Pharmacokinetics of hydromorphone after intravenous, peroral and rectal administration to human subjects

Current Updates in Rectal Infusion of Fluids and Medications

Purpose of Review

Rectal infusion is a feasible alternative for the immediate administration of medication and fluids when intravenous access is delayed, contraindicated, or unnecessary. Advances in medical device technology have made rectal infusion more practical and easier for medical care providers, and more comfortable for patients. This paper briefly reviews the history of therapeutic rectal infusion, including recent improvements in technology and the existing evidence for the use of this technique.

Recent Findings

While ultrasound-guided peripheral intravenous (PIV) access techniques and other alternatives to landmark-based PIV catheter insertion have recently improved the ability of providers to overcome challenges related to difficult vascular access (DVA), these challenges are increasingly affecting patient outcomes, emergency department throughput, and the cost of medical care. In recent years, waves of parenteral drug, fluid, and supply shortages have affected hospitals. Concurrently, advances in rectal infusion technology have made rectal infusion easier, more comfortable, and more cost-effective than many parenteral options.

Summary

The infusion of resuscitative fluids and medications via the rectal route has previously fallen out of favor due to concurrent improvements in IV access devices. However, this technique demonstrates the potential for a reemergence considering the current challenges facing healthcare providers and systems. Improvements in rectal infusion devices, coupled with an aging population, increased incidence of DVA, shortages in parenteral drugs, fluids, supplies and skilled staff, and the need for care improvements in the post-acute setting have contributed to a greater need for easy, safe and effective alternatives to IV infusion.

Intravenous Patient-Controlled Analgesia Versus Oral Opioid to Maintain Analgesia for Severe Cancer Pain: A Randomized Phase II Trial

BACKGROUND

Optimal analgesic maintenance for severe cancer pain is unknown. This study evaluated the efficacy and safety of intravenous patient-controlled analgesia (IPCA) with continuous infusion plus rescue dose or bolus-only dose versus conventional oral extended-release morphine as a background dose with normal-release morphine as a rescue dose to maintain analgesia in patients with severe cancer pain after successful opioid titration.

METHODS

Patients with persistent severe cancer pain (≥7 at rest on the 11-point numeric rating scale [NRS]) were randomly assigned to 1 of 3 treatment arms: (A1) IPCA hydromorphone with bolus-only dose where dosage was 10% to 20% of the total equianalgesic over the previous 24 hours (TEOP24H) administered as needed, (A2) IPCA hydromorphone with continuous infusion where dose per hour was the TEOP24H divided by 24 and bolus dosage for breakthrough pain was 10% to 20% of the TEOP24H, and (B) oral extended-release morphine based on TEOP24H/2 × 75% (because of incomplete cross-tolerance) every 12 hours plus normal-release morphine based on TEOP24H × 10% to 20% for breakthrough pain. After randomization, patients underwent IPCA hydromorphone titration for 24 hours to achieve pain control before beginning their assigned treatment. The primary endpoint was NRS over days 1 to 3.

RESULTS

A total of 95 patients from 9 oncology study sites underwent randomization: 30 into arm A1, 32 into arm A2, and 33 into arm B. Arm B produced a significantly higher NRS over days 1 to 3 compared with arm A1 or A2 (P<.001). Daily NRS from day 1 to day 6 and patient satisfaction scores on day 3 and day 6 were worse in arm B. Median equivalent-morphine consumption increase was significantly lower in A1 (P=.024) among the 3 arms. No severe adverse event occurred in any arm.

CONCLUSIONS

Compared with oral morphine maintenance, IPCA hydromorphone for analgesia maintenance improves control of severe cancer pain after successful titration. Furthermore, IPCA hydromorphone without continuous infusion may consume less opioid.

Hydromorphone Prescription for Pain in Children-What Place in Clinical Practice?

