Administration of a co-crystal of tramadol and celecoxib in a 1:1 molecular ratio produces synergistic antinociceptive effects in a postoperative pain model in rats

Analgesic Effect of Sulforaphane: A New Application for Poloxamer-Hyaluronic Acid Hydrogels

Sulforaphane (SFN) has shown potential as an antioxidant and anti-inflammatory agent. To improve its druggability, we developed new analgesic formulations with sulforaphane-loaded hyaluronic acid (HA)-poloxamer (PL) hydrogel. This study evaluated the pre-clinical safety and effectiveness of these formulations. Effectiveness was tested on Wistar rats divided into groups (n = 15) receiving (IM, 10 mg/kg) SFN formulations or control groups (without SFN). This study used a hind paw incision postoperative pain model to evaluate mechanical hypersensitivity with von Frey filaments. TNF-α, IL-1β, substance P, and CGRP levels verified anti-inflammatory activity in the hind paw tissue. Histopathology of tissues surrounding the injection site was assessed after 2 and 7 days post-treatment. To corroborate drug safety, cell viability of 3T3 and RAW 264.7 cultures was assessed. Additionally, RAW 264.7 cultures primed with carrageenan evaluated nitric oxide (NO) levels. All animals exhibited post-incisional hypersensitivity, and F2 (PL 407/338 (18/2%) + HA 1% + SFN 0.1%) showed a longer analgesic effect (p < 0.05). F2 reduced TNF-α, IL-1β, and CGRP levels (p < 0.05). Histopathological evaluation showed mild to moderate inflammatory reactions after the formulations' injections. F2 produced no significant difference in cell viability (p > 0.05) but reduced NO production (p < 0.05). Thus, our results highlight the biocompatibility and effectiveness of F2.

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

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

Co-crystal of tramadol-celecoxib (CTC) for acute moderate-to-severe pain

OBJECTIVE

This narrative review aims to provide a clinical perspective on the potential role of co-crystal of tramadol-celecoxib (CTC) in the management of acute moderate-to-severe pain by synthesizing the available preclinical and clinical data, with emphasis on phase 3 trials.

METHODS

A non-systematic literature review was performed using a targeted PubMed search for articles published between January 1, 2000, and May 2, 2023; all publication types were permitted, and selected articles were limited to those published in English. Search results were manually reviewed to identify references based on their preclinical and clinical relevance to CTC and management of acute moderate-to-severe pain.

RESULTS

The crystalline structure of CTC alters the physicochemical properties of tramadol and celecoxib, modifying their pharmacokinetics. If taken in a free combination, tramadol reduces absorption of celecoxib. Conversely, administration of CTC slows tramadol absorption and lowers its maximum plasma concentration, while increasing celecoxib plasma concentration through its enhanced release. In clinical studies across models of acute moderate-to-severe pain, CTC demonstrated an early onset of analgesia, with improved efficacy and lower rescue medication use, compared with either agent alone. CTC's safety profile was in line with that expected for the individual components; no additive effects were observed. CTC exhibited tramadol-sparing effects, with efficacy seen at lower daily/cumulative opioid doses vs. tramadol alone.

CONCLUSIONS

Results from phase 3 trials suggest that the modified physicochemical properties of tramadol and celecoxib in CTC translate into an improved clinical benefit-risk profile, including fewer opioid-related adverse effects due to lower overall opioid dosing.

Combination Drug Therapy for the Management of Chronic Neuropathic Pain

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

Eco-friendly simultaneous multi-spectrophotometric estimation of the newly approved drug combination of celecoxib and tramadol hydrochloride tablets in its dosage form

Food and Drug Administration (FDA) recently approved co-formulated celecoxib and tramadol for the treatment of acute pain in adults. Three spectrophotometric methods were efficiently applied to estimate the co-formulated Celecoxib and Tramadol in their tablets; second derivative 2D-spectrophotometry technique (method I), induced dual-wavelength technique (method II) and dual-wavelength resolution technique (method III). The proposed methods were successfully validated following the International Council for Harmonisation (ICH) guidelines and statistically assessed based on the correlation coefficients, relative standard deviations as well as detection and quantitation limits. The obtained results revealed non-significant differences compared to the reported results as revealed by the variance ratio F test and Student t test. Moreover, the applied techniques were further assessed concerning their greenness based on the analytical eco-scale method revealing an excellent green scale with a final score of 95. The proposed spectrophotometric techniques could be applied for the routine analysis and quality control of the studied drugs in their dosage form.

