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fentanyl citrate (OX20 / Rapinyl / EN 3267)

✓ Approved

Kyowa Kirin Co., Ltd. · Small Molecule · Small Molecule

What is fentanyl citrate?

fentanyl citrate is a small molecule developed by Kyowa Kirin Co., Ltd.. It is approved for therapeutic indications via oral (po) or sublingual (sl)/oral transmucosal or topical.

Drug Profile

Brand NamesOX20, Rapinyl, EN 3267
CompanyKyowa Kirin Co., Ltd.
Drug ClassSmall Molecule
RouteOral (PO), Sublingual (SL)/Oral Transmucosal, Topical
StatusApproved
Sources: ClinicalTrials.gov, Kyowa Kirin Co., Ltd.

Therapeutic Indications

fentanyl citrate is developed for 1 unique indication across 1 therapeutic area.

Therapeutic AreaConditionPhase
Neoplasms benign, malignant and unspecified (incl cysts and polyps)Cancer pain✓ Approved

Related Research Articles

PubMedCurrent opinion in critical care2026-09-18

Monitoring and dose adjustment of regional citrate anticoagulation for continuous renal replacement therapy.

Yessayan Lenar L, Szamosfalvi Balazs B, Tolwani Ashita A

Regional citrate anticoagulation (RCA) is the preferred anticoagulation strategy for many patients receiving continuous renal replacement therapy (CRRT). Safe implementation requires a coordinated prescription integrating citrate delivery, citrate removal within the extracorporeal circuit, individualized calcium replacement, CRRT fluid composition, and structured biochemical monitoring. This review summarizes practical approaches to RCA prescription, monitoring, and dose adjustment, emphasizing recent advances in citrate kinetics, calcium homeostasis, impaired citrate metabolism, metabolic complications, and systems-based safety. Randomized trials and meta-analyses continue to demonstrate that RCA prolongs circuit life and reduces bleeding compared with systemic heparin anticoagulation, although a mortality benefit has not been demonstrated. Recent studies have refined understanding of citrate dose, systemic citrate load, first-pass citrate extraction, individualized calcium replacement based on anticipated effluent calcium losses, and recognition of impaired citrate metabolism. They also support baseline ionized calcium assessment before CRRT initiation, integration of lactate trends into assessment of citrate metabolism, individualized CRRT fluid selection, and distinguishing true citrate accumulation from other metabolic effects of RCA. RCA is most effectively managed as an integrated CRRT prescription in which citrate delivery and removal, individualized calcium replacement, CRRT fluid composition, and operational parameters are coordinated to optimize circuit anticoagulation while maintaining electrolyte and acid-base homeostasis. Prescription adjustment should focus on four recurring clinical scenarios: inadequate circuit anticoagulation, negative calcium balance, excessive bicarbonate generation from citrate metabolism, and impaired citrate metabolism. Standardized protocols, structured monitoring, staff training, and workflow integration remain central to safe RCA implementation.

PMID 42758964
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PubMedProgress in transplantation (Aliso Viejo, Calif.)2026-09-18

Association Between Early Perioperative Fentanyl Exposure and Dose-Normalized Tacrolimus Exposure After Kidney Transplantation.

Abe Yohei Y, Kato Takuma T, Kaji Asuka A, Harada Satoshi S et al.

