Pharmacological interaction between oxcarbazepine and two COX inhibitors in a rat model of inflammatory hyperalgesia

Comparative study of the effects of ibuprofen, acetaminophen, and codeine in a model of orofacial postoperative pain in male and female rats

Pain management is a primary goal after oral surgeries, but little is known about sex differences in the sensitivity to analgesics. This study aimed to compare the efficacy of three drugs with analgesic potential on heat and mechanical hyperalgesia, spontaneous pain and locomotion on male and female rats subjected to a model of orofacial postoperative pain. Male and female Wistar rats were submitted to intraoral incision or sham surgery, and on postoperative day 3, the effect of the ibuprofen (30 and 100 mg/kg), acetaminophen (100 and 300 mg/kg) and codeine (3 and 10 mg/kg) was assessed on responses to heat and mechanical facial stimulation, facial grooming, and locomotion. Ibuprofen reduced heat and mechanical hyperalgesia and grooming behavior in male and female rats in a non-sedative dose; acetaminophen dose-dependently reduced the mechanical hyperalgesia and abolished the heat hyperalgesia and the grooming behavior but caused sedation in both sexes; codeine dose-dependently reduced the mechanical hyperalgesia in male and female rats, and reduced the heat hyperalgesia, but females were less sensitive than males. It reduced spontaneous facial grooming in both sexes, but induced hyperlocomotion in females. Ibuprofen presented the most favorable profile, since it reduced over 50% heat and mechanical hyperalgesia in male and female rats, and significantly reduced spontaneous pain, without causing sedation or affecting locomotion. The identification of sex differences in the sensitivity and safety profile of frequently used analgesics can help guide the choice of more effective individualized therapies for pain control.

Combination Drug Therapy for the Management of Chronic Neuropathic Pain

Chronic neuropathic pain (NP) is an increasingly prevalent disease and leading cause of disability which is challenging to treat. Several distinct classes of drugs are currently used for the treatment of chronic NP, but each drug targets only narrow components of the underlying pathophysiological mechanisms, bears limited efficacy, and comes with dose-limiting side effects. Multimodal therapies have been increasingly proposed as potential therapeutic approaches to target the multiple mechanisms underlying nociceptive transmission and modulation. However, while preclinical studies with combination therapies showed promise to improve efficacy over monotherapy, clinical trial data on their efficacy in specific populations are lacking and increased risk for adverse effects should be carefully considered. Drug-drug co-crystallization has emerged as an innovative pharmacological approach which can combine two or more different active pharmaceutical ingredients in a single crystal, optimizing pharmacokinetic and physicochemical characteristics of the native molecules, thus potentially capitalizing on the synergistic efficacy between classes of drugs while simplifying adherence and minimizing the risk of side effects by reducing the doses. In this work, we review the current pharmacological options for the treatment of chronic NP, focusing on combination therapies and their ongoing developing programs and highlighting the potential of co-crystals as novel approaches to chronic NP management.

Eslicarbazepine acetate interacts in a beneficial manner with standard and alternative analgesics to reduce trigeminal nociception

RATIONALE

Acute pain states in the trigeminal region (headaches, dental pain) fall into the most prevalent painful conditions. Standard analgesics (paracetamol/NSAIDs) represent the cornerstone of their treatment, whereas triptans are primarily used in migraine attacks. Due to limited efficacy and/or side effects of current treatments, identifying favorable combinations of available drugs is justified.

OBJECTIVES

Eslicarbazepine acetate (ESL) is a novel antiepileptic drug whose effectiveness against trigeminal pain was recently demonstrated. Here, we examined the interactions between ESL and several standard/alternative analgesics (paracetamol, propyphenazone, naproxen, zolmitriptan, and metoclopramide) in a model of trigeminal pain.

METHODS

The antinociceptive effects of orally administered ESL, standard/alternative analgesics, and two-drug ESL-analgesic combinations were examined in the orofacial formalin test in mice. The type of interaction between drugs was determined by isobolographic analysis.

RESULTS

ESL, analgesics, and two-drug ESL-analgesic combinations significantly and dose-dependently reduced nociceptive behaviour in the second, inflammatory phase of the test. Isobolographic analysis revealed that ESL interacted additively with paracetamol/propyphenazone/zolmitriptan and synergistically with naproxen/metoclopramide (with about a 4-fold and 3-fold reduction of doses in the ESL-naproxen and ESL-metoclopramide combination, respectively).

CONCLUSIONS

ESL interacted in a beneficial manner with several analgesics that are used for trigeminal pain treatment, producing synergistic interactions with naproxen/metoclopramide and additive interactions with paracetamol/propyphenazone/zolmitriptan. Our results suggest that combining ESL with analgesics could theoretically enable the use of lower doses of individual drugs for achieving pain relief.

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.

Carbamazepine attenuates inducible nitric oxide synthase expression through Akt inhibition in activated microglial cells

Abstract Background: Carbamazepine, which was developed primarily for the treatment of epilepsy, is now also useful for the treatment of non-epileptic disorders and inflammatory hyperalgesia. However, the mechanism of its anti-neuroinflammatory action remains poorly understood.

OBJECTIVE

This study elucidates the anti-neuroinflammatory capacity of carbamazepine on microglial activation and the relative mechanisms involved.

MATERIALS AND METHODS

The microglial BV-2 cells were pretreated with carbamazepine for 15 min before activation by lipopolysaccharide (LPS). After LPS stimulation, the expression of inducible nitric oxide synthase (iNOS) was analyzed by Western blotting (WB) and reverse transcription-polymerase chain reaction. Signaling proteins and cyclooxygenase (COX)-2 were also evaluated by WB. The levels of nitrate and tumor necrosis factor (TNF)-α were analyzed by the Griess method and enzyme-linked immunosorbant assay, respectively. The formation of intracellular reactive oxygen species (ROS) was examined by fluorescent analysis.