Ketoprofen, lysine and gabapentin co-crystal magnifies synergistic efficacy and tolerability of the constituent drugs: Pre-clinical evidences towards an innovative therapeutic approach for neuroinflammatory pain

Chronic pain is an enormous public health concern, and its treatment is still an unmet medical need. Starting from data highlighting the promising effects of some nonsteroidal anti-inflammatory drugs in combination with gabapentin in pain treatment, we sought to combine ketoprofen lysine salt (KLS) and gabapentin to obtain an effective multimodal therapeutic approach for chronic pain. Using relevant in vitro models, we first demonstrated that KLS and gabapentin have supra-additive effects in modulating key pathways in neuropathic pain and gastric mucosal damage. To leverage these supra-additive effects, we then chemically combined the two drugs via co-crystallization to yield a new compound, a ternary drug-drug co-crystal of ketoprofen, lysine and gabapentin (KLS-GABA co-crystal). Physicochemical, biodistribution and pharmacokinetic studies showed that within the co-crystal, ketoprofen reaches an increased gastrointestinal solubility and permeability, as well as a higher systemic exposure in vivo compared to KLS alone or in combination with gabapentin, while both the constituent drugs have increased central nervous system permeation. These unique characteristics led to striking, synergistic anti-nociceptive and anti-inflammatory effects of KLS-GABA co-crystal, as well as significantly reduced spinal neuroinflammation, in translational inflammatory and neuropathic pain rat models, suggesting that the synergistic therapeutic effects of the constituent drugs are further boosted by the co-crystallization. Notably, while strengthening the therapeutic effects of ketoprofen, KLS-GABA co-crystal showed remarkable gastrointestinal tolerability in both inflammatory and chronic neuropathic pain rat models. In conclusion, these results allow us to propose KLS-GABA co-crystal as a new drug candidate with high potential clinical benefit-to-risk ratio for chronic pain treatment.

Cocrystals by Design: A Rational Coformer Selection Approach for Tackling the API Problems

Active pharmaceutical ingredients (API) with unfavorable physicochemical properties and stability present a significant challenge during their processing into final dosage forms. Cocrystallization of such APIs with suitable coformers is an efficient approach to mitigate the solubility and stability concerns. A considerable number of cocrystal-based products are currently being marketed and show an upward trend. However, to improve the API properties by cocrystallization, coformer selection plays a paramount role. Selection of suitable coformers not only improves the drug’s physicochemical properties but also improves the therapeutic effectiveness and reduces side effects. Numerous coformers have been used till date to prepare pharmaceutically acceptable cocrystals. The carboxylic acid-based coformers, such as fumaric acid, oxalic acid, succinic acid, and citric acid, are the most commonly used coformers in the currently marketed cocrystal-based products. Carboxylic acid-based coformers are capable of forming the hydrogen bond and contain smaller carbon chain with the APIs. This review summarizes the role of coformers in improving the physicochemical and pharmaceutical properties of APIs, and deeply explains the utility of afore-mentioned coformers in API cocrystal formation. The review concludes with a brief discussion on the patentability and regulatory issues related to pharmaceutical cocrystals.

Bispecific sigma-1 receptor antagonism and mu-opioid receptor partial agonism: WLB-73502, an analgesic with improved efficacy and safety profile compared to strong opioids