While morphine is the gold standard treatment for severe nociceptive pain in children, hydromorphone is increasingly prescribed in this population. This review aims to assess available knowledge about hydromorphone and explore the evidence for its safe and effective prescription in children. Hydromorphone is an opioid analgesic similar to morphine structurally and in its pharmacokinetic and pharmacodynamic properties but 5-7 times more potent. Pediatric pharmacokinetic and pharmacodynamic data on hydromorphone are sorely lacking; they are non-existent in children younger than 6 months of age and for oral administration. The current data do not support any advantage of hydromorphone over morphine, both in terms of efficacy and safety in children. Morphine should remain the treatment of choice for moderate and severe nociceptive pain in children and hydromorphone should be reserved as alternative treatment. Because of the important difference in potency, all strategies should be taken to avoid inadvertent administration of hydromorphone when morphine is intended.

Hydromorphone population pharmacokinetics in pediatric surgical patients

BACKGROUND

Hydromorphone is an opioid agonist used for pediatric analgesia. Due to lack of data, pediatric dosing (based on adult pharmacokinetic models) is not optimal.

AIM

This study characterizes hydromorphone population pharmacokinetics in pediatric surgical patients.

METHODS

In this prospective observational study, 34 children (4-18 years, bodyweight 23-89.6 kg) received multiple intravenous hydromorphone boluses followed by postoperative hydromorphone patient-controlled analgesia. Arterial blood samples were collected before and at 3, 10, 30, and 90 (and few samples at 1350) minutes after the first dose. Hydromorphone concentrations were measured by validated LC-MS/MS assay. Nonlinear mixed-effects modeling was used for pharmacokinetic model development. The final population pharmacokinetic model was evaluated by visual predictive check and bootstrap analysis. Monte Carlo simulations based on the final pharmacokinetic model determined optimal patient-controlled analgesia parameters to achieve a target of 20 ng/mL (as the median effective analgesic concentration), using minimum effective analgesic concentration of 4 ng/mL as a proxy for patient-controlled analgesia dose demand, and not exceeding the defined safe upper threshold of 40 ng/mL.

RESULTS

Hydromorphone pharmacokinetic profiles were adequately described by a two-compartmental model with first-order elimination. Bodyweight was found to be a significant covariate for hydromorphone clearance. Allometrically scaledpharmacokinetic parameter estimates (per 70 kg), systemic clearance (0.748 L/min), volume of distribution (33 L), peripheral clearance (1.57 L/min), and peripheral volume of distribution (146 L) were similar to reported adult parameter estimates. Sex, race, age, and type of surgery were not identified as significant covariates. To identify optimal patient-controlled analgesia dosing parameters, we simulated several initial loading doses, demand doses, and lockout intervals. Our simulations support an initial patient-controlled analgesia loading dose of 15 µg/kg followed by a demand dose of 6 µg/kg with lockout intervals of 20 minutes.

CONCLUSIONS

After intravenous hydromorphone, plasma pharmacokinetic profiles in children undergoing different surgeries were well described by a two-compartment population allometric pharmacokinetic model using bodyweight as the size descriptor. Model informed simulations identified patient-controlled analgesia parameters to inform initial settings, with adjustments as needed based on observed individual effects.

Pharmacokinetics and Abuse Potential of Asalhydromorphone, a Novel Prodrug of Hydromorphone, After Intranasal Administration in Recreational Drug Users

OBJECTIVES

Hydromorphone (HM) is a potent μ-opioid receptor agonist with high susceptibility for abuse. A prodrug of hydromorphone, asalhydromorphone (ASAL-HM), has been designed to deter nonoral forms of abuse associated with hydromorphone. This study evaluated the intranasal (IN) pharmacokinetics and exploratory abuse potential of ASAL-HM compared with HM.

DESIGN

Single-center, randomized, double-blind, crossover study.

SETTING

Clinical research site.

SUBJECTS

Healthy adult, nondependent recreational opioid users.

METHODS

Subjects (N = 26) were randomized to receive IN administration of 16.1 mg of ASAL-HM and 8.0 mg of HM (molar-equivalent with respect to hydromorphone). Blood samples were taken through 24 hours postdose, and pharmacodynamic end points (Drug Liking, Feeling High, Take Drug Again, Overall Drug Liking) were assessed through eight hours postdose. Nasal irritation and safety were also assessed.