IntroductionTacrolimus exposure varies early after kidney transplantation, and perioperative factors may complicate therapeutic drug monitoring. Fentanyl is commonly used perioperatively, but its association with dose-normalized tacrolimus exposure is unclear. Project Aims or Questions: This study evaluated whether early perioperative fentanyl exposure was associated with dose-normalized tacrolimus exposure during the first week after kidney transplantation.DesignThis single-center retrospective program evaluation included 43 adult living-donor kidney transplant recipients who received perioperative fentanyl and had evaluable tacrolimus trough concentrations and corresponding oral daily doses. Cumulative fentanyl dose was the conventional exposure measure; body surface area-normalized and patient-controlled analgesia-administered volume measures were exploratory. The outcome was the log-transformed tacrolimus trough concentration divided by the daily tacrolimus dose. Repeated measurements were analyzed using linear mixed models adjusted for clinical covariates.ResultsThe conventional cumulative fentanyl dose through postoperative day 1 was associated with 22.7% higher dose-normalized tacrolimus exposure per 1 standard deviation increase, 95% confidence interval 4.4% to 44.1%, P = .013. In exploratory analyses, body surface area-normalized cumulative exposure through postoperative day 1 had the strongest association, a 24.9% increase, 95% confidence interval 7.3% to 45.4%, P = .004. Exposure through postoperative day 2 showed weaker, nonsignificant associations.ConclusionEarly perioperative fentanyl exposure, particularly cumulative exposure through postoperative day 1, was associated with higher dose-normalized tacrolimus exposure during the first postoperative week after kidney transplantation. These findings support contextual interpretation of early tacrolimus monitoring while recognizing confounding by clinical status and the exploratory nature of body surface area-normalized findings.

PMID 42757759
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PubMedHeart & lung : the journal of critical care2026-09-18

Comparison of analgesic efficacy of dexamethasone and dexmedetomidine as an adjuvant to local anaesthetic in transversus thoracic muscle plane block in adult patients undergoing median sternotomy: A randomised controlled trial.

Kumari Poonam P, Jha Lalit L, Kumar Amarjeet A, Sinha Chandni C et al.

Post-sternotomy pain contributes significantly to delayed recovery following cardiac surgery. The transversus thoracic muscle plane block (TTPB) is a recently described regional anaesthetic technique that provides analgesia to the anterior chest wall. The addition of adjuvants such as dexamethasone and dexmedetomidine may enhance the analgesic efficacy of TTPB. This study compared the analgesic efficacy of dexamethasone and dexmedetomidine as adjuvants to bupivacaine for TTPB in patients undergoing median sternotomy. 66 adult patients (ASA I-III) scheduled for cardiac surgery via median sternotomy were recruited for this randomised trial. Following induction of anaesthesia, all patients received bilateral TTPB and were allocated to three groups: dexamethasone (0.25 % bupivacaine + 8 mg dexamethasone), dexmedetomidine (0.25 % bupivacaine + 1 µg/kg dexmedetomidine), and a control group (0.25 % bupivacaine alone). The primary outcome was the time to first rescue analgesia following extubation. Secondary outcomes included 24-hour postoperative fentanyl consumption, intraoperative fentanyl requirement, pain scores, extubation time, patient satisfaction, and adverse events. Time to first rescue analgesia was significantly longer in the dexmedetomidine group than in the dexamethasone and control groups (P 0.001). Twenty-four-hour postoperative fentanyl consumption was significantly lower in both adjuvant groups than in the control group (P < 0.001). Pain scores were consistently lower with dexmedetomidine and dexamethasone groups. Extubation time and intraoperative fentanyl consumption were comparable among the three groups (P > 0.05). Both dexamethasone and dexmedetomidine improved TTPB analgesia. Dexmedetomidine significantly prolonged the duration of analgesia, whereas 24-hour postoperative opioid consumption was comparable between the adjuvant groups.

PMID 42759104
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PubMedInternational journal of biological macromolecules2026-09-18

Electrospun Zein/hydroxypropyl methylcellulose/silver citrate nanofibres with enhanced thermal and morphological stability for wound healing.

Aguila Marco Antonio Lopez MAL, Jia Jiaojiao J, Xu Yingde Y, Liang Yanqin Y et al.

