Effects of fadolmidine, an α2 -adrenoceptor agonist, as an adjuvant to spinal bupivacaine on antinociception and motor function in rats and dogs

α2 -Adrenoceptor agonists such as clonidine and dexmedetomidine are used as adjuvants to local anesthetics in regional anesthesia. Fadolmidine is an α2 -adrenoceptor agonist developed especially as a spinal analgesic. The current studies investigate the effects of intrathecally administered fadolmidine with a local anesthetic, bupivacaine, on antinociception and motor block in conscious rats and dogs. The antinociceptive effects of intrathecal fadolmidine and bupivacaine alone or in combination were tested in the rat tail-flick and the dog's skin twitch models. The durations of motor block in rats and in dogs were also assessed. In addition, the effects on sedation, mean arterial blood pressure, heart rate, respiratory rate and body temperature were evaluated in telemetrized dogs. Concentrations of fadolmidine in plasma and spinal cord were determined after intrathecal and intravenous administration in rats. Co-administration of intrathecal fadolmidine with bupivacaine increased the magnitude and duration of the antinociceptive effects and prolonged motor block without hypotension. The interaction of the antinociceptive effect was synergistic in its nature in rats. Concentration of fadolmidine in plasma was very low after intrathecal dosing. Taken together, these studies show that fadolmidine as an adjuvant to intrathecal bupivacaine provides enhanced sensory-motor block and enables a reduction of the doses of both drugs. The results indicate that co-administration of fadolmidine with intrathecal bupivacaine was able to achieve an enhanced antinociceptive effect without hypotension and could thus represent a suitable combination for spinal anesthesia.

Evaluation of the Pharmacokinetic Interaction and Safety of Atogepant Co-Administered with Acetaminophen or Naproxen in Healthy Participants: A Randomized Trial

Background

Atogepant is an oral calcitonin gene-related peptide (CGRP) receptor antagonist in development for preventive treatment of migraine.

Objective

To evaluate potential pharmacokinetic drug–drug interactions (DDIs), safety and tolerability of atogepant co-administered with acetaminophen or naproxen in healthy participants.

Methods

This open-label, randomized, five-way crossover, single-center, phase 1 DDI trial randomized healthy adult participants to one of ten intervention sequences to receive single-dose 60 mg atogepant, 1000 mg acetaminophen, 500 mg naproxen, or co-administrations of atogepant with acetaminophen or naproxen, with 7-day washout periods between interventions. Potential DDIs were assessed using geometric mean ratios and 90% confidence intervals (CIs) calculated from maximum plasma drug concentrations (C_max) and area under the plasma drug concentration-time curves (AUCs) for co-administered medications versus medications administered alone. Secondary pharmacokinetic parameters [time to C_max (t_max), terminal elimination half-life (t_1/2), volume of distribution during terminal phase (V_Z/F), total body clearance (CL/F)], and safety were evaluated.

Results

Forty participants enrolled; 35 (87.5%) completed the trial. Atogepant C_max was unchanged, AUC_0–t and AUC_0–∞ both increased 13%, and t_max and t_1/2 were unchanged when co-administered with acetaminophen; and acetaminophen C_max decreased 11%, AUC_0–t and AUC_0–∞ both decreased 6%, and t_max and t_1/2 were unchanged when co-administered with atogepant. Atogepant mean (SD) V_z/F and CL/F were 369.45 (255.68) L and 18.88 (9.28) L/h, respectively, when administered alone and 297.56 (196.01) L and 16.33 (6.11) L/h when co-administered with acetaminophen. Atogepant C_max was unchanged, AUC_0–t and AUC_0–∞ both decreased 1%, and t_max and t_1/2 were unchanged when co-administered with naproxen; and naproxen C_max decreased 6%, AUC_0–t and AUC_0–∞ both decreased 2%, and t_max and t_1/2 were unchanged when co-administered with atogepant. Atogepant mean (SD) V_z/F and CL/F were 359.61 (247.99) L and 18.80 (7.78) L/h, respectively, when co-administered with naproxen. Treatment-emergent adverse events (TEAEs) occurred at rates of 5.6–21.1% across interventions. The most commonly reported TEAEs were oropharyngeal pain (n = 2, with atogepant; not treatment related) and nausea (n = 2, with atogepant/acetaminophen; treatment related).

Conclusion

Co-administration of 60 mg atogepant with 1000 mg acetaminophen or 500 mg naproxen was safe and well tolerated in healthy participants, and no DDIs were observed.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40261-021-01034-5.

Antinociceptive effects of rotigotine-loaded microspheres and its synergistic interactions with analgesics in inflammatory pain in rats

Rotigotine-loaded microspheres (RoMS) are sustained-release formulations with prolonged anti-Parkinson's effects. Given that pain is a non-motor symptom of Parkinson's disease, this study investigated the antinociceptive effects of RoMS and their synergistic effects with analgesics on inflammatory pain. A model of inflammatory pain was prepared by intraplantarly injecting male Sprague-Dawley rats with carrageenan. The antinociceptive effects of RoMS, acetaminophen, and tramadol, both alone and in combination, were evaluated using the hind paw withdrawal latency in the hot plate test and Randall-Selitto test. The rotigotine concentrations in serum and tissues were assayed using ultra-performance liquid chromatography-tandem mass spectrometry. Isobolographic analysis was performed to evaluate the nature of the interactions of RoMS with acetaminophen or tramadol. The results showed that hind paw withdrawal latency to thermal and mechanical stimuli was significantly increased on day 3 and 7 after administered RoMS. Rotigotine could be detected in serum and tissues 3 and 7 days after an intramuscular injection of RoMS. However, the rotigotine concentration fell the detection limit of the assay on day 14 after administration. RoMS produced synergistic antinociceptive effects in the inflammatory pain model when RoMS is combined with acetaminophen or tramadol. These findings suggest that RoMS can relieve inflammatory pain in rats. Furthermore, the combination of RoMS with acetaminophen or tramadol produces synergistic antinociception, which may be clinically worthy because combination therapies may reduce the drug doses required for antinociception.

A Personalized Medicine Approach Using Clinical Utility Index and Exposure-Response Modeling Informed by Patient Preferences Data

Selection of a personalized dose for an individual patient can be informed by the patient's preferences, translated as weights on each of the clinically relevant safety and efficacy drug attributes, based on results from a brief patient preference elicitation questionnaire. In this analysis, the weighted attributes were simulated to represent various endometriosis patient profiles. Exposure-response simulations were performed for elagolix, a drug approved for management of moderate to severe pain associated with endometriosis, across a range of plasma exposures corresponding to a range of doses. The results were combined to calculate a personalized clinical utility index. An interactive user-friendly online application was developed and envisioned as a physician's desk tool to personalize the dose selection process based on individual patient preferences. This demonstration should serve as an example of how patient/physician conversation can be facilitated with quantitative tools for personalizing the dose.

EST64454: a Highly Soluble σ1 Receptor Antagonist Clinical Candidate for Pain Management

The synthesis and pharmacological activity of a new series of pyrazoles that led to the identification of 1-(4-(2-((1-(3,4-difluorophenyl)-1H-pyrazol-3-yl)methoxy)ethyl)piperazin-1-yl)ethanone (9k, EST64454) as a σ1 receptor (σ1R) antagonist clinical candidate for the treatment of pain are reported. The compound 9k is easily obtained through a five-step synthesis suitable for the production scale and shows an outstanding aqueous solubility, which together with its high permeability in Caco-2 cells will allow its classification as a BCS class I compound. It also shows high metabolic stability in all species, linked to an adequate pharmacokinetic profile in rodents, and antinociceptive properties in the capsaicin and partial sciatic nerve ligation models in mice.

Traditional uses, phytochemistry, pharmacology, pharmacokinetics and toxicology of the fruit of Tetradium ruticarpum: A review

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Tetradium ruticarpum (FTR) known as Tetradii fructus or Evodiae fructus (Wu-Zhu-Yu in Chinese) is a versatile herbal medicine which has been prescribed in Chinese herbal formulas and recognized in Japanese Kampo. FTR has been clinically used to treat various diseases such as headache, vomit, diarrhea, abdominal pain, dysmenorrhea and pelvic inflammation for thousands of years.

AIM OF THE REVIEW

The present paper aimed to provide comprehensive information on the ethnopharmacology, phytochemistry, pharmacology, pharmacokinetics, drug interaction and toxicology of FTR in order to build up a foundation on the mechanism of ethnopharmacological uses as well as to explore the trends and perspectives for further studies.

MATERIALS AND METHODS

This review collected the literatures published prior to July 2020 on the phytochemistry, pharmacology, pharmacokinetics and toxicity of FTR. All relevant information on FTR was gathered from worldwide accepted scientific search engines and databases, including Web of Science, PubMed, Elsevier, ACS, ResearchGate, Google Scholar, and Chinese National Knowledge Infrastructure (CNKI). Information was also obtained from local books, PhD. and MSc. Dissertations as well as from Pharmacopeias.

