A Continuous Intestinal Absorption Model to Predict Drug Enterohepatic Recirculation in Healthy Humans: Nalbuphine as a Model Substrate.

Nalbuphine (NAL) is a κ-agonist/µ-antagonist opioid being developed as an oral extended formulation (ER) for the treatment of chronic cough in idiopathic pulmonary fibrosis and itch in prurigo nodularis. NAL is extensively glucuronidated and likely undergoes enterohepatic recirculation (EHR). The purpose of this work is to develop pharmacokinetic models for NAL absorption and enterohepatic recirculation (EHR). Clinical pharmacokinetic (PK) data sets in healthy subjects from three trials that included IV, oral solution, and ER tablets in fed and fasted state and two published trials were used to parametrize a novel partial differential equation (PDE)-based model, termed "PDE-EHR" model. Experimental inputs included in vitro dissolution and permeability data. The model incorporates a continuous intestinal absorption framework, explicit liver and gall bladder compartments, and compartments for systemic drug disposition. The model was fully PDE-based with well-stirred compartments achieved by rapid diffusion. The PDE-EHR model accurately reproduces NAL concentration-time profiles for all clinical data sets. NAL disposition simulations required inclusion of both parent and glucuronide recirculation. Inclusion of intestinal P-glycoprotein efflux in the simulations suggests that NAL is not expected to be a victim or perpetrator of P-glycoprotein-mediated drug interactions. The PDE-EHR model is a novel tool to predict EHR and food/formulation effects on drug PK. The results strongly suggest that even intravenous dosing studies be conducted in fasted subjects when EHR is suspected. The modeling effort is expected to aid in improved prediction of dosing regimens and drug disposition in patient populations.

A randomized, double-blind study to compare the efficacy and safety of nalbuphine nasal spray and injectable solution in patients after orthopaedic interventions and traumatological procedures.

AIMS: Our previous 3-period crossover study in healthy volunteers comparing the pharmacokinetics of nalbuphine nasal spray Apain with parenteral nalbuphine solution demonstrated high bioavailability of the nasal spray and close similarity of pharmacokinetic profiles after intranasal and intramuscular administration, especially within 30 min postdose. The aim of the present study was a noninferiority assessment of nalbuphine nasal spray vs. intramuscular injection for pain relief in postoperative patients. METHODS: Ninety orthopaedic and traumatology patients were enrolled in this double-blind, randomized study of the effectiveness and tolerance of a single 10.5 mg dose of nalbuphine nasal spray vs. 10 mg intramuscular injection. The summed pain intensity difference (SPID0-6) calculated using visual analogue scale scores was the primary study endpoint. RESULTS: Of 90 subjects enrolled, the per-protocol efficacy population comprised 79 patients; 6 patients in the reference group and 5 patients in the test group were excluded due to remedication. The mean values of study endpoints with 95% confidence interval were as follows in reference and test groups, respectively: SPID0-6 = 228.08 (205.73-250.43) vs. 248.73 9 (225.83-271.63), time to pain relief onset = 0.28 h (0.25-0.31) vs. 0.27 h (0.25-0.29), duration of analgesia = 5.55 h (5.17-5.93) vs. 5.51 h (5.10-5.92), area under the curve = 119.30 (91.17-147.43) vs. 99.81 (74.52-107.10). No statistically significant differences were revealed. CONCLUSION: Nalbuphine nasal spray Apain has been proven to be a safe, noninvasive alternative to intramuscular nalbuphine to relieve severe postoperative pain. Designed for self-administration and dose-adjusting, the noncontrolled opioid analgesic nalbuphine spray can be used for patient-controlled analgesia in out-of-hospital, field and home settings.

Breast Milk Excretion of Dinalbuphine Sebacate Injection Administered After Cesarean Section.