Opioids are the most effective painkillers, but their benefit-risk balance often hinder their therapeutic use. WLB-73502 is a dual, bispecific compound that binds sigma-1 (S1R) and mu-opioid (MOR) receptors. WLB-73502 is an antagonist at the S1R. It behaved as a partial MOR agonist at the G-protein pathway and produced no/unsignificant β-arrestin-2 recruitment, thus demonstrating low intrinsic efficacy on MOR at both signalling pathways. Despite its partial MOR agonism, WLB-73502 exerted full antinociceptive efficacy, with potency superior to morphine and similar to oxycodone against nociceptive, inflammatory and osteoarthritis pain, and superior to both morphine and oxycodone against neuropathic pain. WLB-73502 crosses the blood-brain barrier and binds brain S1R and MOR to an extent consistent with its antinociceptive effect. Contrary to morphine and oxycodone, tolerance to its antinociceptive effect did not develop after repeated 4-week administration. Also, contrary to opioid comparators, WLB-73502 did not inhibit gastrointestinal transit or respiratory function in rats at doses inducing full efficacy, and it was devoid of proemetic effect (retching and vomiting) in ferrets at potentially effective doses. WLB-73502 benefits from its bivalent S1R antagonist and partial MOR agonist nature to provide an improved antinociceptive and safety profile respect to strong opioid therapy.

Efficacy and safety of co-crystal of tramadol-celecoxib (CTC) in acute moderate-to-severe pain after abdominal hysterectomy: A randomized, double-blind, phase 3 trial (STARDOM2)

BACKGROUND

STARDOM2 is a randomized, double-blind, phase 3 trial evaluating the efficacy and safety of co-crystal of tramadol-celecoxib (CTC)-a first-in-class analgesic co-crystal comprising racemic tramadol hydrochloride and celecoxib in a supramolecular network that modifies their pharmacokinetic properties-for the management of acute postoperative pain (NCT03062644; EudraCT:2016-000593-38).

METHODS

Patients with moderate-to-severe pain following abdominal hysterectomy were randomized 2:2:2:2:2:1 to oral CTC 100 mg (rac-tramadol hydrochloride 44 mg/celecoxib 56 mg) twice daily (BID); CTC 150 mg (66/84 mg) BID; CTC 200 mg (88/112 mg) BID; immediate-release tramadol 100 mg four times daily (QID); celecoxib 100 mg BID; or placebo, for 5 days. The primary endpoint was the sum of pain intensity differences over 0-4 h (SPID_0-4 ). Key secondary endpoints were rescue medication use within 4 h, 50% response rate at 4 h, and safety/tolerability.

RESULTS

Of 1355 patients enrolled, 1138 were randomized (full analysis set) and 1136 treated (safety analysis set). In the prespecified gatekeeping analysis of SPID_0-4 , CTC 200 mg was not superior to tramadol but showed non-inferior efficacy (p < 0.001) that was sustained throughout the 120-h period, despite a 5-day cumulative tramadol administration of 880 mg with CTC 200 mg BID versus 2000 mg with tramadol 100 mg QID. Treatment-emergent adverse events (TEAEs) and severe TEAEs were less common with CTC 200 mg versus tramadol. Treatment-related TEAEs were 14.4% with CTC 200 mg and 23.6% with tramadol.

CONCLUSIONS

Although the study did not meet its primary endpoint, CTC 200 mg showed a clinically relevant improvement in overall benefit/risk profile versus tramadol alone, with considerably lower cumulative opioid exposure.

SIGNIFICANCE

In the randomized, double-blind, phase 3 STARDOM2 trial-in acute moderate-to-severe pain after abdominal hysterectomy-the novel co-crystal of tramadol-celecoxib (CTC) 200 mg BID was superior to placebo and non-inferior to tramadol 100 mg QID. Although superiority to tramadol was not reached, CTC 200 mg BID exposed patients to lower cumulative opioid (tramadol) doses than tramadol (100 mg QID) alone, with fewer treatment-emergent adverse events. CTC 200 mg thus has a clinically relevant improved benefit/risk profile compared with tramadol alone.

A co-crystal berberine-ibuprofen improves obesity by inhibiting the protein kinases TBK1 and IKKɛ

Berberine (BBR) exerts specific therapeutic effects on various diseases such as diabetes, obesity, and other inflammation-associated diseases. However, the low oral bioavailability (below 1%) of berberine due to its poor solubility and membrane permeability limits its clinical use. In this paper, we have prepared a 1:1 co-crystal berberine-ibuprofen (BJ) using drug salt metathesis and co-crystal technology. Pharmacokinetic studies demonstrate a 3-fold increase in vivo bioavailability of BJ compared to that of BBR, and BJ is more effective in treating obesity and its related metabolism in vitro and in vivo. We also find that BJ promotes mitochondrial biogenesis by inhibiting TBK1 and inducing AMP-activated protein kinase (AMPK) phosphorylation, and BJ increases adipocyte sensitivity to catecholamine by inhibiting IKKε. Together, our findings support that co-crystal BJ is likely to be an effective agent for treating obesity and its related metabolic diseases targeting TBK1 and IKKε.