RESULTS

FTR has been used as an herbal medicine for centuries in East Asia. A total of 165 chemical compounds have been isolated so far and the main chemical compounds of FTR include alkaloids, terpenoids, flavonoids, phenolic acids, steroids, and phenylpropanoids. Crude extracts, processed products (medicinal slices) and pure components of FTR exhibit a wide range of pharmacological activities such as antitumor, anti-inflammatory, antibacterial, anti-obesity, antioxidant, insecticide, regulating central nervous system (CNS) homeostasis, cardiovascular protection. Furthermore, bioactive components isolated from FTR can induce drug interaction and hepatic injury.

CONCLUSIONS

Therapeutic potential of FTR has been demonstrated with the pharmacological effects on cancer, inflammation, cardiovascular diseases, CNS, bacterial infection and obesity. Pharmacological and pharmacokinetic studies of FTR mostly focus on its main active alkaloids. Further in-depth studies on combined medication and processing approaches mechanisms, pharmacological and toxic effects not limited to the alkaloids, and toxic components of FTR should be designed.

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.

The leaves of Bougainvillea spectabilis suppressed inflammation and nociception in vivo through the modulation of glutamatergic, cGMP, and ATP-sensitive K+ channel pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Bougainvillea spectabilis is an ornamental shrub from Nyctaginaceae family, widely used in the traditional medicine in the treatment of pain, inflammation, and ulcer. Some research investigated the analgesic potential of this plant, however, the in-depth analysis of its antinociceptive properties and molecular mechanism(s) are yet to be revealed.

PURPOSE OF THE STUDY

This study, therefore, investigated the antinociceptive potential of methanol extract of the leaves of B. spectabilis (MEBS) with possible molecular mechanism(s) of action using several pre-clinical models of acute and chronic pain in mice.

MATERIALS AND METHODS

The dry leaf powder of B. spectabilis was macerated with 100% methanol, and then dried crude extract was used for in vivo experiments. Following the acute toxicity test with 500, 1000, and 2000 mg/kg b.w. doses of MEBS, the central antinociceptive activities of the extract (50, 100, and 200 mg/kg b.w.) were evaluated using hot plate and tail immersion tests, whereas the peripheral activities were investigated using acetic acid-induced writhing, formalin-induced licking and oedema, and glutamate-induced licking tests. Moreover, the possible involvements of cGMP and ATP-sensitive K+ channel pathways in the observed antinociceptive activities were also investigated using methylene blue (20 mg/kg b.w.) and glibenclamide (10 mg/kg b.w.), respectively. We also performed GC/MS-MS analysis of MEBS to identify the phyto-constituents and in silico modelling of the major compounds for potential molecular targets.

RESULTS

Our results demonstrated that MEBS at 50, 100, and 200 mg/kg b.w. doses were not effective enough to suppress centrally mediated pain in the hot plate and tail immersion models. However, the extract was potent (at 100 and 200 mg/kg b.w. doses) in reducing peripheral nociception in the acetic acid-induced writhing and inflammatory phase of the formalin tests. Further analyses revealed that MEBS could interfere with glutamatergic system, cGMP and ATP-sensitive K⁺ channel pathways to show its antinociceptive properties. GC/MS-MS analysis revealed 35 different phytochemicals with potent anti-inflammatory and antinociceptive properties including phytol, neophytadiene, 2,4-Di-tert-butylphenol, fucoxanthin, and Vit-E. Prediction analysis showed high intestinal absorptivity and low toxicity profiles of these compounds with capability to interact with glutamatergic system, inhibit JAK/STAT pathway, scavenge nitric oxide and oxygen radicals, and inhibit expression of COX3, tumor necrosis factor, and histamine.

CONCLUSION

Taken together, these results suggested the antinociceptive potentials of MEBS which were mediated through the modulation of glutamatergic, cGMP, and ATP-sensitive K⁺ channel pathways. These also suggested that MEBS could be beneficial in the treatment of complications associated with nociceptive pain.

Pharmacokinetics of an intravenous constant rate infusion of a morphine-lidocaine-ketamine combination in Holstein calves undergoing umbilical herniorrhaphy

OBJECTIVE

To describe the pharmacokinetics of morphine, lidocaine, and ketamine associated with IV administration of a constant rate infusion (CRI) of a morphine-lidocaine-ketamine (MLK) combination to calves undergoing umbilical herniorrhaphy.

ANIMALS

20 weaned Holstein calves with umbilical hernias.

PROCEDURES

Calves were randomly assigned to receive a CRI of an MLK solution (0.11 mL/kg/h; morphine, 4.8 μg/kg/h; lidocaine, 2.1 mg/kg/h; and ketamine, 0.42 mg/kg/h) for 24 hours (MLK group) or 2 doses of flunixin meglumine (1.1 mg/kg, IV, q 24 h) and a CRI of saline (0.9% NaCl) solution (0.11 mL/kg/h) for 24 hours (control group). For all calves, the CRI was begun after anesthesia induction. Blood samples were obtained immediately before and at predetermined times for 120 hours after initiation of the assigned treatment. Noncompartmental analysis was used to estimate pharmacokinetic parameters for the MLK group.

RESULTS

During the CRI, steady-state serum concentrations were achieved for lidocaine and ketamine, but not morphine. Mean terminal half-life was 4.1, 0.98, and 1.55 hours and area under the concentration-time curve was 41, 14,494, and 7,426 h•μg/mL for morphine, lidocaine, and ketamine, respectively. After the CRI, the mean serum drug concentration at steady state was 6.3, 616.7, and 328 ng/mL for morphine, lidocaine, and ketamine, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

During the CRI of the MLK solution, steady-state serum concentrations were achieved for lidocaine and ketamine, but not morphine, likely owing to the fairly long half-life of morphine. Kinetic analyses of MLK infusions in cattle are necessary to establish optimal dosing protocols.

Pharmacokinetic Profiles of Gabapentin after Oral and Subcutaneous Administration in Black-tailed Prairie Dogs (Cynomys ludovicianus)

In veterinary and human medicine, gabapentin (a chemical analog of γ-aminobutyric acid) is commonly prescribed to treat postoperative and chronic neuropathic pain. This study explored the pharmacokinetics of oral and subcutaneous administration of gabapentin at high (80 mg/kg) and low (30 mg/kg) doses as a potential analgesic in black-tailed prairie dogs (Cynomys ludovicianus; n = 24). The doses (30 and 80 mg/kg) and half maximal effective concentration (1.4 to 16.7 ng/mL) for this study were extrapolated from pharmacokinetic efficacy studies in rats, rabbits, and cats. Gabapentin in plasma was measured by using an immunoassay, and data were evaluated using noncompartmental analysis. The peak plasma concentrations (mean ±1 SD) were 42.6 ±14.8 and 115.5 ±15.2 ng/mL, respectively, after 30 and 80 mg/kg SC and 14.5 ±3.5 and 20.7 ±6.1 ng/mL after the low and high oral dosages, respectively. All peak plasma concentrations of gabapentin occurred within 5 h of administration. Disappearance half-lives for the low and high oral doses were 7.4 ± 6.0 h and 5.0 ± 0.8 h, respectively. The results of this study demonstrate that oral administration of gabapentin at low (30 mg/kg) doses likely would achieve and maintain plasma concentrations at half maximum effective concentration for 12 h, making it a viable option for an every 12-h treatment.

Pharmacological characterization of a novel, potent, selective, and orally active fatty acid amide hydrolase inhibitor, PKM-833 [(R)-N-(pyridazin-3-yl)-4-(7-(trifluoromethyl)chroman-4-yl)piperazine-1-carboxamide] in rats: Potential for the treatment of inflammatory pain

Recently, we identified a novel fatty acid amide hydrolase (FAAH) inhibitor, PKM-833 [(R)-N-(pyridazin-3-yl)-4-(7-(trifluoromethyl)chroman-4-yl)piperazine-1-carboxamide]. The aim of the present study is to characterize the pharmacological profile of PKM-833 in vitro and in vivo. PKM-833 showed potent inhibitory activities against human and rat FAAH with IC50 values of 8.8 and 10 nmol/L, respectively, 200-fold more selectivity against other 137 molecular targets, and irreversible mode of action. In pharmacokinetic and pharmacodynamic studies, PKM-833 showed excellent brain penetration and good oral bioavailability, and elevated anandamide (AEA) concentrations in the rat brain. These data indicate that PKM-833 is a potent, selective, orally active, and brain-penetrable FAAH inhibitor. In behavioral studies using rat models, PKM-833 significantly attenuated formalin-induced pain responses (3 mg/kg) and improved mechanical allodynia in complete freund's adjuvant (CFA)-induced inflammatory pain (0.3-3 mg/kg). On the other hand, PKM-833 did not show the analgesic effects against mechanical allodynia in chronic constriction injury (CCI)-induced neuropathic pain up to 30 mg/kg. Regarding side effects, PKM-833 had no significant effects on catalepsy and motor coordination up to 30 mg/kg. These results indicate that PKM-833 is a useful pharmacological agent that can be used to investigate the role of FAAH and may have therapeutic potential for the treatment of inflammatory pain without undesirable side effects.

