Low doses of tizanidine synergize the anti-nociceptive and anti-inflammatory effects of ketorolac or naproxen while reducing of side effects

The synergistic anti-nociceptive effects of nefopam and gabapentinoids in inflammatory, osteoarthritis, and neuropathic pain mouse models

Pain is a common public health problem and remains as an unmet medical need. Currently available analgesics usually have limited efficacy or are accompanied by many adverse side effects. To achieve satisfactory pain relief by multimodal analgesia, new combinations of nefopam and gabapentinoids (pregabalin/gabapentin) were designed and assessed in inflammatory, osteoarthritis and neuropathic pain. Isobolographic analysis was performed to analyze the interactions between nefopam and gabapentinoids in carrageenan-induced inflammatory pain, mono-iodoacetate-induced osteoarthritis pain and paclitaxel-induced peripheral neuropathic pain in mice. The anti-inflammatory effect and motor performance of monotherapy or their combinations were evaluated in the carrageenan-induced inflammatory responses and rotarod test, respectively. Nefopam (1, 3, 5, 10, 30 mg/kg, p.o.), pregabalin (3, 6, 12, 24 mg/kg, p.o.) or gabapentin (25, 50, 75, 100 mg/kg, p.o.) dose-dependently reversed mechanical allodynia in three pain models. Isobolographic analysis indicated that the combinations of nefopam and gabapentinoids exerted synergistic anti-nociceptive effects in inflammatory, osteoarthritis, and neuropathic pain mouse models, as evidenced by the experimental ED50 (median effective dose) falling below the predicted additive line. Moreover, the combination of nefopam-pregabalin/gabapentin alleviated carrageenan-induced inflammation and edema, and also prevented gabapentinoids-related sedation or ataxia by lowering their effective doses. Collectively, the co-administration of nefopam and gabapentinoids showed synergistic analgesic effects and may result in improved therapeutic benefits for treating pain.

Novel drug-drug salt crystals of metformin with ibuprofen or naproxen: Improved solubility, dissolution rate, and synergistic antinociceptive effects

As the monotherapy of available analgesics is usually accompanied by serious side effects or limited efficacy in the management of chronic pain, multimodal analgesia is widely used to achieve improved benefit-to-risk ratios in clinic. Drug-drug salts are extensively researched to optimize the physicochemical properties of active pharmaceutical ingredients (APIs) and achieve clinical benefits compared with individual APIs or their combination. New drug-drug salt crystals metformin-ibuprofen (MET-IBU) and metformin-naproxen (MET-NAP) were prepared from metformin (MET) and two poorly water-soluble anti-inflammatory drugs (IBU and NAP) by the solvent evaporation method. The structures of these crystals were confirmed by single crystal and powder X-ray diffraction, Hirshfeld surface, Fourier transform infrared spectroscopy and thermal analysis. Both MET-IBU and MET-NAP showed significantly improved solubility and intrinsic dissolution rate than the pure IBU or NAP. The stability test indicated that MET-IBU and MET-NAP have excellent physical stability under stressing test (10 days) and accelerated conditions (3 months). Moreover, isobolographic analysis suggested that MET-IBU and MET-NAP exerted potent and synergistic antinociceptive effects in λ-Carrageenan-induced inflammatory pain in mice, and both of them had an advantage in rapid pain relief. These results demonstrated the potential of MET-IBU and MET-NAP to achieve synergistic antinociceptive effects by developing drug-drug salt crystals.

Tizanidine: Advances in Pharmacology & Therapeutics and Drug Formulations

Background

Skeletal muscle relaxants (SMRs) are widely used in treating musculoskeletal conditions. All SMRs, with the exception of baclofen and tizanidine, are on the list of 2023 American Geriatrics Society Beers Criteria® for potentially inappropriate medication use in older adults. In our geriatric practice, off-label use of tizanidine as preemptive analgesia drove us to find recent advances in its pharmacology and therapeutics. An update review of tizanidine was thus presented, aiming to bring the latest knowledge to clinicians and promote further research and practical exploration.

Methods

Relevant literature up to December 2023 was identified through searches of PubMed, Web of Science, and Embase.