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.

Co-crystals as a new approach to multimodal analgesia and the treatment of pain

Pain is highly prevalent, but frequently untreated or under-treated, and health care professionals are faced with a range of treatment challenges. Multimodal therapy is recommended and can be achieved using open combinations (ie, concomitant administration) of individual agents, fixed-dose combinations (FDCs), or multimodal agents (ie, single agents with multiple mechanisms of action). Co-crystallization of active pharmaceutical ingredients (APIs) offers another approach, with the potential to provide drugs with unique properties and advantages for therapeutic applications compared to combinations. API–API co-crystals are single-entity forms that offer a unique possibility of improving the physicochemical properties of both constituent APIs, as well as permitting their synchronous release. Consequently, this may positively impact on their pharmacokinetic (PK) properties and profiles, providing a potential advantage over FDCs and translating into improved clinical efficacy and safety profiles. We report here a revision of the literature concerning API–API co-crystals for the treatment of pain. It becomes apparent that identifying APIs with complementary mechanisms of action that can be adequately co-crystallized in an appropriate molecular ratio applicable for therapeutic use is challenging. In addition, API–API co-crystals normally result in a mere increased exposure of an API without defined clinical benefits (since, to maintain the benefit-risk, the dose needs to be proportionally reduced to adjust for the increased exposure). An exception to this is the co-crystal of tramadol-celecoxib (CTC), that represents a unique concept in co-crystal technology. In CTC neither of its three active components that have complementary mechanisms of action (ie, the two enantiomers of tramadol and celecoxib) show increased exposure levels versus commercially available single-entity reference products, but rather show a change in their PK profile with potential clinical advantages. CTC is in Phase III clinical development for the treatment of pain.

Co-crystal of tramadol-celecoxib: preclinical and clinical evaluation of a novel analgesic

INTRODUCTION

Pain management is a major unmet need due to the suboptimal efficacy and undesirable side effects of current analgesics. Multimodal therapies recruiting complementary mechanisms of action may help address this. Co-crystals incorporating two active pharmaceutical ingredients (APIs) constitute an innovative approach to multimodal therapy, particularly if modification of the physicochemical properties of constituent APIs can be translated into clinical benefits.

AREAS COVERED

The preclinical and clinical profiles of Co-Crystal of Tramadol-Celecoxib (CTC), a novel API-API co-crystal (1:1 molecular ratio of rac-tramadol.hydrochloride and celecoxib) are described.

EXPERT OPINION

CTC may provide a relevant addition to pain therapy due to its: i) unique co-crystal structure conferring differentiated intrinsic dissolution profiles on constituent APIs, ii) modified clinical pharmacokinetics (slower absorption of tramadol and faster absorption of celecoxib) compared with commercially available single-entity reference products (in agreement with modified dissolution rates), iii) superior benefit-risk ratio compared with reference products (suggested by preclinical synergistic antinociceptive effects, without potentiation of adverse effects), and iv) efficacy in a phase 2 trial of moderate to severe pain following extraction of ≥2 impacted third molars requiring bone removal, where CTC doses containing low doses of APIs exerted a significant effect. Phase 3 studies are currently ongoing.

Pharmacokinetics of Tramadol and Celecoxib in Japanese and Caucasian Subjects Following Administration of Co-Crystal of Tramadol-Celecoxib (CTC): A Randomised, Open-Label Study

BACKGROUND AND OBJECTIVES

Co-Crystal of Tramadol-Celecoxib (CTC) is a first-in-class active pharmaceutical ingredient (API-API) co-crystal of rac-tramadol.HCl and celecoxib in a 1:1 molecular ratio (100 mg CTC: 44 mg rac-tramadol.HCl and 56 mg celecoxib). Tramadol and celecoxib pharmacokinetics are modified after CTC administration versus administration of reference products. This randomised, open-label, crossover, phase 1 study assessed CTC pharmacokinetics, dose proportionality, safety and tolerability in Japanese and Caucasian subjects.