Preliminary in Vitro Assessment of the Potential of EST64454, a Sigma-1 Receptor Antagonist, for Pharmacokinetic Drug-Drug Interactions

EST64454 is a selective sigma-1 receptor ligand intended for orally administered pain treatment that showed a promising profile in the lead optimization process. As part of the preliminary compound profiling, the potential for future drug-drug interactions was explored in vitro. Both direct and time-dependent CYP inhibition for CYP1A2, 2C9, 2C19, 2D6 and 3A4 was studied in human liver microsomes. EST64454 showed a low potential for CYP inhibition (IC50 between 100 and 1000 µM) and as time-dependent inhibitor (IC50 shift mainly around 1). CYP induction studies with HepaRG™ cells revealed no CYP induction at concentrations ≤50 µM, as shown by the CYP1A2, 3A4 and 2B6 activities measured. Reaction phenotyping was assessed after incubation with recombinant human enzymes. Although a very low metabolism was observed, several enzymes catalyzed the formation of metabolites, including CYP3A4, 2C19 and flavin monooxygenases (FMO) 1 and 3. EST64454 was not a P-glycoprotein (P-gp) substrate and was highly permeable in Caco-2 cells. P-gp inhibition was only observed at 200 µM, the highest concentration studied. Preliminary studies suggest that neither CYP nor P-gp interaction of EST64454 would be of any concern for further development. At later stages, the interaction kinetics and the clinical relevance of these findings will be thoroughly evaluated.

Clinical Management of Pain in Rodents

The use of effective regimens for mitigating pain remain underutilized in research rodents despite the general acceptance of both the ethical imperative and regulatory requirements intended to maximize animal welfare. Factors contributing to this gap between the need for and the actual use of analgesia include lack of sufficient evidence-based data on effective regimens, under-dosing due to labor required to dose analgesics at appropriate intervals, concerns that the use of analgesics may impact study outcomes, and beliefs that rodents recover quickly from invasive procedures and as such do not need analgesics. Fundamentally, any discussion of clinical management of pain in rodents must recognize that nociceptive pathways and pain signaling mechanisms are highly conserved across mammalian species, and that central processing of pain is largely equivalent in rodents and other larger research species such as dogs, cats, or primates. Other obstacles to effective pain management in rodents have been the lack of objective, science-driven data on pain assessment, and the availability of appropriate pharmacological tools for pain mitigation. To address this deficit, we have reviewed and summarized the available publications on pain management in rats, mice and guinea pigs. Different drug classes and specific pharmacokinetic profiles, recommended dosages, and routes of administration are discussed, and updated recommendations are provided. Nonpharmacologic tools for increasing the comfort and wellbeing of research animals are also discussed. The potential adverse effects of analgesics are also reviewed. While gaps still exist in our understanding of clinical pain management in rodents, effective pharmacologic and nonpharmacologic strategies are available that can and should be used to provide analgesia while minimizing adverse effects. The key to effective clinical management of pain is thoughtful planning that incorporates study needs and veterinary guidance, knowledge of the pharmacokinetics and mechanisms of action of drugs being considered, careful attention to individual differences, and establishing an institutional culture that commits to pain management for all species as a central component of animal welfare.

Pharmacokinetics and pharmacodynamics of mitragynine, the principle alkaloid of Mitragyna speciosa: present knowledge and future directions in perspective of pain

Mitragyna speciosa, commonly known as Ketum or Biak in Malaysia and Kratom in Thailand, is a native plant to Southeast Asia and has various pharmacological benefits. Mitragynine (MG) is the principal alkaloid found in the leaves of Mitragyna speciosa and has been reported to be responsible for the plant's therapeutic actions. Traditionally, local communities use Kratom preparations for relief from different types of pain. The potential analgesic effects of MG using rodent models have been reported in literatures. We have reviewed the published analgesic and pharmacokinetic studies and all of these findings showed the routes of drug administration, doses employed, and type of vehicles used to solubilize the drug, varied considerably; hence this posted difficulties in predicting the drug's pharmacokinetic-response relationship. A rational approach is warranted for accurate prediction of dose-response relationship; as this is essential for the development of MG as an alternative medicinal drug for pain management. PKPD modeling would serve as a better method to understand the dose-response relationship in future MG preclinical and clinical studies.

Pharmacokinetic-pharmacodynamic modelling of the antinociceptive effect of a romifidine infusion in standing horses

OBJECTIVE

To evaluate the effect of a romifidine infusion on antinociception and sedation, and to investigate its relationship with plasma concentration.

STUDY DESIGN

Prospective, experimental, nonrandomized trial.

ANIMALS

A total of 10 healthy adult warmblood horses.

METHODS

Romifidine (loading dose: 0.08 mg kg^-1, infusion: 0.03 mg kg^-1 hour^-1) was administered intravenously over 120 minutes. Romifidine plasma concentrations were determined by capillary electrophoresis. Sedation quality and nociceptive thresholds were evaluated at regular time points before, during and after romifidine administration. The nociceptive withdrawal reflex was elicited by electrical stimulation at the thoracic limb using a dedicated threshold tracking algorithm and recorded by electromyography at the deltoid muscle. A pharmacokinetic-pharmacodynamic model was established and correlation between romifidine plasma concentration and main output variables tested.

RESULTS

A two compartmental model best described the romifidine pharmacokinetic profile. The nociceptive thresholds increased compared with baseline in all horses from 10 to 146 minutes after romifidine administration (p < 0.001). Peak effect reached 5.7 ± 2.3 times the baseline threshold (mean ± standard deviation). The effect/concentration relationship followed a counter-clockwise hysteresis loop. The mean plasma concentration was weakly correlated to nociceptive thresholds (p < 0.0071, r = 0.392). The sedative effects were significant until 160 minutes but variable, not correlated to plasma concentration (p = 0.067), and weakly correlated to nociceptive thresholds (p < 0.0001, r = 0.33).

CONCLUSIONS AND CLINICAL RELEVANCE

Romifidine elicited a marked antinociceptive effect. Romifidine-induced antinociception appeared with a delayed onset and lasted longer than sedation after discontinuing its administration.

Neoline is the active ingredient of processed aconite root against murine peripheral neuropathic pain model, and its pharmacokinetics in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Processed aconite root (PA), the root of Aconitum carmichaeli (Ranunculaceae), is a crude drug used in traditional Chinese or Japanese kampo medicine to treat pain associated with coldness. In our previous study, PA and its active ingredient, neoline, alleviated oxaliplatin-induced peripheral neuropathy in mice.

AIM OF THE STUDY

The present study investigated the effects of PA on a murine peripheral neuropathy model induced by intraperitoneal injection of paclitaxel and partial ligation of the sciatic nerve (Seltzer model), and identified its active ingredients.

MATERIALS AND METHODS

PA powder (1 g/kg/day) was orally administered, and either neoline or benzoylmesaconine (10 mg/kg/day) was subcutaneously injected into the murine model. Mechanical hyperalgesia was evaluated via the von Frey filament method. PA extract was orally administered to rats; blood samples were chronologically collected, and the plasma concentrations of Aconitum alkaloids were measured. The contents of Aconitum alkaloids in commercial PA products were also measured.

RESULTS

PA extract and neoline significantly attenuated the mechanical hyperalgesia induced by either paclitaxel or partial ligation of the sciatic nerve in mice. In the plasma samples of rats treated with PA extract, higher concentrations of benzoylmesaconine and neoline were apparent among Aconitum alkaloids. The contents of benzoylmesaconine and neoline varied among PA products with different processing procedures. Subcutaneous injection of benzoylmesaconine did not attenuate the hyperalgesia induced by each paclitaxel, partial ligation of the sciatic nerve, or oxaliplatin in mice.

CONCLUSIONS

The present results indicate that PA and its active ingredient, neoline, are promising agents for the alleviation of neuropathic pain. Neoline can be used as a marker compound to determine the quality of the PA products for the treatment of neuropathic pain.