RESULTS

Relative to IN HM, the rate (Cmax) and extent (area under the curve [AUC0-last, AUC0-inf]) of exposure to hydromorphone following IN ASAL-HM were reduced by ≥50%. Consistent with these findings, scores on "at-the-moment" (i.e., Drug Liking Emax, High Emax) and retrospective (i.e., Take Drug Again, Overall Drug Liking) end points were statistically significantly lower for IN ASAL-HM, with mean/median differences ranging from 11.4 to 25.0 points. ASAL-HM produced greater nasal-related effects, such as nasal burning and facial pain, and a lower incidence of typical opioid-related adverse events such as euphoria, pruritus, and somnolence.

CONCLUSIONS

The novel hydromorphone prodrug ASAL-HM produced marked reductions in hydromorphone exposure and abuse-related effects following IN administration compared with HM. ASAL-HM has desirable molecular features for incorporation into putative abuse-deterrent immediate-release and extended-release hydromorphone products.

Pharmacokinetics and pharmacodynamics of hydromorphone after intravenous and intramuscular administration in horses

OBJECTIVE

To compare the pharmacokinetics and pharmacodynamics of hydromorphone in horses after intravenous (IV) and intramuscular (IM) administration.

STUDY DESIGN

Randomized, masked, crossover design.

ANIMALS

A total of six adult horses weighing [mean ± standard deviation (SD))] 447 ± 61 kg.

METHODS

Horses were administered three treatments with a 7 day washout. Treatments were hydromorphone 0.04 mg kg^⁻1 IV with saline administered IM (H-IV), hydromorphone 0.04 mg kg^⁻1 IM with saline IV (H-IM), or saline IV and IM (P). Blood was collected for hydromorphone plasma concentration at multiple time points for 24 hours after treatments. Pharmacodynamic data were collected for 24 hours after treatments. Variables included thermal nociceptive threshold, heart rate (HR), respiratory frequency (f_R), rectal temperature, and fecal weight. Data were analyzed using mixed-effects linear models. A p value of less than 0.05 was considered statistically significant.

RESULTS

The mean ± SD hydromorphone terminal half-life (t_1/2), clearance and volume of distribution of H-IV were 19 ± 8 minutes, 79 ± 12.9 mL minute^⁻1 kg^⁻1 and 1125 ± 309 mL kg^⁻1. The t_1/2 was 26.7 ± 9.25 minutes for H-IM. Area under the curve was 518 ± 87.5 and 1128 ± 810 minute ng mL^⁻1 for H-IV and H-IM, respectively. The IM bioavailability was 217%. The overall thermal thresholds for both H-IV and H-IM were significantly greater than P (p < 0.0001 for both) and baseline (p = 0.006). There was no difference in thermal threshold between H-IV and H-IM. No difference was found in physical examination variables among groups or in comparison to baseline. Fecal weight was significantly less than P for H-IV and H-IM (p = 0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

IM hydromorphone has high bioavailability and provides a similar degree of antinociception to IV administration. IM hydromorphone in horses provides a similar degree and duration of antinociception to IV administration.

Opioids in cancer-related pain: current situation and outlook

PURPOSE

Despite progress in treatments, cancer pain remains underestimated, poorly assessed and under-treated. Prescribing strong opioids, because of their specificities, requires precision in management considering their pharmacology but also a clear understanding of recommendations. Some clinicians highlight the risk of addiction, excessive sedation and respiratory depression and their need for information. Our objective in this review is to suggest some clinical guidance for the positioning and daily use of opioids within cancer pain management.

METHODS

Critical reflection based on literature analysis and clinical practice.

RESULTS

Strong opioids may be initiated as soon as pain diagnosis is defined. Factors to consider are pain aetiology, opioid pharmacokinetics and pharmacodynamics, genetic polymorphism, physiology (age, gender, weight and pregnancy), comorbidities (especially renal, hepatic, cardiovascular diseases), chronobiology, environmental factors, medication interference and treatment adherence. Achieving the best-balanced opioid treatment for background pain is complex, mainly due to the variable benefit/risk ratio between individuals and the experience of breakthrough cancer pain. Opioid initiation alongside a dynamic reassessment of pain should be fully integrated into the patient's management to optimise analgesia. The efficacy and safety of a strong opioid treatment need to be re-evaluated and adapted to individuals constantly as it varies over time.