Wound dressing is a critical in wound healing, yet natural electrospun nanofibres often lack thermal and morphological stability, limiting clinical utility. To address this, Zein nanofibrous mats with silver citrate nanorods (AgCit) were fabricated by electrospinning, crosslinked with citric acid (catalysed by sodium hypophosphite), and reinforced with hydroxypropyl methylcellulose (HPMC). FE-SEM revealed bead-free fibres at 5 mM AgCit, 40 wt% Zein, and 0.5 wt% HPMC, with an average diameter of 930 ± 5.5 nm. Morphological stability was achieved by HPMC reinforcement and AgCit, which prevent fibre collapse under aqueous immersion, while crosslinking was insufficient. Thermal stability was enhanced by citrate-Zein interactions and compact chain packing induced by HPMC, as confirmed by DSC (Tg1 above 100 °C) and TGA (reduced degradation rates). These strategies provided dual advantages: resilience under physiological conditions and improved durability during processing. Cell assays demonstrated cytocompatibility, proliferation, and migration, with AgCit supporting wound closure. Time-kill curves showed a 90.67 ± 0.49% and 92 ± 0.96% of antibacterial efficiency against E. coli and S. aureus, respectively within 9 h. The mechanism involves hydrogen bonding and chain entanglement between Zein and HPMC, reinforced by citrate crosslinking, while AgCit contributes antibacterial activity and HPMC provides antioxidant effect.

PMID 42759633
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PubMedSe pu = Chinese journal of chromatography2026-09-18

[Determination of 15 fentanyl analogs and amphetamine-type stimulants in hair by liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry].

Wei Qi Q, Su Fu-Hai FH, Zhu Xin X

Drug abuse is a major global public health problem. Fentanyl analogs and amphetamine-type stimulants （ATS） are widely abused worldwide. Hair analysis can trace drug use history over months. This technique has unique advantages in forensic toxicology. However， its application is limited by a lack of matrix-certified reference materials （CRMs）. At present， the existing CRMs are unable to simultaneously cover both fentanyl analogs and amphetamine-type stimulants. This study established a hair sample preparation method based on a water‑dimethyl sulfoxide‑hydrochloric acid soaking approach， targeting 15 analytes （nine fentanyl analogs and six ATS）. The soaking time was systematically investigated. Drug incorporation into hair reached a maximum at 24 days. A slight decrease was observed at 25 days. This decrease may result from desorption and solvent-induced structural changes in keratin. Therefore， 24 days was selected as the optimal soaking time. Preparation experiments demonstrated that 14 of the 15 drugs were successfully embedded into the hair matrix. This study also applied a dual-platform quantitative strategy for certification. The two platforms were liquid chromatography-tandem mass spectrometry （LC-MS/MS） and gas chromatography-mass spectrometry （GC-MS）. Cross-validation between the two platforms improved the reliability of certified values. Sample pretreatment conditions were optimized using Box-Behnken response surface methodology. Four factors were investigated： extraction temperature， extraction time， liquid-to-solid ratio， and hydrochloric acid concentration. The effects of the four factors on extraction efficiency followed a decreasing order： extraction temperature>extraction time>liquid-to-solid ratio>hydrochloric acid concentration. The optimal extraction conditions were as follows： extraction temperature 40 ℃， extraction time 50 min， liquid-solid ratio 100∶1 （mL/g）， and hydrochloric acid concentration 0.01 mol/L. Method validation was performed according to international guidelines. For LC-MS/MS， the limits of detection （LODs） and quantification （LOQs） were 0.05 pg/mg and 0.25 pg/mg， respectively. For GC-MS， the LODs and LOQs were 0.02 ng/mg and 0.08 ng/mg， respectively. Good linearities were obtained for all 15 drugs. Correlation coefficients （r） were greater than 0.999 for both platforms. Good linearities were obtained for all 15 analytes on both platforms with correlation coefficients >0.999 over the respective concentration ranges Intra-day precisions （n=6） were evaluated as relative standard deviations （RSDs）. Inter-day precision （n=30 over 5 days） was also calculated. For 14 drugs （except amphetamine）， RSD values ranged from 0.2% to 9.4%. All RSDs were below 10%， indicating good repeatability and intermediate precision. Stability of hair extracts was assessed at 1， 24， 48， 72， and 96 h at room temperature. The extracts were stable for at least 96 h when stored at room temperature， with RSDs below 6.0% for LC-MS/MS and below 10% for GC-MS. Recovery tests were performed at three quality control levels （low， medium， high）. For LC-MS/MS， average recoveries ranged from 84.46% to 116.4% （n=3）. For GC-MS， average recoveries ranged from 85.50% to 116.4% （n=3）. All RSDs were below 15%. Matrix effects （MEs） were evaluated by comparing matrix-matched standards with solvent standards. ME values between 80% and 120% （n=3） were observed for both platforms. These results indicate negligible ion suppression or enhancement. Homogeneity of the prepared hair reference material was assessed. The results show that the uniformity of the hair samples is good. The contents of the 14 drugs in the prepared hair samples were determined. For LC-MS/MS， the values ranged from 1.012 ng/mg to 7.830 ng/mg. For GC-MS， the values ranged from 1.087 ng/mg to 7.712 ng/mg. Amphetamine was not detected by either platform， likely due to its high polarity and weak binding to keratin. Most drugs showed good agreement between the two platforms. Relative deviations were below 10% for most analytes. However， methamphetamine showed a deviation of -12%. This may be due to matrix effects in LC-MS/MS. The GC-MS results for methamphetamine were more robust. The dual-platform approach allowed cross-validation and enhanced the reliability of the certified values. In conclusion， a dual-platform method based on LC-MS/MS and GC-MS was successfully applied to certify a new hair matrix reference material. The cross-validation strategy enhances the accuracy and traceability of the certified values. This work provides a valuable tool for quality control in forensic toxicology laboratories. The prepared reference material and validated method will facilitate inter-laboratory comparisons. They will also support the monitoring of drug abuse in forensic and clinical settings.