Development of a physiologically-based pharmacokinetic pediatric brain model for prediction of cerebrospinal fluid drug concentrations and the influence of meningitis

Different pediatric physiologically-based pharmacokinetic (PBPK) models have been described incorporating developmental changes that influence plasma drug concentrations. Drug disposition into cerebrospinal fluid (CSF) is also subject to age-related variation and can be further influenced by brain diseases affecting blood-brain barrier integrity, like meningitis. Here, we developed a generic pediatric brain PBPK model to predict CSF concentrations of drugs that undergo passive transfer, including age-appropriate parameters. The model was validated for the analgesics paracetamol, ibuprofen, flurbiprofen and naproxen, and for a pediatric meningitis population by empirical optimization of the blood-brain barrier penetration of the antibiotic meropenem. Plasma and CSF drug concentrations derived from the literature were used to perform visual predictive checks and to calculate ratios between simulated and observed area under the concentration curves (AUCs) in order to evaluate model performance. Model-simulated concentrations were comparable to observed data over a broad age range (3 months–15 years postnatal age) for all drugs investigated. The ratios between observed and simulated AUCs (AUCo/AUCp) were within 2-fold difference both in plasma (range 0.92–1.09) and in CSF (range 0.64–1.23) indicating acceptable model performance. The model was also able to describe disease-mediated changes in neonates and young children (<3m postnatal age) related to meningitis and sepsis (range AUCo/AUCp plasma: 1.64–1.66, range AUCo/AUCp CSF: 1.43–1.73). Our model provides a new computational tool to predict CSF drug concentrations in children with and without meningitis and can be used as a template model for other compounds that passively enter the CNS.

Developmental processes in children affect pharmacokinetics and should ideally be taken into account when establishing drug dosing regimens. One way to incorporate developmental differences is by making use of physiologically-based pharmacokinetic (PBPK) models in which kinetic equations are used to describe drug disposition processes and developmental biology. With these equations the absorption of drugs into the model, the flow of drugs between different compartments (representing major organs/tissues), and excretion from the model are predicted. PBPK models can also be used to describe drug concentrations in different target tissues, which often correlate better with the clinical effects. Here, we developed a generic pediatric PBPK model of drug disposition in the cerebrospinal fluid (CSF), that was able to describe clinically measured drug concentrations of several drugs in neonates and children. The model could be useful in predicting CSF concentrations of other drugs in pediatric populations where clinical data is often sparse or absent and by this means guide first-in-child dose recommendations.

TAT-Modified ω-Conotoxin MVIIA for Crossing the Blood-Brain Barrier

As the first in a new class of non-opioid drugs, ω-Conotoxin MVIIA was approved for the management of severe chronic pains in patients who are unresponsive to opioid therapy. Unfortunately, clinical application of MVIIA is severely limited due to its poor ability to penetrate the blood-brain barrier (BBB), reaching the central nervous system (CNS). In the present study, we have attempted to increase MVIIA’s ability to cross the BBB via a fusion protein strategy. Our results showed that when the TAT-transducing domain was fused to the MVIIA C-terminal with a linker of varied numbers of glycine, the MVIIA-TAT fusion peptide exhibited remarkable ability to cross the bio-membranes. Most importantly, both intravenous and intranasal administrations of MVIIA-TAT in vivo showed therapeutic efficacy of analgesia. Compared to the analgesic effects of intracerebral administration of the nascent MVIIA, these systemic administrations of MVIIA-TAT require higher doses, but have much prolonged effects. Taken together, our results showed that TAT conjugation of MVIIA not only enables its peripheral administration, but also maintains its analgesic efficiency with a prolonged effective time window. Intranasal administration also rendered the MVIIA-TAT advantages of easy applications with potentially reduced side effects. Our results may present an alternative strategy to improve the CNS accessibility for neural active peptides.

A Primer to Pharmacogenetics of Postoperative Pain Management

There is substantial variability in patients' response to medications. The healthcare system is in the midst of a transformation to a targeted precision health approach in which disease treatment and prevention take into account individual genetic variability. This change is informed by studies, which show that genetic variations alter the structure and function of proteins such as drug transporters, drug-metabolizing enzymes, and receptors. Tailoring medication administration based on genetic makeup can minimize adverse effects and maximize efficacy. As a result, many healthcare centers have begun incorporating genomic information into healthcare decision making. Unfortunately, many anesthesia providers may be unfamiliar with the genetics concepts and principles underlying variability in patients' response to medication. This article reviews genetic diversity in humans and the various ways in which this genetic variability may influence pharmacokinetics and pharmacodynamics of drugs. This knowledge will ensure that anesthesia providers can effectively tailor anesthesia care and postoperative pain management to improve outcomes.

Effect of Caffeine on the Bioavailability and Pharmacokinetics of an Acetylsalicylic Acid-Paracetamol Combination: Results of a Phase I Study

INTRODUCTION

Caffeine is used as an adjuvant in analgesic combinations to enhance their efficacy. The present study aimed to determine the effect of caffeine on the pharmacokinetics of acetylsalicylic acid (ASA) and paracetamol when used as a fixed-dose ASA/paracetamol/caffeine combination.

METHODS

In this single-centre, two-way, cross-over phase I study, volunteers fasted overnight (≥ 12 h) and randomly received single oral doses of 250 mg ASA/200 mg paracetamol (reference) or 250 mg ASA/200 mg paracetamol/50 mg caffeine (test). Blood samples were collected before and up to 24 h after dosing. The primary end points were the area under the concentration-time curve from zero to infinity (AUC_0-∞) and maximum plasma concentration (C_max) for ASA, salicylic acid (SA) and paracetamol from the two combinations. The main secondary end points were AUC_0-∞ and C_max of caffeine and time to reach C_max (t_max) of all drugs.

RESULTS

Eighteen healthy male volunteers (32.5 ± 10.5 years) participated in the study. The geometric means of C_max for ASA, SA and paracetamol were similar in the test (3.71, 15.8 and 2.42 µg/ml, respectively) and reference groups (3.89, 15.8, 2.42 µg/ml, respectively). The geometric mean of AUC_0-∞ for ASA, SA and paracetamol from the test combination was 2.86, 60.5 and 7.68 µg h/ml, respectively, and that for the reference was 2.96, 59.1 and 7.77 µg h/ml, respectively. The medians of t_max for ASA, SA and paracetamol were similar between the two groups. The point estimates for the ratios of AUC_0-∞ and C_max for test versus reference regarding ASA, SA and paracetamol were within the predefined equivalence limits. The two treatments were well tolerated.

CONCLUSION

Caffeine did not affect the pharmacokinetics of ASA and paracetamol when used as an adjuvant in ASA/paracetamol fixed-dose combination under fasting conditions, suggesting that caffeine enhances the analgesic efficacy of these drugs by pharmacodynamic rather than pharmacokinetic interactions.

FUNDING

Sanofi-Aventis Deutschland GmbH.

Acute Pain Management Pharmacology for the Patient with Concurrent Renal or Hepatic Disease

The clinical utility of most analgesic drugs is altered in the presence of patients with impaired renal or hepatic function not simply because of altered clearance of the parent drug, but also through production and accumulation of toxic or therapeutically active metabolites. Some analgesic agents may also aggravate pre-existing renal and hepatic disease.

A search was performed, taking in published articles and pharmaceutical data to determine available evidence for managing acute pain effectively and safely in these two patient groups. The resulting information consisted mainly of small group pharmacokinetic studies or case reports, which included a large variation in degree of organ dysfunction.

In the presence of renal impairment, those drugs which exhibit the safest pharmacological profile are alfentanil, buprenorphine, fentanyl, ketamine, paracetamol (except with compound analgesics), remifentanil and sufentanil: none of these deliver a high active metabolite load, or suffer from significantly prolonged clearance. Amitriptyline, bupivacaine, clonidine, gabapentin, hydromorphone, levobupivacaine, lignocaine, methadone, mexiletine, morphine, oxycodone and tramadol have been used in the presence of renal failure, but do require specific precautions, usually dose reduction. Aspirin, dextropropoxyphene, non-steroidal anti-inflammatory drugs and pethidine, should not be used in the presence of chronic renal failure due to the risk of significant toxicity.

In the presence of hepatic impairment, most drugs are subject to significantly impaired clearance and increased oral bioavailability, but are poorly studied in the clinical setting. The agent least subject to alteration in this context is remifentanil; however the drugs’ potency has other inherent dangers. Other agents must only be used with caution and close patient monitoring. Amitriptyline, carbamazepine and valproate should be avoided as the risk of fulminant hepatic failure is higher in this population, and methadone is contraindicated in the presence of severe liver disease.