Ensuring the safety of analgesics during lactation is crucial for women of childbearing potential. Available data regarding the transfer of nalbuphine for postoperative acute pain via breast milk are limited to the postmarketing experience. This lactation study aimed to assess nalbuphine and dinalbuphine sebacate concentrations in breast milk from lactating women with postoperative pain treated with dinalbuphine sebacate extended-release injection (150 mg dinalbuphine sebacate/2 mL Naldebain). Breast milk was collected throughout the 5-day posthospitalization interval from 20 mothers injected with one dose of extended-release dinalbuphine sebacate intramuscularly. Maternal safety was assessed during the study period. Nalbuphine was detectable in 71% of milk samples collected from all mothers, whereas dinalbuphine sebacate was undetectable or below the quantitation limit (0.1 ng/mL). The mean nalbuphine concentration in milk was approximately 10.55 ng/mL, with the peak concentration reaching up to 12.7 ng/mL. The mean relative infant dose was 0.39% (coefficient of variation, 65%). The mean pain intensity at rest was reduced to mild pain from Day 2 morning to discharge. Overall, the maternal safety profile was tolerable. The breast milk of women who receive one dose of dinalbuphine sebacate injection postpartum contains low nalbuphine concentration. In addition, dinalbuphine sebacate injection potentially reduces maternal pain intensity during the first postpartum week and offers low toxicity risk among breastfed infants.

Comparative pharmacokinetics of nalbuphine nasal spray and solution for injection in healthy volunteers.

AIMS: Nalbuphine is a synthetic opioid with comparable analgesic activity to morphine but with a better safety profile. Nalbuphine is only available in injectable form due to low oral bioavailability. Nasal nalbuphine spray provides advantages in drug safety, avoids hepatic first-pass metabolism, is non-invasive and is convenient for patient-controlled analgesia by self-administration. This study aimed to evaluate the safety and pharmacokinetics (PK) of the newly developed nalbuphine nasal spray in comparison with a solution for injections. METHODS: Twenty-four healthy Caucasian volunteers were enrolled in this randomized, open-label, cross-over study. Subjects were administered one of the drugs: nasal spray 7.0 mg/dose, nalbuphine hydrochloride solution for injection 10 mg/dose intravenously (IV) or intramuscularly (IM). High-performance liquid chromatography-tandem mass spectrometry was used to determine nalbuphine concentrations. RESULTS: A comparison of PK profiles for IV, IM and intranasal (IN) routes of nalbuphine administration revealed a close similarity of absorption phases for nasal spray and IM injection. Differences between the mean Tmax and dose-adjusted Cmax values for nasal spray and IM injection were statistically insignificant. The median values of the elimination rate constants and the terminal elimination half-life following IV, IM and IN nalbuphine administration were similar. The mean absolute bioavailability of the nasal spray equalled 65.04%. CONCLUSIONS: The similarity of PK parameters of IM-injected nalbuphine solution and the nasal spray allows us to assume the latter is a feasible alternative to intramuscular nalbuphine injections appropriate for self-administration and field environments for managing moderate and severe pain of various aetiologies.

A Validated UHPLC-MS/MS Method for Determination of Nalbuphine in Human Plasma and Application for Pharmacokinetic Study of Patients Undergoing General Anesthesia.

Nalbuphine was a semisynthetic opioid analgesic widely used in the treatment of both acute and chronic pain. We developed and validated a rapid, simple and sensitive method by ultra-performance liquid chromatography-tandem mass spectrometry (MS/MS) for the simultaneous quantitation of nalbuphine in human plasma, and we reported the pharmacokinetic features of patients during general anesthesia for abdominal surgery. Sample separation was achieved on a Kinetex Phenyl-Hexyl column (50 × 2.1 mm, 1.7 µm) after simple protein precipitation with acetonitrile. The mobile phase was composed of acetonitrile and 3 mM of ammonium acetate aqueous solution with 0.1% formic acid. Gradient elution was used in 4.5 min with a flow rate of 0.5 mL/min at 40°C. MS detection using AB Sciex QTRAP 5500 mass spectrometer was characterized by electrospray ionization for positive ions in multiple reaction monitoring mode. Quantitative ion pairs were m/z 358.4 â†’ 340.1 for nalbuphine and m/z 340.0 â†’ 268.3 for nalmefene, which were used as the internal standard (IS). The calibration curves showed good linearity (r2>0.99) over concentration range of 0.1-500 ng/mL. The intra-and inter-batch precisions were within 10.67%, and accuracy ranged from 94.07 to 105.34%. The IS-normalized matrix factors were 1.02-1.03 with RSD% (≤5.82%). The recoveries ranged from 101.09 to 106.30%. In conclusion, a rapid, simple, sensitive and economical analytical method was developed and validated to detect the concentration in plasma samples obtained from patients receiving nalbuphine intravenous injection and was successfully applicated to human pharmacokinetic studies of nalbuphine.

Pharmacokinetic Study of Nalbuphine in Surgical Patients Undergoing General Anesthesia with Varying Degrees of Liver Dysfunction.