Results

Tizanidine, a centrally acting alpha-2 adrenoceptor agonist with both antispastic and antispasmodic activity, shows efficacy in the common indications for all SMRs. From the perspective of drug safety, tizanidine has lower incidences of adverse events (injury, delirium, encephalopathy, falls, and opioid overdose) compared to baclofen, no association with risk of Alzheimer's disease as with orphenadrine, no risk of serotonin syndrome like metaxalone when comedicated with serotonergic drugs, no significant pharmacokinetic changes in CYP2C19 poor metabolizers unlike diazepam and carisoprodol, and no physically addictive or abuse properties like carisoprodol and diazepam. From the perspective of new and potential therapeutic uses, tizanidine has additional benefits (eg, gastroprotection that can improve patient tolerance to nonsteroidal anti-inflammatory agents, anti-neuropathic pain, a key component of multimodal analgesia strategy to reduce early postoperative pain, and anti-tumor effects). New delivery systems of tizanidine are developing to improve the pharmacokinetics of oral products, including buccal patches, transdermal delivery systems, nasal spray, and in situ rectal gel.

Conclusion

Tizanidine is an SMR with unique features and may be an optimal initial choice for older adults. There would be more scientific studies, wider therapeutic applications, and new drug formulations in the future.

Sex-dependent antiallodynic effect of α2 adrenergic receptor agonist tizanidine in rats with experimental neuropathic pain

The purpose of this study was to investigate the mechanism of antiallodynic effect of tizanidine in neuropathic rats. Spinal nerve ligation reduced withdrawal threshold which was interpreted as tactile allodynia. Increasing doses of tizanidine induced a dose-dependent antiallodynic effect in nerve injured rats. Tizanidine was more effective in female than male neuropathic rats. This drug induced a lower antiallodynic effect in ovariectomized, compared with non-ovariectomized, neuropathic rats, while systemic reconstitution of estradiol (E2) levels in ovariectomized neuropathic females fully restored the antiallodynic effect of tizanidine. Naloxone reduced the antiallodynic effect of tizanidine in male but not in female neuropathic rats. Ovariectomy restored the antagonizing effect of naloxone in the antiallodynic effect of tizanidine, whereas treatment with E2 abolished the effect of naloxone on tizanidine activity. Rauwolscine (α₂ antagonist) and imiloxan (α_2B antagonist) completely abated tizanidine-induced antiallodynic effect in female neuropathic rats. In contrast, BRL-44408 (α_2A antagonist) partially decreased the effect of tizanidine while JP-1302 (α_2C antagonist) was ineffective. Rauwolscine, imiloxan and BRL-44408 decreased withdrawal threshold in naïve female rats. Rauwolscine did not modify withdrawal threshold in naïve male rats. AGN192403 (I₁ antagonist), BU224 (I₂ antagonist), prazosin (α₁ antagonist) and methiothepin (5-HT antagonist) did not modify tizanidine-induced antiallodynia in neuropathic females and males. These data indicate that tizanidine exhibits a sex-dependent antiallodynic effect in neuropathy. Data also suggest that activation of adrenergic α_2B and α_2A and opioid receptors participate in the antiallodynic effect of tizanidine in female and male, respectively, neuropathic rats.

Isobolographic analysis of antinociceptive effect of ketorolac, indomethacin, and paracetamol after simultaneous peripheral local and systemic administration

This study was designed to characterize the type of interaction (subadditive, additive, or synergistic) after simultaneous administration by two different routes (intraperitoneal plus peripheral local) of the same nonsteroidal anti-inflammatory drugs (NSAID) ketorolac and indomethacin or paracetamol. The antinociceptive effects of locally or intraperitoneally delivery of NSAIDs or paracetamol, and the simultaneous administration by the two routes at fixed-dose ratio combination were evaluated using the formalin test. Pain-related behavior was quantified as the number of flinches of the injected paw. Isobolographic analysis was used to characterize the interaction between the two routes. ED30 values were estimated for individual drugs, and isobolograms were constructed. Ketorolac, indomethacin, or paracetamol and fixed-dose ratio combinations produced a dose-dependent antinociceptive effect in the second but not in the first phase of the formalin test. The analysis of interaction type after simultaneous administration by the two routes the same NSAID or paracetamol (on basis of their ED30), revealed that the simultaneous administration of ketorolac or paracetamol was additive and for indomethacin was synergistic. Since the mechanisms underlying the additive effect of ketorolac or paracetamol and the synergistic effect of indomethacin were not explored; it is possible that the peripheral and central mechanism is occurring at several anatomical sites. The significance of these findings for theory and pain pharmacotherapy practice indicates that the combination of one analgesic drug given simultaneously by two different administration routes could be an additive or it could lead to a synergistic interaction.