Epibatidine: A Promising Natural Alkaloid in Health

Epibatidine is a natural alkaloid that acts at nicotinic acetylcholine receptors (nAChRs). The present review aims to carefully discuss the affinity of epibatidine and its synthetic derivatives, analogues to nAChRs for α4β2 subtype, pharmacokinetic parameters, and its role in health. Published literature shows a low affinity and lack of binding of epibatidine and its synthetic analogues to plasma proteins, indicating their availability for metabolism. Because of its high toxicity, the therapeutic use of epibatidine is hampered. However, new synthetic analogs endowed from this molecule have been developed, with a better therapeutic window and improved selectivity. All these aspects are also discussed here. On the other hand, many reports are devoted to structure⁻activity relationships to obtain optically active epibatidine and its analogues, and to access its pharmacological effects. Although pharmacological results are obtained from experimental studies and only a few clinical trials, new perspectives are open for the discovery of new drug therapies.

Injectable nanocomposite analgesic delivery system for musculoskeletal pain management

Musculoskeletal pain is a major health issue which results from surgical procedures (i.e. total knee and/or hip replacements and rotator cuff repairs), as well as from non-surgical conditions (i.e. sympathetically-mediated pain syndrome and occipital neuralgia). Local anesthetics, opioids or corticosteroids are currently used for the pain management of musculoskeletal conditions. Even though local anesthetics are highly preferred, the need for multiple administration presents significant disadvantages. Development of unique delivery systems that can deliver local anesthetics at the injection site for prolonged time could significantly enhance the therapeutic efficacy and patient comfort. The goal of the present study is to evaluate the efficacy of an injectable local anesthetic nanocomposite carrier to provide sustained analgesic effect. The nanocomposite carrier was developed by encapsulating ropivacaine, a local anesthetic, in lipid nanocapsules (LNC-Rop), and incorporating the nanocapsules in enzymatically crosslinked glycol chitosan (0.3GC) hydrogels. Cryo Scanning Electron Microscopic (Cryo SEM) images showed the ability to distribute the LNCs within the hydrogel without adversely affecting their morphology. The study demonstrated the feasibility to achieve sustained release of lipophilic molecules from the nanocomposite carrier in vitro and in vivo. A rat chronic constriction injury (CCI) pain model was used to evaluate the efficacy of the nanocomposite carrier using thermal paw withdrawal latency (TWL). The nanocomposite carriers loaded with ropivacaine and dexamethasone showed significant improvement in pain response compared to the control groups for at least 7 days. The study demonstrated the clinical potential of these nanocomposite carriers for post-operative and neuropathic pain.

STATEMENT OF SIGNIFICANCE

Acute or chronic pain associated with musculoskeletal conditions is considered a major health issue, with healthcare costs totaling several billion dollars. The opioid crisis presents a pressing clinical need to develop alternative and effective approaches to treat musculoskeletal pain. The goal of this study was to develop a long-acting injectable anesthetic formulation which can sustain a local anesthetic effect for a prolonged time. This in turn could increase the quality of life and rehabilitation outcome of patients, and decrease opioid consumption. The developed injectable nanocomposite demonstrated the feasibility to achieve prolonged pain relief in a rat chronic constriction injury (CCI) model.

Orally Available Soluble Epoxide Hydrolase/Phosphodiesterase 4 Dual Inhibitor Treats Inflammatory Pain

Inspired by previously discovered enhanced analgesic efficacy between soluble epoxide hydrolase (sEH) and phosphodiesterase 4 (PDE4) inhibitors, we designed, synthesized and characterized 21 novel sEH/PDE4 dual inhibitors. The best of these displayed good efficacy in in vitro assays. Further pharmacokinetic studies of a subset of four selected compounds led to the identification of a bioavailable dual inhibitor N-(4-methoxy-2-(trifluoromethyl)benzyl)-1-propionylpiperidine-4-carboxamide (MPPA). In a lipopolysaccharide induced inflammatory pain rat model, MPPA rapidly increased in the blood ( Tmax = 30 min; Cmax = 460 nM) after oral administration of 3 mg/kg and reduced inflammatory pain with rapid onset of action correlating with blood levels over a time course of 4 h. Additionally, MPPA does not alter self-motivated exploration of rats with inflammatory pain or the withdrawal latency in control rats.

Drug-drug interactions with aprepitant in antiemetic prophylaxis for chemotherapy

In the current guidelines to prevent hemotherapyinduced nausea and vomiting, multiple antiemetic drugs are administered simultaneously. In patients who receive highly emetogenic chemotherapy, aprepitant, an NK1-receptor antagonist, is combined with ondansetron and dexamethasone. Aprepitant can influence the pharmacokinetics of other drugs, as it is an inhibitor and inducer of CYP3A4. Some anticancer drugs and other co-medication frequently used in cancer patients are CYP3A4 or CYP29C substrates. We give an overview of the metabolism and current data on clinically relevant drug-drug interactions with aprepitant during chemotherapy. Physicians should be aware of the potential risk of drug-drug interactions with aprepitant, especially in regimens with curative intent. More research should be performed on drug-drug interactions with aprepitant and their clinical consequences to make evidence-based recommendations.

Identification of second-generation P2X3 antagonists for treatment of pain

A second-generation small molecule P2X3 receptor antagonist has been developed. The lead optimization strategy to address shortcomings of the first-generation preclinical lead compound is described herein. These studies were directed towards the identification and amelioration of preclinical hepatobiliary findings, reducing potential for drug-drug interactions, and decreasing the projected human dose of the first-generation lead.

Ultrasound-guided genicular nerve block for pain control after total knee replacement: Preliminary case series and technical note

INTRODUCTION

Total knee arthroplasty (TKA) is an operation with moderate to severe postoperative pain. The Fast-Track models employ local infiltration techniques with anaesthetics at high volumes (100-150ml). We proposed a genicular nerve block with low volume of local anaesthetic. The aim of our study is to evaluate the periarticular distribution of these blocks in a fresh cadaver model and to describe the technique in a preliminary group of patients submitted to TKA.

MATERIALS AND METHODS

In the anatomical phase, 4 genicular nerves (superior medial, superior lateral, inferior medial and inferior lateral) were blocked with 4ml of local anaesthetic with iodinated contrast and methylene blue in each (16ml in total). It was performed on a fresh cadaver and the distribution of the injected medium was evaluated by means of a CT-scan and coronal anatomical sections on both knees. The clinical phase included 12 patients scheduled for TKA. Ultrasound-guided block of the 4 genicular nerves was performed preoperatively and their clinical efficacy evaluated by assessing pain after the reversal of the spinal block and at 12h after the block. Pain was measured using the numerical scale and the need for rescue analgesia was evaluated.

RESULTS

A wide periarticular distribution of contrast was observed by CT-scan, which was later evaluated in the coronal sections. The distribution followed the joint capsule without entering the joint, both in the femur and in the tibia. The pain after the reversal of the subarachnoid block was 2±1, requiring rescue analgesia in 42% of the patients. At 12h, the pain according to the numerical scale was 4±1, 33% required rescue analgesia.

CONCLUSION

The administration of 4ml of local anaesthetic at the level of the 4 genicular nerves of the knee produces a wide periarticular distribution. Our preliminary data in a series of 12 patients undergoing TKA seems to be clinically effective. Nevertheless, extensive case series and comparative studies with local infiltration techniques with anaesthetics are needed to support these encouraging results.

[MODERN VIEWS ON THE PHARMACOGENETICS OF PAIN.]

Quality anesthesia during surgery and in the postoperative period remains a topical problem of modern anesthesiology. The study of genetic characteristics of a patient is a goal that may be allow us to develop a personalized approach to solve this problem. The purpose of the review is a synthesis of literature data about the influence of genetic factors on pain perception and its treatment. The review included information obtained from SCOPUS, MedLine, EMBASE. The search keywords were: pain, pharmacogenetics, polymorphism, analgesics.Describe the effect ofgene polymorphisms of OPRM, 5HTRIA, 5HTR2A, COMT GCHI, SCN9A, KCNSI, CACNA2D3, CACNG2, PTGSI, PTGS2, MDRJ/ABCB] on the perception of pain, and CYP2D6, CYP2C9, CYP3A4 on the pharmacokinetics and pharmacodynamics of medi- cations used in the treatment of pain.

Multi-kinetics and site-specific release of gabapentin and flurbiprofen from oral fixed-dose combination: in vitro release and in vivo food effect

In this work, a fixed-dose combination of gabapentin and flurbiprofen formulated as multilayer tablets has been designed, developed and studied in vitro and in vivo. The aim was to construct a single dosage form of the two drugs, able to perform a therapeutic program involving three release kinetics and two delivery sites, i.e., immediate release of gabapentin, intra-gastric prolonged release of gabapentin and intestinal (delayed) release of flurbiprofen. An oblong three-layer tablet was manufactured having as top layer a floating hydrophilic polymeric matrix for gastric release of gabapentin, as middle layer a disintegrating formulation for immediate release of a gabapentin loading dose and as bottom layer, an uncoated hydrophilic polymeric matrix, swellable but insoluble in gastric fluids, for delayed and prolonged release of flurbiprofen in intestinal environment. The formulations were studied in vitro and in vivo in healthy volunteers. The in vitro release rate assessment confirmed the programmed delivery design. A significant higher bioavailability of gabapentin administered 30min after meal, compared to fasting conditions or to dose administration 10min before meal, argued in favor of the gastro-retention of gabapentin prolonged release layer. The two drugs were delivered at different anatomical sites, since the food presence prolonged the gastric absorption of gabapentin from the floating layer and delayed the flurbiprofen absorption. The attainment of a successful delayed release of flurbiprofen was realized by a matrix based on a polymers' combination. The combined use of three hydrophilic polymers with different pH sensitivity provided the dosage form layer containing flurbiprofen with gastro-resistant characteristics without the use of film coating.