Purpose: This study aimed to characterize the pharmacokinetics of nalbuphine in patients undergoing general anesthesia with varying degrees of liver dysfunction. Patients and Methods: Twenty-four patients were enrolled and divided into three cohorts based on liver function: normal liver function (n = 13), mild liver dysfunction (n = 5), and moderate/severe liver dysfunction (n = 6). During the induction of anesthesia, they received 15 mg of nalbuphine intravenously. Venous blood samples were collected from each patient. The plasma concentration of nalbuphine was determined using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The pharmacokinetic parameters of nalbuphine were calculated by non-compartmental analysis (NCA) using Phoenix WinNonlin software. Results: Compared with the normal liver function group, the plasma elimination half-life (T1/2) of nalbuphine was increased by approximately 33% in the moderate/severe liver dysfunction group (2.66 h vs 3.54 h, P<0.05), and the volume of distribution (Vd) increased by approximately 85% (100.08 L vs 184.95 L, P<0.05). Multivariate analysis revealed that weight and platelet were associated with clearance (CL); total bilirubin as an independent factor was associated with T1/2, and weight associated with area under the curve (AUC(0→∞)) independently. Conclusion: The T1/2, mean residence time, and Vd of nalbuphine in patients with moderate/severe liver dysfunction were prolonged or increased significantly compared with those in the normal liver function group. These data suggest that it may need to be used with caution when nalbuphine is administered to patients with moderate or severe liver dysfunction.

Pharmacokinetic comparison of nalbuphine with single injection and patient-controlled analgesia mimic method in healthy Chinese volunteers.

WHAT IS KNOWN AND OBJECTIVE: Nalbuphine is a mu (µ) receptor partial antagonist/kappa (κ) receptor agonist analgesic and can be administered as a single injection or using patient-controlled analgesia (PCA) in the clinical setting. However, differences in the pharmacokinetics of the two administration methods are unclear. Here, a clinical trial was performed to compare the pharmacokinetic characteristics and superiority of nalbuphine with a single-injection or PCA-mimic method to provide a reference for the selection of an appropriate administration method. METHODS: Twenty healthy individuals were divided into two groups and injected with 10 mg nalbuphine intravenously using a single-injection or a PCA-mimic method (2 mg once for five times with a 30-min interval). Blood samples were collected, and safety was investigated. The liquid chromatography-tandem mass spectrometry was adopted to determine the concentration of nalbuphine in plasma. RESULTS AND DISCUSSION: The maximum concentration (Cmax ) and area under concentration-time curve (AUC0-t ) values of nalbuphine in the single-injection and PCA groups were as follows: Cmax , 81.3 ± 24.7 and 39.8 ± 6.4 ng/ml, respectively; moreover, AUC0-t , 110.3 ± 19.5 and 128.3 ± 23.0 h ng/ml, respectively. The effective analgesic concentration durations (EACDs) for the two administration methods were 1.39 ± 0.64 and 1.96 ± 0.91 h, respectively. Nalbuphine was well tolerated, and improvements were observed in the PCA group. WHAT IS NEW AND CONCLUSION: Compared with those in the single-injection group, the AUC0-t and EACDs in the PCA group were similar, whereas Cmax was decreased significantly. Therefore, the PCA method was more suitable for the clinical application of nalbuphine injection owing to the superiority of lower concentration fluctuation and the improved safety profile.

A dual system platform for drug metabolism: Nalbuphine as a model compound.

Reaction phenotyping is a method commonly used for characterizing drug metabolism. It determines the drug metabolic pathways and ratios by measuring the metabolized fractions of individual enzymes. However, currently published results have focused on cytochrome P450s (CYPs), while not considering phase II metabolism. Therefore, the morphinan analgesic, nalbuphine, primarily metabolized in the liver via CYPs and UDP-glucuronosyltransferases (UGTs), was selected as a model drug to establish a dual-phase platform to elucidate its comprehensive metabolic pathway. Enzyme kinetics was studied using 8 common recombinant (r)CYPs, 10 rUGTs, and pooled human liver microsomes. The overall fraction of nalbuphine metabolized by each isozyme was evaluated by determining parent drug depletion. Finally, in vitro-in vivo correlation was validated in animal studies. Fluconazole, a specific UGT2B7 inhibitor, was administered orally to rats to determine the pharmacokinetic effects on nalbuphine and nalbuphine metabolites. Seventy-five percent and 25% of nalbuphine was metabolized by UGTs and CYPs, respectively. UGT2B7, UGT1A3, and UGT1A9 were primarily responsible for nalbuphine glucuronidation; only UGT2B7 produced nalbuphine-6-glucuronide. CYP2C9 and CYP2C19 were the two CYP isozymes that produced 3'-hydroxylnalbuphine and 4'-hydroxylnalbuphine. In vivo, the maximum serum concentration (Cmax) and area under the curve (AUC) of nalbuphine increased 12.4-fold and 13.2-fold, respectively, with fluconazole co-administration. A dual system platform for drug metabolism was successfully established in this study and was used to generate a complete metabolic scheme for nalbuphine. This platform has been verified by in vivo evaluations and can be utilized to study drugs that undergo multisystem metabolism.