PMID 42754941
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PubMedMolecular pharmacology2026-09-18

High potency μ-opioid receptor agonists engage sodium-bound receptor states.

Powell Alexander J AJ, Griggs Nicholas W NW, Iñiguez-Lluhí Jorge A JA, Mosberg Henry I HI et al.

The simple 2-state conformational selection model of G protein-coupled receptor activation suggests that, by binding to a high-affinity state, an agonist shifts receptor equilibrium in favor of active state (R∗) conformations that recruit heterotrimeric G proteins over inactive (R) conformations. Agonist binding affinity at the μ-opioid receptor is reduced in the presence of Na+ ions, which stabilize R conformations. The binding of higher efficacy opioid agonists, such as [D-Ala2, NMe-Phe4, Gly-ol5]-enkephalin and fentanyl, is more sensitive to Na+ ions than lower efficacy ligands. However, the binding of the highly potent agonists etorphine and dihydroetorphine is less sensitive to Na+ ions than expected, such that the prevailing models fail to explain their pharmacology. To understand this discrepancy, experiments were performed to evaluate the binding properties and G protein activation of several high-affinity, high-potency agonists, including carfentanil, etonitazene, and several peptidomimetics in comparison to [D-Ala2, NMe-Phe4, Gly-ol5]-enkephalin, Met-enkephalin, fentanyl, and morphine in the presence of Na+ or K+ ions. Several very potent agonists retained high-affinity and potency in both ionic conditions, whereas the standard agonists displayed enhanced binding and signaling only in the presence of K+ ions. Comparison of the difference in binding affinity with degree of agonism afforded a negative correlation in which several ligands with a very high degree of agonism were least sensitive to Na+ ions. These data suggest that select highly potent μ-opioid receptor agonists have high-affinity for Na+ bound receptor states and shift the receptors into active conformations that efficiently couple to G protein. SIGNIFICANCE STATEMENT: The theory of conformational selection suggests that agonists bind to active states (R∗) of G protein-coupled receptors, including the μ-opioid receptor, to shift the receptor equilibrium in favor of R∗ over inactive states (R). This study demonstrates that ligands with very high-affinity and potency at the μ-opioid receptor can engage low-affinity Na+-bound receptor states (R) and convert these to active R∗ states that efficiently couple to G protein, suggesting a conformational induction model.

PMID 42759296
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