Polyglycerol-opioid conjugate produces analgesia devoid of side effects

Novel painkillers are urgently needed. The activation of opioid receptors in peripheral inflamed tissue can reduce pain without central adverse effects such as sedation, apnoea, or addiction. Here, we use an unprecedented strategy and report the synthesis and analgesic efficacy of the standard opioid morphine covalently attached to hyperbranched polyglycerol (PG-M) by a cleavable linker. With its high-molecular weight and hydrophilicity, this conjugate is designed to selectively release morphine in injured tissue and to prevent blood-brain barrier permeation. In contrast to conventional morphine, intravenous PG-M exclusively activated peripheral opioid receptors to produce analgesia in inflamed rat paws without major side effects such as sedation or constipation. Concentrations of morphine in the brain, blood, paw tissue, and in vitro confirmed the selective release of morphine in the inflamed milieu. Thus, PG-M may serve as prototype of a peripherally restricted opioid formulation designed to forego central and intestinal side effects.

Advanced Analgesic Drug Delivery and Nanobiotechnology

Transdermal administration of analgesic medications offers several benefits over alternative routes of administration, including a decreased systemic drug load with fewer side effects, and avoidance of drug degradation by the gastrointestinal tract. Transdermal administration also offers a convenient mode of drug administration over an extended period of time, particularly desirable in pain medicine. A transdermal administration route may also offer increased safety for drugs with a narrow therapeutic window. The primary barrier to transdermal drug absorption is the skin itself. Transdermal nanotechnology offers a novel method of achieving enhanced dermal penetration with an extended delivery profile for analgesic drugs, due to their small size and relatively large surface area. Several materials have been used to enhance drug duration and transdermal penetration. The application of nanotechnology in transdermal delivery of analgesics has raised new questions regarding safety and ethical issues. The small molecular size of nanoparticles enables drug delivery to previously inaccessible body sites. To ensure safety, the interaction of nanoparticles with the human body requires further investigation on an individual drug basis, since different formulations have unique properties and side effects.

Managing herpes zoster in older adults: Prescribing considerations

NPs must be aware of special prescribing considerations for medication safety when managing the care of older adults with herpes zoster. Age-related physiologic changes of the body impact the pharmacokinetics and pharmacodynamics of antiviral and pain medications and can lead to potential adverse events.

Development of New Benzenesulfonamides As Potent and Selective Nav1.7 Inhibitors for the Treatment of Pain

By taking advantage of certain features in piperidine 4, we developed a novel series of cyclohexylamine- and piperidine-based benzenesulfonamides as potent and selective Nav1.7 inhibitors. However, compound 24, one of the early analogs, failed to reduce phase 2 flinching in the mouse formalin test even at a dose of 100 mpk PO due to insufficient dorsal root ganglion (DRG) exposure attributed to poor membrane permeability. Two analogs with improved membrane permeability showed much increased DRG concentrations at doses of 30 mpk PO, but, confoundingly, only one of these was effective in the formalin test. More data are needed to understand the disconnect between efficacy and exposure relationships.

Randomised, double-blind, parallel group, placebo-controlled study to evaluate the analgesic efficacy and safety of VVZ-149 injections for postoperative pain following laparoscopic colorectal surgery

INTRODUCTION

In spite of advances in understanding and technology, postoperative pain remains poorly treated for a significant number of patients. In colorectal surgery, the need for developing novel analgesics is especially important. Patients after bowel surgery are assessed for rapid return of bowel function and opioids worsen ileus, nausea and constipation. We describe a prospective, double-blind, parallel group, placebo-controlled randomised controlled trial testing the hypothesis that a novel analgesic drug, VVZ -149, is safe and effective in improving pain compared with providing opioid analgesia alone among adults undergoing laparoscopic colorectal surgery.

METHODS AND ANALYSIS

Based on sample size calculations for primary outcome, we plan to enrol 120 participants. Adult patients without significant medical comorbidities or ongoing opioid use and who are undergoing laparoscopic colorectal surgery will be enrolled. Participants are randomly assigned to receive either VVZ-149 with intravenous (IV) hydromorphone patient-controlled analgesia (PCA) or the control intervention (IV PCA alone) in the postoperative period. The primary outcome is the Sum of Pain Intensity Difference over 8 hours (SPID-8 postdose). Participants receive VVZ-149 for 8 hours postoperatively to the primary study end point, after which they continue to be assessed for up to 24 hours. We measure opioid consumption, record pain intensity and pain relief, and evaluate the number of rescue doses and requests for opioid. To assess safety, we record sedation, nausea and vomiting, respiratory depression, laboratory tests and ECG readings after study drug administration. We evaluate for possible confounders of analgesic response, such as anxiety, depression and catastrophising behaviours. The study will also collect blood sample data and evaluate for pharmacokinetic and pharmacodynamic relationships.

ETHICS AND DISSEMINATION

Ethical approval of the study protocol has been obtained from Institutional Review Boards at the participating institutions. Trial results will be disseminated through scientific conference presentations and by publication in scientific journals.

TRIAL REGISTRATION NUMBER

NCT02489526; pre-results.

Medicinal Chemistry of σ1 Receptor Ligands: Pharmacophore Models, Synthesis, Structure Affinity Relationships, and Pharmacological Applications

In the first part of this chapter, we summarize the various pharmacophore models for σ1 receptor ligands. Common to all of them is a basic amine flanked by two hydrophobic regions, representing the pharmacophoric elements. The development of computer-based models like the 3D homology model is described as well as the first crystal structure of the σ1 receptor. The second part focuses on the synthesis and biological properties of different σ1 receptor ligands, identified as 1-9. Monocyclic piperazines 1 and bicyclic piperazines 2 and 3 were developed as cytotoxic compounds, thus the IC50 values of cell growth and survival inhibition studies are given for all derivatives. The mechanism of cell survival inhibition, induction of time-dependent apoptosis, of compound ent-2a is discussed. Experimentally determined σ1 affinity shows good correlation with the results from molecular dynamics simulations based on a 3D homology model. Spirocyclic compounds 4 and 5 represent well-established σ1 receptor ligands. The homologous fluoroalkyl derivatives 4 have favorable pharmacological properties for use as fluorinated PET tracers. The (S)-configured fluoroethyl substituted compound (S)-4b is under investigation as PET tracer for imaging of σ1 receptors in the brain of patients affected by major depression. 1,3-Dioxanes 6c and 6d display a very potent σ1 antagonist profile and the racemic 1,3-dioxane 6c has high anti-allodynic activity at low doses. The arylpropenylamines 7 are very potent σ1 receptor ligands with high σ1/σ2 selectivity. The top compound 7g acts as an agonist as defined by its ability to potentiate neurite outgrowth at low concentrations. Among the morpholinoethoxypyrazoles 8, 8c (known as S1RA) reveals the most promising pharmacokinetic and physicochemical properties. Due to its good safety profile, 8c is currently being investigated in a phase II clinical trial for the treatment of neuropathic pain. The most potent ligand 9e of 3,4-dihydro-2(1H)-quinolones 9 shows promising anti-nociceptive activity in the formalin test.

Prolonged infusion of sedatives and analgesics in adult intensive care patients: A systematic review of pharmacokinetic data reporting and quality of evidence

Although pharmacokinetic (PK) data for prolonged sedative and analgesic agents in intensive care unit (ICU) has been described, the number of publications in this important area appear relatively few, and PK data presented is not comprehensive. Known pathophysiological changes in critically ill patients result in altered drug PK when compared with non-critically ill patients. ClinPK Statement was recently developed to promote consistent reporting in PK studies, however, its applicability to ICU specific PK studies is unclear. In this systematic review, we assessed the overall ClinPK Statement compliance rate, determined the factors affecting compliance rate, graded the level of PK evidence and assessed the applicability of the ClinPK Statement to future ICU PK studies. Of the 33 included studies (n=2016), 22 (67%) were low evidence quality descriptive studies (Level 4). Included studies had a median compliance rate of 80% (IQR 66% to 86%) against the ClinPK Statement. Overall pooled compliance rate (78%, 95% CI 73% to 83%) was stable across time (P=0.38), with higher compliance rates found in studies fitting three compartments models (88%, P<0.01), two compartments models (83%, P<0.01) and one compartment models (77%, P=0.17) than studies fitting noncompartmental or unspecified models (69%) (P<0.01). Data unique to the interpretation of PK data in critically ill patients, such as illness severity (48%), organ dysfunction (36%) and renal replacement therapy use (32%), were infrequently reported. Discrepancy between the general compliance rate with ClinPK Statement and the under-reporting of ICU specific parameters suggests that the applicability of the ClinPK Statement to ICU PK studies may be limited in its current form.