Does nalbuphine have a niche in managing pain?

Nalbuphine has been commercially available for 40 years for the treatment of acute pain; few studies have centered on management of chronic pain. Nalbuphine unique pharmacology is an advantage in pain management. It is µ antagonist, partial κ agonist for G-proteins and beta-arrestin-2. Benefits are related to G-protein interactions resulting in less nausea, pruritus, and respiratory depression than morphine. At low doses, nalbuphine reduces side effects particularly respiratory depression without loss of analgesia when combined with potent opioids. Nalbuphine pharmacokinetics are moderately altered in renal failure. Several studies have found that nalbuphine reduces uremic pruritus. Nalbuphine has drawbacks: it is not an oral formulation, it causes withdrawal in patients on sustained released opioids, and it cannot be used to treat an opioid withdrawal syndrome. Nalbuphine, despite being a µ receptor antagonist produces a drug-liking effect and can be abused. There are very few deaths associated with nalbuphine alone in part due to the fact it is rarely used but also related to a ceiling on respiratory depression.

Tissue Residue Levels after Immobilization of Rocky Mountain Elk ( Cervus elaphus nelsoni) using a Combination of Nalbuphine, Medetomidine, and Azaperone Antagonized with Naltrexone, Atipamezole, and Tolazoline.

Previous studies demonstrated that nalbuphine, medetomidine, and azaperone (NalMed-A) can effectively immobilize adult elk ( Cervus elaphus nelsoni), and be antagonized using naltrexone and atipamezole, with or without tolazoline. To assess duration of tissue residues for this immobilization package, we immobilized 14 captive adult elk with NalMed-A, then euthanized animals and collected tissues 0, 3, 6, 14, 21, or 28 d later. Except for two animals euthanized immediately, all elk were recovered using naltrexone, atipamezole, and tolazoline. Tissue residues (≥0.01 parts per million) for the tranquilizers nalbuphine, medetomidine, and azaperone were detected in liver and muscle tissue samples from elk euthanized within 40 min postinjection (PI) and one animal that died 12-24 h PI, but not in tissues from any of the animals euthanized at 3, 6, 14, 21, or 28 d PI. Tissue residues for the antagonists naltrexone, atipamezole, and tolazoline were detected in liver and muscle of the animal that died 12-24 h PI. Only naltrexone was detected in liver from the two elk euthanized at day 3, and no antagonist residues were detected thereafter.

Pharmacokinetic Profiles of Nalbuphine after Intraperitoneal and Subcutaneous Administration to C57BL/6 Mice.

Mice undergo a variety of procedures that necessitate the use of analgesic agents. Opioids are often essential to successful pain management plans, but most are controlled substances, and their use requires appropriate federal and state registrations. Nalbuphine is a potentially effective opioid analgesic for mice that is not currently classified as a controlled substance. This compound has received little attention as an analgesic for mice, and standard dosage regimens have not been developed. Here we compared the pharmacokinetic profiles of 10 mg/kg nalbuphine in male C57BL/6 mice subcutaneous or intraperitoneal administration. Blood was collected from 3 mice per treatment at 5, 10, 20, and 30 min and 1, 2, 3, 6, 12, and 24 h after administration. Plasma concentrations were measured, and standard pharmacokinetic parameters were calculated. Profile characteristics for each route of administration were similar, with significant differences in plasma concentration at 5 and 30 min and 1 and 3 h. Nalbuphine was absorbed more quickly when administered subcutaneously (Tmax, 5 min) than intraperitoneally (Tmax, 10 min), whereas the drug's half-life was similar between the intraperitoneal (0.94 h) and subcutaneous (1.12 h) routes. The AUC0-tldc and AUC0-inf were higher but the apparent clearance and apparent volume of distribution were lower after subcutaneous administration compared with intraperitoneal dosing. Plasma concentrations were below the level of detection by 12 h. These results suggest that nalbuphine is absorbed in and eliminated quickly from mice, making it a possible candidate for acute pain management.