CONCLUSIONS

Cancer pain is multimorphic and permanently changing due to disease evolution, curative treatments and disruptive events (concomitant treatments, pain from associated disease, comorbidities and complications, modifications of the environment). Well-managed opioids are the cornerstone of a complex environment requiring multidisciplinary dynamic assessments integrated into the patient's care pathway.

Continuing war on pain: a personalized approach to the therapy with nonsteroidal anti-inflammatory drugs and opioids

Successful pain management requires the delivery of analgesia with minimal risk of adverse drug reactions. Nonsteroidal anti-inflammatory drugs and opioids remain the mainstay of treatment for the majority of patients. Unfortunately, almost 50% of all patients experience inadequate pain relief and serious side effects. Allelic variants in genes coding for target proteins, transporters and enzymes, which govern analgesic drugs action and their fate in the organism, might explain inter-individual variability in pain severity and in drug-induced pain relief and toxicities. Additionally, it seems that epigenetic changes contribute to the highly variable response to pain treatment. Therefore, pharmacogenomic testing might be a valuable tool for personalization of pain treatment, with a multidisciplinary team approach involved.

The pharmacokinetics and pharmacodynamics of intravenous hydromorphone in horses

OBJECTIVE

Describe the pharmacokinetics and pharmacodynamics of intravenous hydromorphone in healthy horses.

STUDY DESIGN

Masked, randomized, cross-over, Latin square design.

ANIMALS

A group of eight healthy adult horses METHODS: Horses were administered each of four treatments with an 8 day washout. Treatments groups included intravenous hydromorphone 0.02 mg kg^-1 (LD), 0.04 mg kg^-1 (MD), 0.08 mg kg^-1 (HD) and saline (P). Blood samples for hydromorphone analysis were obtained for 24 hours after treatment. Plasma hydromorphone was quantified and pharmacokinetic parameters were determined using non-compartmental analysis. Pharmacodynamic data collected for 24 hours after treatment included thermal nociceptive threshold, heart rate (HR), respiratory rate (f_R) and rectal temperature, and analyzed using mixed-effects linear models.

RESULTS

Mean (± standard deviation) hydromorphone terminal half-life (t_1/2), systemic clearance and apparent volume of distribution at steady state (Vd_ss) were 18.1 ± 18.6, 34.0 ± 12.8, and 41.3 ± 32.5 minutes, 66.6 ± 5.3, 550.0 ± 76.4, and 92.7 ± 13.9 mL kg^-1 minute^-1, and 1118 ± 369, 1460 ± 325 and 2242 ± 950 mL kg^-1 for treatments LD, MD and HD, respectively. Thermal threshold increased significantly compared to baseline for all treatments for up to 12 hours. HR was elevated above baseline in treatments LD, MD and HD, extending to 30, 15 and 105 minutes after treatment, respectively. Respiratory rate was elevated above baseline in treatments MD and HD from 30 to 195 minutes and from 45 to 480 minutes after treatment, respectively. Temperature was elevated above baseline in treatment HD until 255 minutes after treatment.

CONCLUSIONS

Hydromorphone exhibited a short t_1/2, rapid clearance and large Vd_ss in horses. It also provided a dose-dependent increase in thermal threshold with associated increases in HR, f_R and rectal temperature.

CLINICAL RELEVANCE

Hydromorphone 0.04 mg kg^-1 provided clinically relevant thermal antinociception with minimal adverse effects.

Transition From Continuous Infusion Fentanyl to Hydromorphone in Critically Ill Patients

BACKGROUND

The 2013 Society of Critical Care Medicine guidelines for the management of pain, agitation, and delirium in adult intensive care unit (ICU) patients recommend intravenous opioids as first-line therapy to treat nonneuropathic pain. There is a paucity of literature describing possible benefits of utilizing specific opioids over others in ICU patients.

OBJECTIVE

The objective was to identify rationales for the transition from continuous infusion fentanyl to continuous infusion hydromorphone in critically ill patients.

