methanol: water (50:50 v/v) that provided high-purity alkaloid for bioactivity studies. The purity of the alkaloid was confirmed by high resolution mass measurement and MS/MS fragmentation analysis in the HPLC-ESI-QTOF-MS/MS-based analysis. It was found that PLT treatment inhibited the viability and proliferation of breast cancer cells in a dose-dependent manner as demonstrated by MTT and BrdU assays. PLT showed a quite similar growth inhibition on breast cancer cells with IC50 values ranging from 5.126 to 5.805 µg/mL. In contrast, growth of normal human breast epithelial cells was not affected by PLT. The growth inhibitory activity of PLT was related to the induction of apoptosis, as determined by Annexin V/PI staining. Moreover, PLT sensitized breast cancer cells to DOX. Isobolographic analysis revealed synergistic and additive interactions between studied agents. Our studies suggest that PLT can be a potential candidate agent for preventing and treating breast cancer.

Analgesia additive interaction between tadalafil and morphine in an experimental animal model.

Since both morphine and tadalafil have been proven to exert some of their analgesic activity through modulation of the NO-cGMP pathway, the aim of the current study is to evaluate the pharmacologic interaction between tadalafil and morphine to decrease the dose of morphine and subsequently its side effects. The assessment was carried out through isobolographic analysis relative to ED50s of both morphine and tadalafil obtained by tail-flick test on BALB/c mice. Morphine and tadalafil ED50s calculated from the dose-response curves were 8303 and 2080 µg/kg, respectively. The experimental ED50 values of morphine and tadalafil in their mixture were 4800 and 1210 µg/kg, respectively. Those results showed an additive interaction between morphine and tadalafil presented by a total fraction value for the mixture of 1160 µg/kg. This outcome can be interpreted by the fact that both drugs share common pathways, namely, NO-cGMP and opioid receptors. As a conclusion, the morphine and tadalafil combination showed an additive effect against acute pain, which is mediated through the central nervous system, thus providing a rationale for combining them to decrease morphine dose and thus minimizing its side effects.

Synergistic interaction between 4-allyl-1-hydroxy-2-methoxybenzene (eugenol) and diclofenac: An isobolograpic analysis in Wistar rats.

Clinical and preclinical research that contributes pain palliation has suggested that drugs favor the expected effects and minimize the adverse effects. Among the most widely used strategies is the combination of analgesic drugs among those in the same group, with those in another group of analgesics or with co-adjuvants (nonanalgesic drugs or elements of traditional medicine). This work aims to evaluate the interaction between eugenol (EUG) and diclofenac (DFC) on nociception in the presence of a noxious stimulus through the formalin test and isobolographic analysis. The results indicate that EUG, DFC, or the combination of both produce an antinociceptive effect in rodents (p ≤ 0.05). Local co-administration of EUG and DFC gave a theoretical effective dose (Zadd ) 2,936.27 ± 155.33 µg/kg (p ≤ 0.05) significantly higher as compared to the effective experimental doses (Zmix ) of 866.89 ± 0.02 µg/kg in phase 1 and 292.88 ± 0.05 µg/kg in phase 2, with an interaction index of 0.29 and 0.09, respectively. These data allow concluding that the interaction derived from the joint administration of EUG and DFC, in the rodent at a local level, is synergistic.

Synergistic or Additive Pharmacological Interactions between Magnoflorine and Cisplatin in Human Cancer Cells of Different Histological Origin.

Magnoflorine is an aporphine alkaloid present in plant species belonging to the Berberidaceae, Magnoliaceae, Menispermaceae, or Papaveraceae botanical families. The interest of magnoflorine has increased recently due to its multiplicity of pharmacological properties. The aim of this study was the analysis of combined anti-proliferative effect of magnoflorine and cisplatin and the assessment of drug-drug pharmacological interaction between these agents using isobolographic method in MDA-MB-468 human breast, NCIH1299 lung, TE671 rhabdomyosarcoma, or T98G glioblastoma cancer cell lines. Magnoflorine in combination with cisplatin at a fixed ratio of 1:1 augmented their anticancer action and yielded synergistic or additive pharmacological interactions by means of isobolographic method, therefore combined therapy using these two active agents can be a promising chemotherapy regimen in the treatment of some types of breast, lung, rhabdomyosarcoma, and glioblastoma cancers.