In vitro and in vivo release of dinalbuphine sebacate extended release formulation: Effect of the oil ratio on drug release.

Nalbuphine is a semi-synthetic opioid indicated for the relief of moderate to severe pain. Dinalbuphine sebacate (DNS) is a prodrug of nalbuphine for which we have developed long-acting lipophilic formulations in a benzyl benzoate/sesame oil mixture for intramuscular (IM) injection. In this study, we found that the in vitro release profile of DNS could be affected by adjusting the weight ratio of benzyl benzoate to sesame oil (the solvent/oil ratio). A longer release period could be attained by increasing the solvent/oil ratio in the formulation. A pharmacokinetic study was conducted in beagle dogs to verify the relationship between the in vitro release and the drug release from the formulations in vivo. The pharmacokinetic study confirmed that the formulation with a higher benzyl benzoate to oil ratio exhibits a longer drug release profile with a lower maximum concentration (Cmax) and a longer time to peak blood concentration level (Tmax) than the formulation with a lower benzyl benzoate to oil ratio.

Pharmacokinetics of dinalbuphine sebacate and nalbuphine in human after intramuscular injection of dinalbuphine sebacate in an extended-release formulation.

Nalbuphine is a semi-synthetic opioid indicated for the relief of moderate to severe pain. Its short half-life requires frequent injections in clinical practice, resulting in a greater incidence of adverse events. A prodrug of nalbuphine has been developed, dinalbuphine sebacate (DNS), dissolved in a simple oil-based injectable formulation, which could deliver and maintain an effective blood level of nalbuphine. An open-label, prospective, two-period study was performed in healthy volunteers to verify the extended blood concentration profile of nalbuphine. Twelve healthy Taiwanese were randomized to receive an intramuscular injection of 20 mg nalbuphine HCl and 150 mg DNS sequentially with a washout period of 5 days. To prevent DNS hydrolysis during sample analysis, the effect of four esterase inhibitors was evaluated in the quantitation of DNS in human whole blood and thenoyltrifluoroacetone was chosen. The bioavailability of nalbuphine from intramuscularly injected DNS relative to that from nalbuphine HCl was 85.4%. The mean absorption time of nalbuphine from DNS was 145.2 h. It took approximately 6 days for the complete release of DNS into the blood stream where DNS was rapidly hydrolysed to nalbuphine; suggesting a single injection of 150 mg DNS in our extended-release formulation could provide long-lasting pain relief.

Pharmacokinetics of nalbuphine hydrochloride extended release tablets in hemodialysis patients with exploratory effect on pruritus.

BACKGROUND: Uremic pruritus is a common and deleterious condition among hemodialysis (HD) patients. Central gating of µ/κ opiate circuitry plays an important role in mediating and countering pruritogenic sensation. The objective of this study was to assess the safety and pharmacokinetics (PK) of the mixed µ-antagonist/κ-agonist nalbuphine, administered orally as nalbuphine HCl extended release (ER) tablets in HD patients, and explore its effect on pruritus. METHODS: In this open-label multiple escalating dose study, 15 HD patients with pruritus and 9 matched healthy subjects were enrolled. Nalbuphine HCl ER dose was escalated from 30 mg QD to 240 mg BID over 15 days. A full PK profile was obtained under dialysis and non-dialysis conditions as a function of dose. Clearance during dialysis was determined by sampling dialysate and arterial/venous blood during dialysis. Pruritus severity was assessed twice daily using a Visual Analog Scale (VAS). Safety monitoring included extensive monitoring of EKG, blood pressure, and pulse oximetry. RESULTS: In HD patients, nalbuphine concentration peaked within 4-9 hours and attained steady state within 2-3 days, with no significant accumulation. Mean half-life was 14.2 hours, mean Cmax and AUCtau ranged between 13 and 83 ng/mL and 118 and 761 ng∙h/mL, respectively, with exposure increasing in a nearly dose-proportional fashion. Exposure in HD patients was about 2-fold higher than in healthy subjects. There was no meaningful difference between exposure on dialysis and non-dialysis days with 1% or less of the dose removed by dialysis. Nalbuphine suppressed itch in a dose-dependent manner, reducing mean VAS score from 4.0 to 1.2 at 180 mg and 0.4 at 240 mg. CONCLUSIONS: Nalbuphine HCl ER tablets can be safely administered to HD patients without dose adjustment up to 240 mg BID and may hold promise in treating uremic pruritus.