METHODS

This was a single-center, prospective, observational analysis of adult ICU patients who were transitioned from fentanyl to hydromorphone. The major end point was to characterize the primary reason for transition. Minor end points included secondary reason(s) for transition, transition dosing, changes in continuous sedative requirements, and level of sedation.

RESULTS

Forty-six patients were included in the analysis. The primary rationale for transition was ventilator compliance (28.3%), followed by tachyphylaxis or better pain control (19.6%), and reduction in sedatives (13.0%). The most common secondary reason(s) for transition included reduction in sedatives (47.8%), opioid rotation (32.6%), and obesity (30.4). Median fentanyl rate of 100 µg/h was transitioned to 1 mg/h of hydromorphone. The percentage of patients requiring the use of continuous sedatives was decreased in the 24 hours following transition (P = .005); however, patients were more deeply sedated (P = .02).

CONCLUSION

Rationales for transition were to improve ventilator compliance, optimize patient-specific pharmacokinetics, and limit overall sedative exposure.

Characterizing the subjective, observer-rated, and physiological effects of hydromorphone relative to heroin in a human laboratory study

BACKGROUND

This study compared the effects of the several doses of the opioid agonists heroin and hydromorphone across two routes of administration in humans. The goal was to guide development of human laboratory studies of opioid effects and inform subsequent injection pharmacotherapy trials of hydromorphone-assisted treatment.

METHODS

A within-subject (N = 16), double-blind, double-dummy, placebo-controlled, evaluation of acute doses of heroin and hydromorphone was completed at four dose levels (placebo, low, medium, high) across two routes of administration (intravenous, subcutaneous) in non-physically dependent, opioid-experienced individuals. Subject and observer ratings, as well as physiological outcomes, were assessed.

RESULTS

Within each route of administration, heroin and hydromorphone produced effects that were qualitatively similar on most variables across the doses examined. All effects were dose-dependent. The drugs produced different effects on VAS ratings of "Feels Like Heroin," a Heroin Identification Test, observer agonist ratings, and oxygen saturation levels. Drug-dependent differences emerged at the highest doses in all cases. Few significant main effects of Route were identified and their pattern was not uniform. Relative potency calculations across all subject, observer, and physiological outcomes that met analysis criteria revealed similar profiles and resulted in mean heroin:hydromorphone potencies of 3.35:1 and 2.88:1 for the intravenous and subcutaneous routes, respectively, and intravenous:subcutaneous potencies of 0.47:1 and 0.49:1 for heroin and hydromorphone, respectively.

CONCLUSIONS

Hydromorphone produced similar subjective and physiological effects as heroin, but was more potent than heroin. The current findings support the use of hydromorphone as a model for heroin in human laboratory and clinical treatment studies, and help identify appropriate hydromorphone dose conversion ratios to produce effects qualitatively similar to heroin.

Opioid Conversions in Acute Care

Objective:

To discuss the historical basis and limitations of opioid conversion tables, review the relevant literature, and establish an evidence-based equianalgesic dose ratio (EDR) table for performing conversions in the acute care setting.

Data Sources:

Articles were identified through searches of MEDLINE (1966–January 2007) using the key words opioid, tolerance, conversion, dose, equianalgesic, equipotent, acute care, morphine, hydromorphone, fentanyl, methadone, and oxycodone. Additional references were located through a review of the bibliographies of articles cited and references cited in conversion tables.

Study Selection and Data Extraction:

All data sources identified were evaluated, and all information deemed relevant was included, with the exception of case series and case reports when higher level evidence was available.

Data Synthesis:

Opioid conversion tables are published in major textbooks, medical references, national guidelines, and review articles. Some conversion tables do not accurately reflect the dose ratios for which evidence is available. There is marginal evidence-based clinical data to support the dose ratios cited in these tables, particularly in the acute care setting where the clinical status of patients often changes rapidly. The barriers when performing route and opioid-to-opioid conversions in the acute care setting are formidable, but EDRs are provided, based on the best available evidence.

