Antiepileptic drugs as analgesics/adjuvants in inflammatory pain: current preclinical evidence.

Inflammatory pain is the most common type of pain that is treated clinically. The use of currently available treatments (classic analgesics - NSAIDs, paracetamol and opioids) is limited by insufficient efficacy and/or side effects/tolerance development. Antiepileptic drugs (AEDs) are widely used in neuropathic pain treatment, but there is substantial preclinical evidence on their efficacy against inflammatory pain, too. In this review we focus on gabapentinoids (gabapentin and pregabalin) and dibenzazepine AEDs (carbamazepine, oxcarbazepine, and recently introduced eslicarbazepine acetate) and their potential for relieving inflammatory pain. In models of somatic, visceral and trigeminal inflammatory pain, that have a translational value for inflammatory conditions in locomotor system, viscera and head/face, AEDs have demonstrated analgesic activity. This activity was mostly consistent, dependent on the dose and largely independent on the site of inflammation and method of its induction, nociceptive stimuli, species, specific drug used, its route of administration and dosing schedule. AEDs exerted comparable efficacy with classic analgesics. Effective doses of AEDs are lower than toxic doses in animals and, when expressed as equivalent human doses, they are largely overlapping with AEDs doses already used in humans for treating epilepsy/neuropathic pain. The main mechanism of antinociceptive/antihyperalgesic action of gabapentinoids in inflammatory pain models seems to be α2δ-dependent suppression of voltage-gated calcium channels in primary sensory neurons that leads to reduced release of neurotransmitters in the spinal/medullar dorsal horn. The suppression of NMDA receptors via co-agonist binding site primarily at spinal sites, activation of various types of K+ channels at spinal and peripheral sites, and activation of noradrenergic and serotonergic descending pain modulatory pathways may also contribute. Inhibition of voltage-gated sodium channels along the pain pathway is probably the main mechanism of antinociceptive/antihyperalgesic effects of dibenzazepines. The recruitment of peripheral adrenergic and purinergic mechanisms and central GABAergic mechanisms may also contribute. When co-administered with classic/other alternative analgesics, AEDs exerted synergistic/additive interactions. Reviewed data could serve as a basis for clinical studies on the efficacy/safety of AEDs as analgesics/adjuvants in patients with inflammatory pain, and contribute to the improvement of the treatment of various inflammatory pain states.

Levetiracetam synergizes with gabapentin, pregabalin, duloxetine and selected antioxidants in a mouse diabetic painful neuropathy model.

RATIONALE: We have reported that levetiracetam, a novel anticonvulsant with analgesic properties, synergizes with ibuprofen/aspirin/paracetamol in a model of diabetic painful neuropathy (DPN). Most guidelines recommend gabapentin, pregabalin, and duloxetine as first- or second-line agents for DPN. OBJECTIVE: We examined the effects of combination treatment of first-/second-line analgesics with levetiracetam in a model of DPN. Additionally, the levetiracetam's combinations with antioxidants, low dose of aspirin, coenzyme Q10, or α-lipoic acid were evaluated. METHODS: Diabetes was induced in C57BL/6 mice with a single high dose of streptozotocin. The antinociceptive effects of orally administered levetiracetam, gabapentin, pregabalin, duloxetine (acute treatment) and aspirin, coenzyme Q10, and α-lipoic acid (preventive 7-day treatment), as well as combinations of levetiracetam with individual drugs were examined in the tail-flick test. In combination experiments, the drugs were coadministered in fixed-dose fractions of single-drug ED50; the type of interaction was determined by isobolographic analysis. RESULTS: About 60-, 32-, 30-, 26-, 18-, and 6-fold reductions of doses of both drugs in levetiracetam combinations with pregabalin, gabapentin, coenzyme Q10, aspirin, duloxetine, and α-lipoic acid, respectively, were detected. CONCLUSIONS: Combinations of levetiracetam with gabapentin/pregabalin/duloxetine that target different mechanisms/sites of action involved in DPN, as well as combinations of levetiracetam and low-dose aspirin/coenzyme Q10/α-lipoic acid that target underlying causes of DPN, produce marked synergistic interactions in reducing nociception in diabetic mice. This suggests that these combination treatments might be of great benefit for diabetic patients and should be explored further in clinical trials.

Laserpitium zernyi Hayek Flower and Herb Extracts: Phenolic Compounds, and Anti-edematous, Antioxidant, and Antimicrobial Activities.