[Nalbuphine in pediatric anesthesia]. / Nalbuphin in der Kinderanästhesie.

Efficient and safe pediatric perioperative pain therapy in the context of a multimodal pain therapy concept requires a slight to moderate opioid analgesic. Nalbuphine is a nearly ideal opioid for this purpose due to its unique pharmacological properties as a µ-receptor antagonist/κ-receptor agonist and a high safety profile. Nalbuphine is used clinically primarily in postoperative pain therapy administered as a bolus, continuous infusion and patient-controlled analgesia. Furthermore, it is administered in different regimens for pediatric diagnostic and interventional sedation.

Pharmacokinetics and effect of intravenous nalbuphine in weaned Holstein calves after surgical castration.

The objective of this study was to investigate the pharmacokinetics and effect of nalbuphine administered intravenously to calves immediately prior to surgical castration. Ten healthy calves were randomly assigned to two treatments (n = 5): (i) 0.9% sodium chloride (CONT) placebo, (ii) nalbuphine hydrochloride (NAL) (0.4 mg/kg). Blood samples collected over 10 h postcastration were analyzed for nalbuphine and cortisol concentrations. Additionally, heart rate, respiratory rate, rectal temperature, and step count was compared between groups using a random-effects mixed model. Changes in behavior and attitude were assessed using a six-point ordinal scoring system and compared using chi-square analysis. Plasma NAL concentrations were only detectable for 3 h postadministration (T½ = 0.68 h; Range: 0.53-0.79 h). There was no effect of NAL treatment prior to castration on cortisol concentrations (P = 0.99), heart rate (P = 0.73), respiratory rate (P = 0.59), rectal temperature (P = 0.22), and step count (P = 0.08) but fewer calves showed signs of head shaking, kicking, and tail flicking in the NAL group compared with the CONT group (P = 0.036). Therefore, we conclude that a single intravenous injection of nalbuphine at 0.4 mg/kg reduced some pain-related behaviors but did not significantly eliminate the physiological signs of distress in calves after surgical castration.

Simultaneous determination of nalbuphine and its prodrug sebacoly dinalbuphine ester in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry and its application to pharmacokinetic study in humans.

A rapid, simple, sensitive and selective ultraperformance liquid chromatography-tandem spectrometry (UPLC-MS/MS) method for the determination of nalbuphine and its prodrug sebacoly dinalbuphine ester (SDE) was developed and validated in human plasma. The sample pretreatment involves basification and iterative liquid-liquid extraction with ethyl-ether-dichloromethane (7:3, v/v) solution, followed by LC separation and positive electrospray ionization (ESI) API-3000 mass spectrometry detection. The chromatography was on a Waters Acquity UPLC BEH HILIC column (2.1 × 100 mm, 1.7 µm). The mobile phase was composed of acetonitrile and water (83:17, v/v) that contained 0.2% formic acid and 4 mm ammonium formate at a flow rate of 0.25 mL/min. Ethylmorphine and naloxine were selected as the SDE and nalbuphine internal standard (IS), respectively. The calibration curve for both was linear over the range from 0.05 to 20 ng/mL, with correlation coefficients ≥0.995. The lower limit of quantification was set at 0.05 ng/mL. The intra- and inter-day precision values for nalbuphine and SDE were acceptable as per FDA guidelines. The method was applied successfully to determine nalbuphine concentration in human plasma samples obtained from four Taiwanese volunteers receiving intramuscularly administration of sebacoyl dinalbuphine ester. The method is sensitive, selective and directly applicable to human pharmacokinetic studies involving nalbuphine.

Pharmacokinetics of long-acting nalbuphine decanoate after intramuscular administration to Hispaniolan Amazon parrots (Amazona ventralis).

