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.

Pregabalin can interact synergistically with Kv7 channel openers to exert antinociception in mice.

Chronic pain is a common public health problem and remains an unmet medical need. Currently available analgesics usually have limited efficacy for the treatment of chronic pain, including neuropathic pain and persistent inflammatory pain, or they are accompanied by many adverse side effects. The voltage-gated calcium channel blocker (pregabalin) and potassium channel openers (flupirtine and retigabine) have been widely used for the management of chronic pain, but their effectiveness in combination is unclear. In this research, we evaluated the antinociceptive effects of pregabalin in combination with flupirtine or retigabine in carrageenan-induced inflammatory pain and paclitaxel-induced peripheral neuropathy in mice using the von Frey test. Isobolographic analysis indicated that pregabalin exerted synergistic antinociceptive effects when combined with flupirtine or retigabine in neuropathic and inflammatory pain models. Furthermore, the antinociceptive effects of pregabalin, flupirtine/retigabine, and their combinations were significantly attenuated by the Kv7 channel blocker XE991. The favored dose ratio between pregabalin and flupirtine/retigabine in combinations was also investigated. Finally, we evaluated the motor coordination of their combinations using the rotarod test, and the outcomes underpinned their safety. Collectively, our results support the potential use of pregabalin in combination with flupirtine or retigabine to alleviate chronic pain.

Top 100 cited articles in ophthalmic epidemiology between 2006 and 2016.

AIM: To identify the most-cited articles in ophthalmic epidemiology over the last decade. METHODS: We performed a cited reference search on articles that were included in the ISI Web of Science database using the terms "Epidemi*" AND "ophthalm*" AND "population*" during year 2006 to 2016. TOP 100 most cited articles (T100) in ophthalmic epidemiology were short listed and analysed using bibliometrics. RESULTS: These top 100 articles in ophthalmic epidemiology were cited between 61 to 333 times. Of these T100 articles, 36% originated from United States, and 34% were published in the Ophthalmology journal. The three major topics identified were age-related macular degeneration (AMD, n=23), glaucoma (n=16) and visual impairment (n=12). The top-cited article was a study on outdoor activities and its association with the prevalence of myopia in school-aged children, published in 2008. CONCLUSION: This bibliometric analysis provides useful insights into the current development in ophthalmic epidemiology in the past decade and can help recognizing the quality of the researches, discoveries, and trends steering ophthalmic epidemiology.

[The structure-activity relationships of novel α7 nicotinic acetylcholine receptor agonists based on indolizine scaffold].

Alpha7 nicotinic acetylcholine receptor（α7 nAChR） is a ligand-gated ion channel critical for cognition, learning and memory. Deficiency of neuronal α7 nAChR has been implicated in the cognitive deficits and neuropsychiatric disorders. Chemical activation of α7 nAChR improves neurological functions in animal models. In this study, we designed and synthesized a series of indolizine derivatives with various substitutions at different positions on the scaffold, and investigated their structure-activity relationships（SAR）. All compounds were screened and evaluated for their agonist activity using the two-electrode voltage clamp recording system in Xenopus oocytes expressing human α7 nAChR. Compound 16 c carrying 6-methylindolizine moiety activates α7 nAChR with EC50 at 1.60 ± 0.19 µmol·L-1 and maximum effect (Emax) of 69.0% ± 2.8% compared with 3 mmol·L-1 ACh. Compound 17 b with 8-cyclopropyl substitution shows an increased Emax of 81.1% ± 9.3% with EC50 at 2.74 ± 0.74 µmol·L-1. The SAR of the series shows that introducing the small hydrophobic groups at 6- or 8- position can improve both potency and maximum effect.

[Synthesis and analgesic activities of phenyl piperazinyl aralkyl ketone derivatives].

To explore novel non-opioid analgesic agents, 16 compounds were synthesized and their structures were confirmed by 1H NMR and HR-MS. YX0611-1 was treated as the leading compound. The results of mice writhing model and hot plate model showed that compounds 2, 7, 8, 9, 11 and 15 had obvious analgesic activities in vivo. The test of affinity to mu, delta, kappa receptor displayed that active compounds didn't act on opioid receptor. The results of preliminary toxicity and pharmacokinetic tests showed that compound 7 had better safety and pharmacokinetic properties than that of YX0611-1, and it deserved further development.

[Design, synthesis and antalgic activities of aralkyl-ketone-4-piperidol derivatives].

A series of aralkyl-ketone-4-piperidol derivatives were synthesized and tested for their analgesic activities. All of the novel 30 compounds were prepared from 4-piperidone and alpha-halo-aralkyl-ketone through five steps, including Boc protection, nucleophilic addition in presence of CeCl3/NaI catalyst, deprotection, condensation and salification. Their structures were confirmed by 1H NMR and HRMS. Preliminary in vivo pharmacological trials showed that most of the synthesized compounds revealed analgesic effects. Among the tested compounds, 8, 13 and 22 exhibited potent analgesic activities in both mice writhing and mice hot plate model. The three compounds have low affinity for mu, delta, kappa receptors, which is a chance to find a better precursor of non-opioid analgesic for further optimization.