Phenolic compounds and different biological activities of the dry MeOH extracts of the flowers and the herb (aerial parts without flowers) of Laserpitium zernyi Hayek (Apiaceae) were investigated. The total phenolic contents in the extracts were determined spectrophotometrically using Folin-Ciocalteu reagent. In both extracts, apigenin, luteolin, their 7-O-glucosides, and chlorogenic acid were detected by HPLC. Identified phenolics were quantified in both extracts, except luteolin in L. zernyi herb extract. The extracts (p.o.) were tested for anti-edematous activity in a model of carrageenan (i.pl.) induced rat paw edema. Antioxidant activity of the extracts was assessed by FRAP assay and DPPH and • OH radicals scavenging tests. Antimicrobial activity was investigated using broth microdilution test against five Gram-positive and three Gram-negative bacteria, as well as against two strains of Candida albicans. The polyphenol-richer flower extract exerted higher anti-edematous and antioxidant activities. The herb extract exhibited better antimicrobial effect against Micrococcus luteus, Enterococcus faecalis, Bacillus subtilis, and Pseudomonas aeruginosa, while against other tested microorganisms, the activity of both extracts was identical. Demonstrated biological activities of L. zernyi flower and herb extracts represent a good basis for their further investigation as potential new herbal medicinal raw materials.

Levetiracetam synergises with common analgesics in producing antinociception in a mouse model of painful diabetic neuropathy.

Painful diabetic neuropathy is difficult to treat. Single analgesics often have insufficient efficacy and poor tolerability. Combination therapy may therefore be of particular benefit, because it might provide optimal analgesia with fewer adverse effects. This study aimed to examine the type of interaction between levetiracetam, a novel anticonvulsant with analgesic properties, and commonly used analgesics (ibuprofen, aspirin and paracetamol) in a mouse model of painful diabetic neuropathy. Diabetes was induced in C57BL/6 mice with a single high dose of streptozotocin, applied intraperitoneally (150 mg/kg). Thermal (tail-flick test) and mechanical (electronic von Frey test) nociceptive thresholds were measured before and three weeks after diabetes induction. The antinociceptive effects of orally administered levetiracetam, analgesics, and their combinations were examined in diabetic mice that developed thermal/mechanical hypersensitivity. In combination experiments, the drugs were co-administered in fixed-dose fractions of single drug ED50 and the type of interaction was determined by isobolographic analysis. Levetiracetam (10-100 mg/kg), ibuprofen (2-50 mg/kg), aspirin (5-75 mg/kg), paracetamol (5-100 mg/kg), and levetiracetam-analgesic combinations produced significant, dose-dependent antinociceptive effects in diabetic mice in both tests. In the tail-flick test, isobolographic analysis revealed 15-, and 19-fold reduction of doses of both drugs in the combination of levetiracetam with aspirin/ibuprofen, and paracetamol, respectively. In the von Frey test, approximately 7- and 9-fold reduction of doses of both drugs was detected in levetiracetam-ibuprofen and levetiracetam-aspirin/levetiracetam-paracetamol combinations, respectively. These results show synergism between levetiracetam and ibuprofen/aspirin/paracetamol in a model of painful diabetic neuropathy and might provide a useful approach to the treatment of patients suffering from painful diabetic neuropathy.

Antinociceptive and anti-edematous activities of the essential oils of two Balkan endemic Laserpitium species.

In this paper antinociceptive and anti-edematous effects are examined of the essential oils of the underground parts of two Balkan endemic Laserpitium species (Apiaceae), L. zernyi and L. ochridanum. Furthermore, the essential oil of the underground parts of L. ochridanum is chemically characterised by GC and GC-MS. Antinociceptive and anti-edematous effects were measured in a rat model of localized inflammation, induced by carrageenan, using apparatus for the modified paw-pressure test, and plethysmometer, respectively. The effects of both Laserpitium essential oils were measured after oral gavage administration to male Wistar rats in doses of 25, 50 and 100 mg/kg. The main constituents of L. ochridanum essential oil were: alpha-pinene (33.2%), alpha-bisabolol (10.3%) and chamazulene (14.9%). The essential oil of L. zernyi was previously shown to be rich in alpha-pinene (31.6%) and alpha-bisabolol (30.9%). Both examined essential oils produced a significant dose-dependent antinociceptive effect. The corresponding ED50 +/- SEM in producing antinociception were 45.9 +/- 4.9 mg/kg and 42.4 +/- 2.1 mg/kg for L. zernyi and L. ochridanum oil, respectively. Both essential oils also significantly reduced paw edema in a dose-dependent manner. The estimated ED50 +/- SEM values for the anti-edematous effect were 36.3 +/- 4.5 mg/kg for L. zernyi oil and 45.1 +/- 11.3 mg/kg for L. ochridanum oil. These results suggest that the essential oils of both investigated Laserpitium species may be effective against pain and edema present in various inflammatory conditions.