An Experimental Comparison of the Analgesic and Anti-Inflammatory Effects of Safflower Oil, Benzydamine HCl, and Naproxen Sodium

The study aims to establish how feasible a natural therapy option (safflower oil) is in the treatment of postoperative pain. Naproxen sodium has already been experimentally proven to be effective for this purpose. Accordingly, the analgesic and anti-inflammatory effects of safflower oil were compared with those obtained with benzydamine HCl and naproxen sodium. Forty-two, healthy, adult female rats of Wistar albino species were divided at random into six groups of seven rats. The intervention allocation was as follows: Group No. 1-physiological saline 0.9%; Group No. 2-safflower oil 100 mg/kg; Group No. 3-safflower oil 300 mg/kg; Group No. 4-benzydamine HCl 30 mg/kg; Group No. 5-benzydamine HCl 100 mg/kg; and Group No. 6-naproxen sodium 10 mg/kg. Following allocation of treatment, pain was induced experimentally and tested in various ways (hot plate test, tail-pinching test, and writhing test) and the efficacy of each treatment in providing peripheral and central analgesia was evaluated. The second stage consisted of providing different treatments to four groups (groups 7-10) of seven rats each, chosen at random. The allocations were as follows: Group No. 7-physiological saline 0.9%; Group No. 8-safflower oil 300 mg/kg; Group No. 9-benzydamine HCl 100 mg/kg; and Group No. 10-naproxen sodium 10 mg/kg. To create experimental inflammation, 2% formaldehyde was injected into the experimental animal's paw and the resulting edema was measured and recorded for a 10-day period. Edema inhibition was calculated as a percentage. The rats were sacrificed and the paw and stomach dissected for histopathological examination. The data were used for statistical analysis, using the Shapiro-Wilk, Kruskal-Wallis H test, and two-way analysis of variance. In the tail-pinching test, it was determined that a 300 mg/kg dose of safflower oil shows central spinal analgesic efficacy and this effect is close in magnitude to 10 mg/kg of the reference material, naproxen sodium. In the squirming test, it was observed that the 100 and 300 mg/kg doses of safflower oil had a peripheral analgesic effect when compared with the serum physiological (placebo) group. The peripheral efficacy of 300 mg/kg safflower oil was found to approximate that of 10 mg/kg naproxen sodium. In rats treated with benzydamine HCl 100 mg/kg, similar peripheral analgesic efficacy to naproxen sodium 10 mg/kg was noted. In the hot plate test, no difference in the analgesic efficacy between the various agents was found. The change in inhibition of edema between the 1st and 10th days was most marked in rats receiving naproxen sodium 10 mg/kg. A significant difference was determined in the safflower oil 300 mg/kg and benzydamine HCl 100 mg/kg groups (P < .001). Regarding histopathology findings in the rat paw, significant differences were seen in venous congestion between placebo and safflower oil 300 mg/kg and in inflammation between the control and benzydamine HCl 100 mg/kg groups. Regarding the histopathology findings in the rat stomach, significant differences were observed in venous congestion between placebo and safflower oil 300 mg/kg; in damage to the epithelium between placebo and safflower oil 300 mg/kg and between naproxen sodium 10 mg/kg and safflower oil; and in cell infiltration and development of edema between placebo and safflower oil 300 mg/kg. It is predicted that further research into safflower oil and benzydamine HCl will create opportunities to develop analgesic-anti-inflammatory therapeutics of a novel kind for the treatment of postoperative pain and inflammation.

Stimulation of Erythrocyte Membrane Blebbing by Naproxen Sodium

Naproxen sodium is a nonsteroidal anti-inflammatory drug (NSAID) having antipyretic and analgesic properties, mainly used for the treatment of rheumatoid arthritis and osteoarthritis. Eryptosis is an alternative term used for suicidal erythrocyte death. In the current study, eryptotic effect of naproxen sodium characterized by membrane blebbing was investigated in erythrocytes after 48 hours of treatment with different concentrations (1-25 µM). The experimental work related to investigation of eryptosis was done by cell size measurement and confirmation of calcium role in the induction of membrane blebbing. As a possible mechanism of eryptosis, oxidative stress induced by naproxen sodium was determined by catalase, glutathione peroxidase, and superoxide dismutase activities. Similarly, hemolytic effect of naproxen sodium was also determined by hemolysis measurement. Results of our study illustrated that the therapeutic doses (10-25 µM) of naproxen sodium induce oxidative stress, confirmed by significant decrease in superoxide dismutase, catalase, and glutathione peroxidase activities that lead to the triggering of cell death by eryptosis and hemolysis.