Conclusions:

In the acute care setting, calculation of dose ratios for opioids, based solely on opioid conversion tables, is an oversimplification of pain management, with a potential for adverse consequences. The calculation of EDRs is one step in an interdisciplinary process that must take into account patient- and institution-specific factors.

Two ortho-rhom-bic polymorphs of hydro-morphone

Conditions to obtain two polymorphic forms by crystallization from solution were determined for the analgesic drug hydro-morphone [C17H19NO3; systematic name: (4R,4aR,7aR,12bS)-9-hy-droxy-3-methyl-1,2,4,4a,5,6,7a,13-octa-hydro-4,12-methano-benzofuro[3,2-e]iso-quinolin-7-one]. These two crystalline forms, designated as I and II, belong to the P212121 ortho-rhom-bic space group. In both polymorphs, the hydro-morphone mol-ecules adopt very similar conformations with some small differences observed only in the N-methyl amine part of the mol-ecule. The crystal structures of both polymorphs feature chains of mol-ecules connected by hydrogen bonds; however, in form I this inter-action occurs between the hydroxyl group and the tertiary amine N atom whereas in form II the hydroxyl group acts as a donor of a hydrogen bond to the O atom from the cyclic ether part.

External Validation of a Recently Developed Population Pharmacokinetic Model for Hydromorphone During Postoperative Pain Therapy

BACKGROUND AND OBJECTIVE

We recently developed a new population pharmacokinetic model for hydromorphone in patients including age and bodyweight as covariates. The aim of the present study was to evaluate prospectively the predictive performance of this new model during postoperative pain therapy.

METHODS

This was a prospective, single-blinded, randomized, single-center study with two parallel arms. Fifty patients aged 40-85 years undergoing cardiac surgery involving thoracotomy were enrolled. Hydromorphone was administered postoperatively on the intensive care unit as target controlled infusion (TCI) for patient controlled analgesia (TCI-PCA) using the new pharmacokinetic model, or as conventional patient controlled analgesia (PCA). Arterial blood samples were taken for measurement of the hydromorphone plasma concentration. The predictive performance of the pharmacokinetic model was assessed by the median performance error (MDPE), the median absolute performance error (MDAPE), wobble and divergence. For comparison, the performance indices were also determined for three older models from the literature.

RESULTS

903 plasma concentrations of 41 patients were analyzed. The mean values (95 % CI) of MDPE, MDAPE, wobble and divergence for the new pharmacokinetic model were 11.2 % (3.9 to 18.7 %), 28.5 % (23.9 to 33.0 %), 21.4 % (18.0 to 24.9 %) and -1.6 %/h (-2.3 to -0.8 %/h). When compared with older models from the literature, performance was better with less overshoot after bolus doses.

CONCLUSION

The new pharmacokinetic model of hydromorphone showed a good precision and a better performance than older models. It is therefore suitable for TCI with hydromorphone during postoperative pain therapy.

TRIAL REGISTRATION

EudraCT 2013-002875-16, Clinical Trials NCT02035709.

Alternative routes to oral opioid administration in palliative care: a review and clinical summary

OBJECTIVE

A major goal of palliative care is to provide comfort, and pain is one of the most common causes of treatable suffering in patients with advanced disease. Opioids are indispensable for pain management in palliative care and can usually be provided by the oral route, which is safe, effective, and of lowest cost in most cases. As patients near the end of life, however, the need for alternate routes of medication increases with up to 70% of patients requiring a nonoral route for opioid administration. In order to optimize patient care, it is imperative that clinicians understand existing available options of opioid administration and their respective advantages and disadvantages.

METHODS

We performed a literature review to describe the most commonly used and available routes that can substitute for oral opioid therapy and to provide a summary of factors affecting choice of opioid for use in palliative care in terms of benefits, indications, cautions, and general considerations.

RESULTS

Clinical circumstances will largely dictate appropriateness of the route selected. When the oral route is unavailable, subcutaneous, intravenous, and enteral routes are preferred in the palliative care population. The evidence supporting sublingual, buccal, rectal, and transdermal gel routes is mixed.

CONCLUSIONS

This review is not designed to be a critical appraisal of the quality of current evidence; rather, it is a summation of that evidence and of current clinical practices regarding alternate routes of opioid administration. In doing so, the overarching goal of this review is to support more informed clinical decision making.