METHODS

CTC (100, 150 and 200 mg) was administered orally to healthy Japanese/Caucasian subjects. Tramadol, O-desmethyltramadol and celecoxib plasma concentrations were determined pre-dose and up to 48 h post-dose. Maximum observed plasma concentration (Cmax), and area under the plasma concentration-time curve from dosing to last measurable concentration (AUCt) and from dosing extrapolated to infinity (AUC∞) were evaluated. Dose proportionality was assessed in a dose-adjusted bioavailability analysis of variance and in a power model. Inter-cohort comparability of pharmacokinetic exposure was confirmed if the ratio (Japanese cohort/Caucasian cohort) of geometric least-squares means and corresponding 90% confidence intervals were 80-125%. Post hoc weight-adjusted comparability analyses were performed. Safety was assessed throughout.

RESULTS

Sixty subjects (21 males/9 females per cohort) were randomised; 57 completed the study. Cohorts were age and BMI matched; there were expected inter-cohort weight differences. Exposure to each analyte increased in both cohorts with increasing CTC dose. Tramadol's pharmacokinetic exposure was comparable between cohorts after adjusting for body weight; the pharmacokinetic exposure of O-desmethyltramadol and celecoxib was increased in Japanese subjects.

CONCLUSIONS

Differences in pharmacokinetics were not sufficient to suggest that CTC dose adjustment is required in Japanese subjects.

CLINICAL TRIAL REGISTRATION

EudraCT: 2015-003071-29.

The Effect of Food on Tramadol and Celecoxib Bioavailability Following Oral Administration of Co-Crystal of Tramadol-Celecoxib (CTC): A Randomised, Open-Label, Single-Dose, Crossover Study in Healthy Volunteers

BACKGROUND AND OBJECTIVE

Co-Crystal of Tramadol-Celecoxib (CTC), in development for the treatment of moderate to severe acute pain, is a first-in-class co-crystal containing a 1:1 molecular ratio of two active pharmaceutical ingredients; rac-tramadol·HCl and celecoxib. This randomised, open-label, crossover study compared the bioavailability of both components after CTC administration under fed and fasting conditions.

METHODS

Healthy adults received single doses of 200 mg CTC under both fed and fasting conditions (separated by a 7-day washout). Each dose of CTC was administered orally as two 100 mg tablets, each containing 44 mg tramadol·HCl and 56 mg celecoxib. In the fed condition, a high-fat, high-calorie meal [in line with recommendations by the US Food and Drug Administration (FDA)] was served 30 min before CTC administration. Tramadol, O-desmethyltramadol and celecoxib plasma concentrations were measured pre- and post-dose up to 48 h. Pharmacokinetic parameters were calculated using non-compartmental analysis. Safety was also assessed.

RESULTS

Thirty-six subjects (18 female/18 male) received one or both doses of CTC; 33 provided evaluable pharmacokinetic data under fed and fasting conditions. For tramadol and O-desmethyltramadol, fed-to-fasting ratios of geometric least-squares means and corresponding 90% confidence interval (CI) values for maximum plasma concentration (Cmax) and extrapolated area under the plasma concentration-time curve to infinity (AUC∞) were within the pre-defined range for comparative bioavailability (80-125%). For celecoxib, Cmax and AUC∞ fed-to-fasting ratios (90% CIs) were outside this range, at 130.91% (116.98-146.49) and 129.34% (121.78-137.38), respectively. The safety profile of CTC was similar in fed and fasting conditions.

CONCLUSIONS

As reported for standard-formulation celecoxib, food increased the bioavailability of celecoxib from single-dose CTC. Food had no effect on tramadol or O-desmethyltramadol bioavailability.

CLINICAL TRIAL REGISTRATION NUMBER

152052 (registered with the Therapeutic Products Directorate of Health Canada).

21st century developments in the understanding and control of molecular solids

This highlight article surveys some of the key recent advances in crystallization techniques, polymorphism, co-crystals, amorphous materials and crystal engineering.