RESULTS

Carbamazepine strongly attenuated LPS-induced production of NO and iNOS protein at concentrations of 5, 10, and 20 μM. Consistently, it could markedly suppress iNOS mRNA expression stimulated by LPS. Among the signaling pathways, LPS-mediated IκBα degradation or JNK MAPK phosphorylation was not affected by carbamazepine. Interestingly, it was found that carbamazepine could concentration-dependently inhibit LPS-activated phospho-Akt expression. Nevertheless, LPS-induced ROS production was not affected by carbamazepine. Carbamazepine (20 μM) affected either COX-2 expression or TNF-α production induced by LPS with approximately 70% and 51% inhibition, respectively.

DISCUSSION AND CONCLUSION

Our findings showed that carbamazepine exerted selective inhibition on LPS-induced microglial iNOS expression through the down-regulation of Akt activation, and thus may play a pivotal role of anti-neuroinflammation in its therapeutic efficacy.

Antihyperalgesic/Antinociceptive Effects of Ceftriaxone and Its Synergistic Interactions with Different Analgesics in Inflammatory Pain in Rodents

Background:

The β-lactam antibiotic ceftriaxone stimulates glutamate transporter GLT-1 expression and is effective in neuropathic and visceral pain models. This study examined the effects of ceftriaxone and its interactions with different analgesics (ibuprofen, celecoxib, paracetamol, and levetiracetam) in somatic and visceral pain models in rodents.

Methods:

The effects of ceftriaxone (intraperitoneally/intraplantarly), analgesics (orally), and their combinations were examined in the carrageenan-induced paw inflammatory hyperalgesia model in rats (n = 6–12) and in the acetic acid-induced writhing test in mice (n = 6–10). The type of interaction between ceftriaxone and analgesics was determined by isobolographic analysis.

Results:

Pretreatment with intraperitoneally administered ceftriaxone (10–200 mg/kg per day) for 7 days produced a significant dose-dependent antihyperalgesia in the somatic inflammatory model. Acute administration of ceftriaxone, via either intraperitoneal (10–200 mg/kg) or intraplantar (0.05–0.2 mg per paw) routes, produced a significant and dose-dependent but less efficacious antihyperalgesia. In the visceral pain model, significant dose-dependent antinociception of ceftriaxone (25–200 mg/kg per day) was observed only after the 7-day pretreatment. Isobolographic analysis in the inflammatory hyperalgesia model revealed approximately 10-fold reduction of doses of both drugs in all examined combinations. In the visceral nociception model, more than 7- and 17-fold reduction of doses of both drugs was observed in combinations of ceftriaxone with ibuprofen/paracetamol and celecoxib/levetiracetam, respectively.

Conclusions:

Ceftriaxone exerts antihyperalgesia/antinociception in both somatic and visceral inflammatory pain. Its efficacy is higher after a 7-day pretreatment than after acute administration. The two-drug combinations of ceftriaxone and the nonsteroidal analgesics/levetiracetam have synergistic interactions in both pain models. These results suggest that ceftriaxone, particularly in combinations with ibuprofen, celecoxib, paracetamol, or levetiracetam, may provide useful approach to the clinical treatment of inflammation-related pain.

Effects of oxcarbazepine on monoamines content in hippocampus and head and body shakes and sleep patterns in kainic acid-treated rats

The aim of this work was to analyze the effect of oxcarbazepine (OXC) on sleep patterns, "head and body shakes" and monoamine neurotransmitters level in a model of kainic-induced seizures. Adult Wistar rats were administered kainic acid (KA), OXC or OXC + KA. A polysomnographic study showed that KA induced animals to stay awake for the whole initial 10 h. OXC administration 30 min prior to KA diminished the effect of KA on the sleep parameters. As a measure of the effects of the drug treatments on behavior, head and body shakes were visually recorded for 4 h after administration of KA, OXC + KA or saline. The presence of OXC diminished the shakes frequency. 4 h after drug application, the hippocampus was dissected out, and the content of monoamines was analyzed. The presence of OXC still more increased serotonin, 5-hidroxyindole acetic acid, dopamine, and homovanilic acid, induced by KA.

An update on analgesics

Recent introduction of new analgesics into the clinic is best described as a slow process with activity classified into two main areas: improving analgesic efficacy/potency and reducing side-effect profile. This review article describes some of the recent advances with an emphasis on use in the acute setting. In this respect, opioids continue to be the mainstay (but not the only) analgesic and there have been important improvements in their clinical effect profile. For example, tapentadol has been introduced as a mixed opioid and norepinephrine uptake inhibitor which, unlike tramadol, does not require metabolic activation and does not suffer from isomer-dependent pharmacodynamics. Opioid antagonists have received much attention recently either used alone, methylnaltrexone (s.c) or alvimopan (p.o), or in combination, Targinact (oxycodone/naloxone), and appear to be effective in reducing opioid side-effects such as those in the gastrointestinal tract. Other agents where there has been recent development include the use of gabapentin, methylxanthines, and local anaesthetics. An interesting area of translation of basic research is in the inhibition of breakdown of endogenous opioids with opiorphin, targeting of the endocannabinoid system, and the use of ampakines to obtund opioid-induced side-effects. It is clear that there is still much work to be done, but the need for highly efficacious analgesics with good side-effect profile remains.