OBJECTIVE: To evaluate the pharmacokinetics of nalbuphine decanoate after IM administration to Hispaniolan Amazon parrots (Amazona ventralis). ANIMALS: 9 healthy adult Hispaniolan Amazon parrots of unknown sex. PROCEDURES: Nalbuphine decanoate (37.5 mg/kg) was administered IM to all birds. Plasma samples were obtained from blood collected before (time 0) and 0.25, 1, 2, 3, 6, 12, 24, 48, and 96 hours after drug administration. Plasma samples were used for measurement of nalbuphine concentrations via liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were estimated with computer software. RESULTS: Plasma concentrations of nalbuphine increased rapidly after IM administration, with a mean concentration of 46.1 ng/mL at 0.25 hours after administration. Plasma concentrations of nalbuphine remained > 20 ng/mL for at least 24 hours in all birds. The maximum plasma concentration was 109.4 ng/mL at 2.15 hours. The mean terminal half-life was 20.4 hours. CONCLUSIONS AND CLINICAL RELEVANCE: In Hispaniolan Amazon parrots, plasma concentrations of nalbuphine were prolonged after IM administration of nalbuphine decanoate, compared with previously reported results after administration of nalbuphine hydrochloride. Plasma concentrations that could be associated with antinociception were maintained for 24 hours after IM administration of 37.5 mg of nalbuphine decanoate/kg. Safety and analgesic efficacy of nalbuphine treatments in this species require further investigation to determine the potential for clinical use in pain management in psittacine species.

Antinociceptive effects of long-acting nalbuphine decanoate after intramuscular administration to Hispaniolan Amazon parrots (Amazona ventralis).

OBJECTIVE: To evaluate the thermal antinociceptive effects and duration of action of nalbuphine decanoate after IM administration to Hispaniolan Amazon parrots (Amazona ventralis). ANIMALS: 10 healthy adult Hispaniolan Amazon parrots of unknown sex. PROCEDURES: Nalbuphine decanoate (33.7 mg/kg) or saline (0.9% NaCl) solution was administered IM in a randomized complete crossover experimental design (periods 1 and 2). Foot withdrawal threshold to a noxious thermal stimulus was used to evaluate responses. Baseline thermal withdrawal threshold was recorded 1 hour before drug or saline solution administration, and thermal foot withdrawal threshold measurements were repeated 1, 2, 3, 6, 12, 24, 48, and 72 hours after drug administration. RESULTS: Nalbuphine decanoate administered IM at a dose of 33.7 mg/kg significantly increased thermal foot withdrawal threshold, compared with results after administration of saline solution during period 2, and also caused a significant change in withdrawal threshold for up to 12 hours, compared with baseline values. CONCLUSIONS AND CLINICAL RELEVANCE: Nalbuphine decanoate increased the foot withdrawal threshold to a noxious thermal stimulus in Hispaniolan Amazon parrots for up to 12 hours and provided a longer duration of action than has been reported for other nalbuphine formulations. Further studies with other types of nociceptive stimulation, dosages, and dosing intervals as well as clinical trials are needed to fully evaluate the analgesic effects of nalbuphine decanoate in psittacine birds.

Pharmacokinetics of nalbuphine hydrochloride after intravenous and intramuscular administration to Hispaniolan Amazon parrots (Amazona ventralis).

OBJECTIVE: To assess the pharmacokinetics of nalbuphine HCl after IV and IM administration to Hispaniolan Amazon parrots (Amazona ventralis). ANIMALS: 8 healthy adult Hispaniolan Amazon parrots of unknown sex. PROCEDURES: Nalbuphine HCl (12.5 mg/kg) was administered IV and IM to all birds in a complete randomized crossover study design; there was a washout period of 21 days between subsequent administrations. Plasma samples were obtained from blood collected at predetermined time points for measurement of nalbuphine concentration by use of liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were estimated by use of computer software. RESULTS: Nalbuphine was rapidly eliminated with a terminal half-life of 0.33 hours and clearance of 69.95 mL/min/kg after IV administration and a half-life of 0.35 hours after IM administration. Volume of distribution was 2.01 L/kg after IV administration. The fraction of the dose absorbed was high (1.03) after IM administration. No adverse effects were detected in the parrots during the study. CONCLUSIONS AND CLINICAL RELEVANCE: In Hispaniolan Amazon parrots, nalbuphine appeared to have good bioavailability after IM administration and was rapidly cleared after IV and IM administration. Safety and analgesic efficacy of various nalbuphine treatment regimens in this species require further investigation to determine the potential for clinical palliation of signs of pain in psittacine species.