An Expert Review of Pharmacogenomics of Sickle Cell Disease Therapeutics: Not Yet Ready for Global Precision Medicine

Sickle cell disease (SCD) is a blood disease caused by a single nucleotide substitution (T > A) in the beta globin gene on chromosome 11. The single point mutation (Glu6Val) promotes polymerization of hemoglobin S (HbS) and causes sickling of erythrocytes. Vaso-occlusive painful crises are associated with recurrent and long-term use of analgesics/opioids and hydroxyurea (HU) by people living with SCD. The present analysis offers a state-of-the-art expert review of the effectiveness of pharmacogenomics/genetics of pain management in SCD, with specific focus on HU and opioids. The literature search used the following keywords: SCD, pharmacogenomics, pharmacogenetics, pain, antalgics, opioids, morphine, and HU. The literature was scanned until March 2016, with specific inclusion of targeted landmark and background articles on SCD. Surprisingly, our review identified only a limited number of studies that addressed the genetic/genomic basis of variable responses to pain (e.g., variants in OPRM1, HMOX-1, GCH1, VEGFA COMT genes), and pharmacogenomics of antalgics and opioids (e.g., variants in OPRM1, STAT6, ABCB1, and COMT genes) in SCD. There has been greater progress made toward identifying the key genomic variants, mainly in BCL11A, HBS1L-MYB, or SAR1, which contribute to response to HU treatment. However, the complete picture on pharmacogenomic determinants of the above therapeutic phenotypes remains elusive. Strikingly, no study has been conducted in sub-Saharan Africa where majority of the patients with SCD live. This alerts the broader global life sciences community toward the existing disparities in optimal and ethical targeting of research and innovation investments for SCD specifically and precision medicine and pharmacology research broadly.

Outcome of Medication Overuse Headache after Abrupt in-Patient withdrawal

One hundred and one patients suffering from chronic daily headache (CDH) and medication overuse were treated, in an in-patient setting, with abrupt discontinuation of the medication overused, intravenous hydrating, and intravenous administration of benzodiazepines and ademetionine. The mean time to CDH resolution was 8.8 days. The in-patient withdrawal protocol used was effective, safe and well tolerated. There was a trend for a shorter time to CDH resolution in patients who overused triptans ( P = 0.062). There was no correlation between time to CDH resolution and either the type of initial primary headache or duration of medication abuse, whereas time to CDH resolution was related to daily drug intake ( P = 0.01). In multiple regression analysis, daily drug intake, age and type of medication overused were independent predictors of time to CDH resolution. At 3-months' follow-up, no patient had relapsed and was again overusing symptomatic medications.

Effect of Penetration Enhancers on the Percutaneous Delivery of Pain Management Actives

Transdermal compositions for pain management are comprised of nonsteroidal anti-inflammatory drugs, opioid drugs, and adjuvant drugs acting on: voltage-gated channels, gamma-aminobutyric acid receptors, acute musculoskeletal pain, and as an antidepressant. In this work, baclofen, bupivacaine, cyclobenzaprine, diclofenac, gabapentin, ibuprofen, ketamine, and pentoxifylline were loaded in transdermal compositions, prepared using a mixture of lipids (isopropyl palmitate and mineral oil) and one of two selected penetration enhancer mixtures: alkyl dimethicone, phenyl trimethicone, and polyoxyethylene sorbitan monostearate; and cetostearyl polyoxyethylene ether and ethylene oxide/propylene oxide copolymer. The influence of penetration enhancers on transdermal delivery was evaluated using Franz-type diffusion cells and Normal Human 3D Model of Epidermal Tissue. Results showed that drug delivery is affected by the penetration enhancer used in the transdermal composition.

Bioavailability of paracetamol with/without caffeine in Egyptian patients with hepatitis C virus

PURPOSE

This study investigates the involvement of liver dysfunction in the modulation of paracetamol pharmacokinetic profile in genotype-4 HCV patients treated with either paracetamol alone (Para) or in combination with caffeine (Para-Caf).

METHODS

Twenty healthy volunteers and 20 Child-Pugh B HCV patients, each divided into two equal subgroups, were examined, whose liver/kidney functions were correlated with their main clinical manifestation. After an overnight fasting, healthy and hepatic subjects received either a single dose of Para (1000 mg paracetamol) or Para-Caf (1000 mg paracetamol/130 mg caffeine). Two milliliters of saliva samples were collected prior to and at different time-intervals after drug administration and analyzed using HPLC.

RESULTS

There was a noticeable increase in the mean concentration time profile of salivary paracetamol concentrations in hepatic patients, with concomitant decrease in paracetamol clearance (CLT), along with induction in the primary pharmacokinetic (PK) parameters, C max, AUC(0-8 h) and AUC(0-∞) (by about 95, 82, and 64 %, respectively, after treatment with Para, and 98, 96, and 101 %, respectively, after treatment with Para-Caf), when compared with the corresponding parameters in healthy subjects. Additionally, the healthy subjects treated with Para-Caf exhibited bioinequivalent increase in C max, K a, and t 1/2 with decrease in T max when compared with the healthy individuals treated with Para alone. A similar pattern was recorded in hepatic patients after addition of caffeine to paracetamol, with even augmented significant increase in K a and t 1/2 (by 100 and 32 %, respectively).

CONCLUSIONS

Liver dysfunction modified the PK of paracetamol expressed as earlier effective paracetamol concentration, with obvious decrease in its clearance. Caffeine induced faster absorption (evidenced by shorter T max and higher K a) and prolonged t 1/2 of paracetamol, the effects that were more profound in hepatic patients. Further studies are needed to evaluate the influence of liver damage on paracetamol pharmacokinetics whenever repeated dosing is applied, to avoid possible drug accumulation.

Analgesic Effect of the Newly Developed S(+)-Flurbiprofen Plaster on Inflammatory Pain in a Rat Adjuvant-Induced Arthritis Model

Preclinical Research This article describes the properties of a novel topical NSAID (Nonsteroidal anti-inflammatory drug) patch, SFPP (S(+)-flurbiprofen plaster), containing the potent cyclooxygenase (COX) inhibitor, S(+)-flurbiprofen (SFP). The present studies were conducted to confirm human COX inhibition and absorption of SFP and to evaluate the analgesic efficacy of SFPP in a rat adjuvant-induced arthritis (AIA) model. COX inhibition by SFP, ketoprofen and loxoprofen was evaluated using human recombinant COX proteins. Absorption of SFPP, ketoprofen and loxoprofen from patches through rat skin was assessed 24 h after application. The AIA model was induced by injecting Mycobacterium tuberculosis followed 20 days later by the evaluation of the prostaglandin PGE2 content of the inflamed paw and the pain threshold. SFP exhibited more potent inhibitory activity against COX-1 (IC50  = 8.97 nM) and COX-2 (IC50  = 2.94 nM) than the other NSAIDs evaluated. Absorption of SFP was 92.9%, greater than that of ketoprofen and loxoprofen from their respective patches. Application of SFPP decreased PGE2 content from 15 min to 6 h and reduced paw hyperalgesia compared with the control, ketoprofen and loxoprofen patches. SFPP showed analgesic efficacy, and was superior to the ketoprofen and loxoprofen patches, which could be through the potent COX inhibitory activity of SFP and greater skin absorption. The results suggested SFPP can be expected to exert analgesic effect clinically.

Pharmacokinetics of Compounded Intravenous and Oral Gabapentin in Hispaniolan Amazon Parrots ( Amazona ventralis )

Neuropathic pain is a manifestation of chronic pain that arises with damage to the somatosensory system. Pharmacologic treatment recommendations for alleviation of neuropathic pain are often multimodal, and the few reports communicating treatment of suspected neuropathic pain in avian patients describe the use of gabapentin as part of the therapeutic regimen. To determine the pharmacokinetics of gabapentin in Hispaniolan Amazon parrots ( Amazona ventralis ), compounded gabapentin suspensions were administered at 30 mg/kg IV to 2 birds, 10 mg/kg PO to 3 birds, and 30 mg/kg PO to 3 birds. Blood samples were collected immediately before and at 9 different time points after drug administration. Plasma samples were analyzed for gabapentin concentration, and pharmacokinetic parameters were calculated with both a nonlinear mixed-effect approach and a noncompartmental analysis. The best compartmental, oral model was used to simulate the concentration-time profiles resulting from different dosing scenarios. Mild sedation was observed in both study birds after intravenous injection. Computer simulation of different dosing scenarios with the mean parameter estimates showed that 15 mg/kg every 8 hours would be a starting point for oral dosing in Hispaniolan Amazon parrots based on effective plasma concentrations reported for human patients; however, additional studies need to be performed to establish a therapeutic dose.