Antihyperalgesic and antiedematous activities of bisabolol-oxides-rich matricaria oil in a rat model of inflammation.

From the dried flower heads of Matricaria recutita L., essential oil was isolated by hydrodistillation, and in the obtained blue oil, α-bisabolol oxide A (21.5%), α-bisabolol oxide B (25.5%) and (Z)-spiroether (cis-en-yn-spiroether) (10.3%) were identified as the main compounds, by gas chromatography (GC) and GC-mass spectrometry analyses. The antihyperalgesic effects of this oil were examined in a rat model of inflammation induced by carrageenan, through a modified 'paw-pressure' test. Antiedematous effects were examined in a rat model of inflammation induced by carrageenan, dextran and histamine, through plethysmometry. Matricaria oil (25, 50 and 100 mg/kg, p.o.) exhibited a significant dose-dependent reduction of hyperalgesia and edema induced by carrageenan in both prophylactic and therapeutic treatment schemes. It was more efficacious in the prophylactic treatment scheme, and the corresponding median effective dose (ED50 ) ± standard error of the mean (SEM) values were 49.8 ± 6.0 and 42.4 ± 0.2 mg/kg for antihyperalgesic and antiedematous effects, respectively. Prophylactic treatments with matricaria oil (25, 50 and 100 mg/kg, p.o.) caused a significant dose-dependent antiedematous effect in dextran-induced edema with lower efficacy than in the carrageenan model. In a dose of 100 mg/kg, p.o., matricaria oil caused a slight reduction of histamine-induced edema. These results suggest that bisabolol-oxide-rich matricaria oil may be effective against pain and edema present in various inflammatory conditions, which supports matricaria traditional uses.

Levetiracetam interacts synergistically with nonsteroidal analgesics and caffeine to produce antihyperalgesia in rats.

UNLABELLED: Levetiracetam is a novel anticonvulsant with antihyperalgesic efficacy in inflammatory pain. Nonsteroidal analgesics and caffeine, as analgesic adjuvant, are widely used against inflammatory pain. This study characterized the manner in which levetiracetam interacts with analgesics (ibuprofen, celecoxib, and paracetamol) and caffeine to suppress hyperalgesia in a model of localized inflammation. Rat paw inflammation was induced by intraplantar carrageenan (.1 mL, 1%). Hyperalgesia and antihyperalgesic effects of levetiracetam (orally), analgesics (orally), and caffeine (intraperitoneally) alone and 2-drug combinations of levetiracetam with analgesics or caffeine were examined by a modified paw pressure test. The type of interaction between components was determined by isobolographic analysis or by analysis of the log dose-response curves for drug combination and drugs alone. Levetiracetam (10-200 mg/kg), ibuprofen (12.5-100 mg/kg), celecoxib (3.75-30 mg/kg), paracetamol (50-200 mg/kg), caffeine (15-100 mg/kg), and 2-drug combinations of levetiracetam with analgesics/caffeine produced a significant, dose-dependent reduction of inflammatory hyperalgesia. Isobolographic analysis revealed that levetiracetam exerts a synergistic interaction with analgesics, with approximately 7-, 9-, and 11-fold reduction of doses of both drugs in combination of levetiracetam with paracetamol, celecoxib, and ibuprofen, respectively. Analysis of the log dose-response curves for levetiracetam (1-50 mg/kg) in the presence of caffeine (10 mg/kg) and levetiracetam applied alone also revealed a synergistic interaction. Levetiracetam's ED50 in the presence of caffeine was reduced approximately 11-fold. PERSPECTIVE: The presented data suggest that 2-drug combinations of levetiracetam and nonsteroidal analgesics or caffeine could be useful in treatment of inflammatory pain. The efficacy and the adverse effects of those mixtures should be explored further in clinical settings.