Antinociceptive Interaction and Pharmacokinetics of the Combination Treatments of Methyleugenol Plus Diclofenac or Ketorolac.

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.

Pharmacodynamic interaction of 3α-hydroxymasticadienonic acid and diligustilide against indomethacin-induced gastric damage in rats.

The aims of the study were to evaluate the pharmacodynamic interaction between 3α-hydroxymasticadienonic acid and diligustilide (DLG), isolated from the plants Amphiptherygium adstringens and Ligusticum porteri, respectively, using the indomethacin-induced gastric injury model, as well as their individual gastroprotective efficacy in this model. Male Wistar rats were orally administered with 3α-hydroxymasticadienonic acid, DLG or the mixture of 3α-hydroxymasticadienonic acid-DLG (at a fixed-ratio combination of 1:1, 1:3, and 3:1). Thirty minutes later, the gastric damage was induced by a single oral dose of indomethacin (30 mg/kg). Three hours later, the gastric injury (mm2 ) was determined. 3α-hydroxymasticadienonic acid and DLG as individual compounds showed a gastroprotective effect against indomethacin-induced gastric damage (p < .05). The effective dose (ED50 ) values for each compound were 6.96 ± 1.25 mg/kg for 3α-hydroxymasticadienonic acid and 2.63 ± 0.37 mg/kg for DLG. The isobolographic analysis performed showed that the combination exhibited super-additive interaction as the experimental ED50 values (Zexp) were lower than theoretical additive dose values (Zadd; p < .05). Our results identify the super-additive (synergist) interaction between 3α-hydroxymasticadienonic acid and DLG and the gastric safety of both compounds in the indomethacin-induced gastric injury model, suggesting their potential in the future as a strategy to decrease the gastric damage associated to the chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs).

Additive Pharmacological Interaction between Cisplatin (CDDP) and Histone Deacetylase Inhibitors (HDIs) in MDA-MB-231 Triple Negative Breast Cancer (TNBC) Cells with Altered Notch1 Activity-An Isobolographic Analysis.

The aim of this study was to investigate the influence of the Notch1 activity level on the pharmacological interaction between cisplatin (CDDP) and two histone deacetylase inhibitors (HDIs)-valproic acid (VPA) and vorinostat (SAHA) in the triple negative breast cancer (TNBC) cells. Stable breast cancer (BC) cell lines with increased and decreased activity of Notch1 were generated using a transfection method. The type of interaction between CDDP and the HDIs was determined by isobolographic analysis of cell proliferation in MDA-MB-231 cells with differential levels of Notch1 activity in vitro. The combination of CDDP/SAHA and CDDP/VPA in the MDA-MB-231 triple negative breast cancer (TNBC) cells with increased activity of Notch1, as well as CDDP/VPA in the MDA-MB-231 cells with decreased activity of Notch1, yielded an additive interaction, whereas additivity with a tendency towards antagonism was observed for the combination of CDDP/SAHA in MDA-MB-231 cells with the decreased activity of Notch1. Our studies demonstrated that SAHA and VPA might be considered as potential therapeutic agents in combination therapy with CDDP against TNBC with altered Notch1 activity.

Beneficial Combination of Lacosamide with Retigabine in Experimental Animals: An Isobolographic Analysis.