Structure-based design of 2,4-diaminopyrimidine derivatives bearing a pyrrolyl group as ALK and ROS1 inhibitors

Twenty-eight 2,4-diaminopyrimidine derivatives (9a–9n and 10a–10n) bearing a pyrrolyl moiety were designed and synthesized based on the co-crystal structure of ceritinib with ALK^wt protein and compound 10d bearing sulfonamide (R¹) and 4-methylpiperazinyl (R²) moiety was of great promising.

A dual amylin and calcitonin receptor agonist inhibits pain behavior and reduces cartilage pathology in an osteoarthritis rat model

OBJECTIVES

Pain and disability are the main clinical manifestations of osteoarthritis, for which only symptomatic therapies are available. Hence, there is a need for therapies that can simultaneously alter disease progression and provide pain relief. KBP is a dual amylin- and calcitonin-receptor agonist with antiresorptive and chondroprotective properties. In this study we investigated the effect of KBP in a rat model of osteoarthritis.

METHODS

Medial meniscectomy (MNX) was performed in 39 rats, while 10 underwent sham surgery. Rats were treated with KBP and/or naproxen. Nociception was assessed by mechanical and cold allodynia, weight bearing asymmetry, and burrowing behavior. Blood samples were collected for biomarker measurements, and knees for histology. Cartilage histopathology was evaluated according to the advanced Osteoarthritis Research International (OARSI) score and KBPs in vitro antiresorptive effects were assessed using human osteoclasts cultured on bone.

RESULTS

The MNX animals displayed an increased nociceptive behavior. Treatment with KBP attenuated the MNX-induced osteoarthritis-associated joint pain. The cartilage histopathology was significantly lower in rats treated with KBP than in MNX animals. Bone and cartilage degradation, assessed by CTX-I and CTX-II plasma levels, were decreased in all KBP-treated groups and KBP potently inhibited bone resorption in vitro.

CONCLUSIONS

Our study demonstrates the effectiveness of KBP in ameliorating osteoarthritis-associated joint pain and in protecting the articular cartilage, suggesting KBP as a potential drug candidate for osteoarthritis.

Synthesis and antinociceptive evaluation of bioisosteres and hybrids of naproxen, ibuprofen and paracetamol

The aim of this work was to design, synthesize and characterize the potential anti-nociceptive and anti-inflammatory activities of a new series of bioisosteres and hybrids from known non-steroidal anti-inflammatory drugs (NSAIDs). The compounds 4-(acetylamino)phenyl (2S)-2-(6-methoxy-2-naphthyl)propanoate (GUF-1) and 4-(acetylamino)phenyl 2-(R,S)-(4-isobutylphenyl)propanoate (GUF-2) were synthesized as hybrids (also known as heterodimers); whereas those named 2-(R,S)-(4-isobutylphenyl)-N-1H-tetrazol-5-ylpropanamide (GUF-3), (2S)-2-(6-methoxy-2-naphthyl)-N-1H-tetrazol-5-ylpropanamide (GUF-4), [2-(R,S)-N-hydroxy-2-[4-(2-methylpropyl)phenyl]propanamide] (GUF-5), and (2S)-N-hydroxy-2-(6-methoxy-2-naphthyl)propanamide (GUF-6) were synthesized as bioisosteres of the NSAIDs paracetamol, ibuprofen, and naproxen, respectively. All these compounds were characterized by spectroscopic and spectrometric analysis. Antinociceptive activity of GUF-1 to GUF-6 was evaluated using the formalin test in rats. Pharmacological responses of GUF-1, GUF-2 (hybrids), and GUF-5 (bioisostere) demonstrated significant antinociceptive effects; thus these compounds were assayed in an inflammation test like carrageenan-induced paw oedema in rats. Complete molecular docking of cyclooxygenase and the GUF-1 and GUF-2 hybrids showed high docking scores, compared to the reference drugs. Our data demonstrate that compounds GUF-1, GUF-2, and GUF-5 possesses antinociceptive and antiinflammatory activities resembling and improving those known for the traditional NSAIDs, paracetamol, naproxen and ibuprofen.