[Clonidine can reduce opioid medication during post-operative pain]

Post-operative pain management can be a challenge, and one of the first choices seems to be opioids. However, opioids have undesirable side effects, and attention may lead to a multimodal analgesia. The use of clonidine is a part of this strategy. We present a study with assessment of routes of administration of clonidine. Overall, there is a good effect of post-operative pain management. Side effects as hypotension and sedation are mentioned but not as a limitation. Many anaesthesiologists do already use clonidine in the management of post-operative pain, but more research about intravenous administration of clonidine is needed.

In vitro and in vivo evaluation of capsaicin-loaded microemulsion for enhanced oral bioavailability

BACKGROUND

Capsaicin, as a food additive, has attracted worldwide concern owing to its pungency and multiple pharmacological effects. However, poor water solubility and low bioavailability have limited its application. This study aims to develop a capsaicin-loaded microemulsion to enhance the oral bioavailability of the anti-neuropathic-pain component, capsaicin, which is poorly water soluble.

RESULTS

In this study, the microemulsion consisting of Cremophor EL, ethanol, medium-chain triglycerides (oil phase) and water (external phase) was prepared and characterized (particle size, morphology, stability and encapsulation efficiency). The gastric mucosa irritation test of formulated capsaicin was performed in rats to evaluate its oral feasibility, followed by the pharmacokinetic study in vivo. Under these conditions, the encapsulated capsaicin revealed a faster capsaicin release in vitro coupled with a greater absorption in vivo when compared to the free capsaicin. The oral bioavailability of the formulated capsaicin-loaded microemulsions was 2.64-fold faster than that of free capsaicin. No significant irritation was observed on the mucosa from the pathological section of capsaicin-loaded microemulsion treated stomach.

CONCLUSION

These results indicate that the developed microemulsion represents a safe and orally effective carrier for poorly soluble substances. The formulation could be used for clinical trials and expand the application of capsaicin.

Distribution in Rats Internal Organs of Intraperitoneally Given 125I-Labeled Heptapeptide [2-8]-Leucopyrokinin ([2-8]-LPK), a Truncated Analog of Insect Neuropeptide Leucopyrokinin

BACKGROUND

It was previously found that synthetic, insect-derived octapeptide leucopyrokinin (LPK) applied directly into the lateral brain ventricle induced a significant antinociceptive effect in rats. Its synthetic truncated analog heptapeptide [2-8]-leucopyrokinin displayed a stronger antinociceptive effect in comparison to native LPK. Moreover it was previously found a high accumulation of these both 125I-labeled peptides in adrenals, as well as in hypothalamus and in hippocampus of rats brain.

OBJECTIVES

The aim of the present study was to assess the distribution of 125I-labeled [2-8]-leucopyrokinin in rats' internal organs an in several parts of the brain after peripheral - intraperitoneal (i.p.) administration.

MATERIAL AND METHODS

The study was performed on male Wistar rats. A synthetic [2-8]-leucopyrokinin ([2-8]-LPK) was iodinated with Na125I. On the day of experiment a solution of 125I-[2-8]-LPK was i.p. injected and the next after 1 and 24 h animals were sacrificed by decapitation. Radioactivity levels in samples of parts of the brain and of internal organs were determined by counter Gamma Auto Count.

RESULTS

A uniform, low accumulation 125I-[2-8]-LPK was found in evaluated samples of the brain and in internal organs.

CONCLUSIONS

The results of the present study indicate a weak penetration into the brain and internal organs of intraperitoneally applied 125I-[2-8]-LPK in rats and correspond with previously determined weak biological effects of i.p. injected LPK and [2-8]-LPK.

Botulinum Toxin as a Pain Killer: Players and Actions in Antinociception

Botulinum neurotoxins (BoNTs) have been widely used to treat a variety of clinical ailments associated with pain. The inhibitory action of BoNTs on synaptic vesicle fusion blocks the releases of various pain-modulating neurotransmitters, including glutamate, substance P (SP), and calcitonin gene-related peptide (CGRP), as well as the addition of pain-sensing transmembrane receptors such as transient receptor potential (TRP) to neuronal plasma membrane. In addition, growing evidence suggests that the analgesic and anti-inflammatory effects of BoNTs are mediated through various molecular pathways. Recent studies have revealed that the detailed structural bases of BoNTs interact with their cellular receptors and SNAREs. In this review, we discuss the molecular and cellular mechanisms related to the efficacy of BoNTs in alleviating human pain and insights on engineering the toxins to extend therapeutic interventions related to nociception.

Pharmacokinetics of mitragynine in man

BACKGROUND

Kratom, known botanically as Mitragyna speciosa (Korth.), is an indigenous tree in Southeast Asia. Kratom is currently easily available worldwide via special shops and the Internet to use as a drug of abuse, opioid alternative, or pain killer. So far, the pharmacokinetics of this plant has been studied only in animals, and there is no such study in humans. The major abundant active alkaloid in Kratom, mitragynine, is one of the promising new chemical substances to be developed as a new drug. The aim of this study was to examine the pharmacokinetics of mitragynine and assess the linearity in pharmacokinetics in chronic users.

METHODS

Since Kratom is illegal in Thailand, studies in healthy subjects would be unethical. We therefore conducted a prospective study by enrolling ten chronic, regular, healthy users. We adjusted the steady state in each subject by giving a known amount of Kratom tea for 7 days before commencement of the experiment. We admitted and gave different oral doses to subjects to confirm linearity in pharmacokinetics. The mitragynine blood concentrations at 17 times points and the urine concentrations during the 24-hour period were collected and measured by liquid chromatography-tandem mass spectrometry method.

RESULTS

Ten male subjects completed the study without adverse reactions. The median duration of abuse was 1.75 years. We analyzed one subject separately due to the abnormal behavior of blood concentration. From data of nine subjects, the pharmacokinetic parameters established were time to reach the maximum plasma concentration (0.83±0.35 hour), terminal half-life (23.24±16.07 hours), and the apparent volume of distribution (38.04±24.32 L/kg). The urine excretion of unchanged form was 0.14%. The pharmacokinetics were observed to be oral two-compartment model.

CONCLUSION

This was the first pharmacokinetic study in humans, which demonstrated linearity and was consistent with the oral two-compartment model with a terminal half-life of about 1 day. The pharmacokinetic linearity and parameters reported are necessary pharmacological information of Kratom, and there is a possibility for it to be developed medically as a pain killer or better opioid substitute in the future.

Preparation, characterization, and pharmacokinetics study of capsaicin via hydroxypropyl-beta-cyclodextrin encapsulation

CONTEXT

Capsaicin (CAP) is an effective drug in the treatment of pain and cancer. However, its practical administration has been limited due to poor aqueous solubility and bioavailability, as well as strong gastrointestinal irritation.

OBJECTIVE

The objective of this study is to improve the solubility and oral bioavailability of CAP by reducing irritation via hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complex formulation, in vitro and in vivo analysis.

MATERIALS AND METHODS

The complex (CAP-HP-β-CD) was developed via the magnetic stirring method and characterized using ultraviolet (UV) absorption spectrometry, infrared radiation (IR) spectroscopy, and differential scanning calorimetry (DSC). Rats were treated with CAP (90 mg × kg(-1)) or CAP-HP-β-CD (corresponding to 90 mg × kg(-1) CAP) by gavage, and all the plasma samples were analyzed with high performance liquid chromatography (HPLC).

RESULTS

The results of UV, IR, and DSC showed that an acceptable CAP-HP-β-CD (encapsulation efficiency, 75.83%; drug loading, 7.44%) was formulated. In vitro release study of CAP-HP-β-CD revealed that the cumulative release of CAP from HP-β-CD encapsulation was obviously enhanced (above 80% increases). Similarly, the in vivo pharmacokinetics parameters also increased, Cmax (from 737.94 to 1117.57 ng × mL(-1)), AUC0- (from 5285.9 to 7409.8 ng × h × mL(-1)) or relative bioavailability (139.38%). The gastric irritation bioassay further showed that the CAP-HP-β-CD was far better than free CAP.

DISCUSSION AND CONCLUSION

CAP exhibited significant aqueous solubility and oral bioavailability, as well as minimal irritation effect after forming inclusion complex with HP-β-CD. Therefore, these findings could provide an equally important alternative option for the clinical use of CAP.