BACKGROUND/AIM: To isobolographically determine the types of interactions that occur between retigabine and lacosamide (LCM; two third-generation antiepileptic drugs) with respect to their anticonvulsant activity and acute adverse effects (sedation) in the maximal electroshock-induced seizures (MES) and chimney test (motor performance) in adult male Swiss mice. METHODS: Type I isobolographic analysis for nonparallel dose-response effects for the combination of retigabine with LCM (at the fixed-ratio of 1:1) in both the MES and chimney test in mice was performed. Brain concentrations of retigabine and LCM were measured by high-pressure liquid chromatography (HPLC) to characterize any pharmacokinetic interactions occurring when combining these drugs. RESULTS: Linear regression analysis revealed that retigabine had its dose-response effect line nonparallel to that of LCM in both the MES and chimney tests. The type I isobolographic analysis illustrated that retigabine combined with LCM (fixed-ratio of 1:1) exerted an additive interaction in the mouse MES model and sub-additivity (antagonism) in the chimney test. With HPLC, retigabine and LCM did not mutually change their total brain concentrations, thereby confirming the pharmacodynamic nature of the interaction. CONCLUSION: LCM combined with retigabine possesses a beneficial preclinical profile (benefit index ranged from 2.07 to 2.50) and this 2-drug combination is worth recommending as treatment plan to patients with pharmacoresistant epilepsy.

Isobolographic Analyses of Proglumide-Celecoxib Interaction in Rats with Painful Diabetic Neuropathy.

Preclinical Research The aim of the present study was to analyze the antihyperalgesic and antiallodynic interaction between the non-selective cholecystokinin (CCK) antagonist receptor, proglumide, and the selective cyclooxygenase-2 inhibitor, celecoxib in streptozotocin (STZ)-induced diabetic rats. Hyperalgesia was evaluated in the formalin test and tactile allodynia using von Frey filaments. Isobolographic analyses were employed to define the nature of the compound interactions, using a fixed dose ratio (0.5:0.5). Proglumide (20-160 mg/kg) and celecoxib (0.3-30 mg/kg) in these fixed dose ratio combinations induced dose-dependent antihyperalgesia and an antiallodynic effect in diabetic rats. ED40 values were calculated for the treatments and an isobologram was constructed. Theoretical ED40 values for combination proglumide-celecoxib estimated from the isobolograms for antihyperalgesic and antiallodynic activity (30.50 ± 1.90 mg/kg and 45.81 ± 4.55 mg/kg, respectively) were obtained, while experimental ED40 values for this antihyperalgesic and antiallodynic combined effect (13.83 ± 0.65 mg/kg and 17.74 ± 3.57 mg/kg; respectively) were significantly different. Coadministration of proglumide-celecoxib showed an interaction index value of 0.45 ± 0.03 for the antihyperalgesic effect and 0.39 ± 0.08 for the antiallodynic activity, indicating a synergistic interaction. These data suggest that proglumide and celecoxib can interact synergistically to reduce hyperalgesic and allodynic behaviors in diabetic neuropathy. This combination could be useful to treat neuropathic pain in diabetic patients. Drug Dev Res 78 : 116-123, 2017. ©2017 Wiley Periodicals, Inc.

Synergism between Naproxen and Rutin in a Mouse Model of Visceral Pain.

Preclinical Research The aim of the present study was to evaluate the antinociceptive interaction between naproxen and the glycoside flavonoid, rutin in the acetic acid-induced writhing test in mice. Naproxen (5, 20, 50, and 100 mg/kg p.o.) or rutin (10, 25, 50, and 100mg/kg p.o.) were administered 60 min before the intraperitoneal administration with acetic acid. The dose-response curve of each individual compound and the experimental effective dose 50 (ED50 ) value were obtained to determinate different proportions of the combinations between the two compounds (naproxen-rutin 1:1, 3:1, and 3:1) in the writhing test. The results indicated a synergistic antinociceptive interaction between two drugs with different mechanism of action, naproxen and rutin in all the combinations. Drug Dev Res 78 : 184-188, 2017. © 2017 Wiley Periodicals, Inc.