Pharmacogenetics of chronic pain management

OBJECTIVE

The experience of chronic pain is one of the commonest reasons individuals seek medical attention, making the management of chronic pain a major issue in clinical practice. Drug metabolism and responses are affected by many factors, with genetic variations offering only a partial explanation of an individual's response. There is a paucity of evidence for the benefits of pharmacogenetic testing in the context of pain management.

DESIGN AND METHODS

We reviewed the literature between 2000 and 2013, and references cited therein, using various keywords related to pain management, pharmacology and pharmacogenetics.

RESULTS

Opioids continue to be the mainstay of chronic pain management. Several non-opioid based therapies, such as treatment with cannabinoids, gene therapy and epigenetic-based approaches are now available for these patients. Adjuvant therapies with antidepressants, benzodiazepines or anticonvulsants can also be useful in managing pain. Currently, laboratory monitoring of pain management patients, if performed, is largely through urine drug measurements.

CONCLUSIONS

Drug half-life calculations can be used as functional markers of the cumulative effect of pharmacogenetics and drug-drug interactions. Assessment of half-life and therapeutic effects may be more useful than genetic testing in preventing adverse drug reactions to pain medications, while ensuring effective analgesia. Definitive, mass spectrometry-based methods, capable of measuring parent drug and metabolite levels, are the most useful assays for this purpose. Urine drug measurements do not necessarily correlate with serum drug concentrations or therapeutic effects. Therefore, they are limited in their use in monitoring efficacy and toxicity.

Population Pharmacokinetic Modeling of Hydromorphone in Cardiac Surgery Patients during Postoperative Pain Therapy

Background:

Hydromorphone is a µ-selective opioid agonist used in postoperative pain therapy. This study aimed to evaluate the pharmacokinetics of hydromorphone in cardiac surgery patients during postoperative analgesia with target-controlled infusion and patient-controlled analgesia.

Methods:

In this study, 50 adult patients were enrolled to receive intravenous hydromorphone during postoperative pain therapy. Arterial plasma samples were collected for measurements of drug concentration. Population pharmacokinetic parameters were estimated using nonlinear mixed-effects modeling. Results were validated and simulations were carried out to evaluate results.

Results:

Data from 49 patients (age range, 40–81 yr) were analyzed. The pharmacokinetics of hydromorphone were best described by a three-compartment model. Age was incorporated as a significant covariate for elimination clearance and central volume of distribution. Scaling all parameters with body weight improved the model significantly. The final estimates of the model parameters for the typical adult patient (67 yr old, weighing 70 kg) undergoing cardiac surgery were as follows: CL1 = 1.01 l/min, V1 = 3.35 l, CL2 = 1.47 l/min, V2 = 13.9 l, CL3 = 1.41 l/min, and V3 = 145 l. The elimination clearance decreased by 43% between the age of 40 and 80 yr, and simulations demonstrated that context-sensitive half-time increased from 26 to 84 min in 40- and 80-yr-old subjects, respectively.

Conclusions:

The final pharmacokinetic model gave a robust representation of hydromorphone pharmacokinetics. Inclusion of age and body weight to the model demonstrated a significant influence of these covariates on hydromorphone pharmacokinetics. The application of this patient-derived population model in individualized pain therapy should improve the dosing of hydromorphone in patients undergoing cardiac surgery.

Versatility of different pharmaceutical formulations of hydromorphone in the management of severe cancer pain and pain in palliative care

SUMMARY The management of severe pain situations requires therapeutic expertise in dealing with changes in pain intensity, analgesic limitations and individual patient needs. Opioids are the treatment of choice in severe pain. The availability of a broad range of opioids and formulations refined the options for improved pain treatment with a specific substance. These may include oral formulations, injectables and other applications suitable for different patient needs. Moreover, variable drug concentrations are most useful in clinical practice. This article briefly reviews the versatility of different hydromorphone formulations in the management of severe pain in palliative care and cancer. Limiting strong opioid treatment with one opioid substance in different formulations (adjuvants if necessary), according to varying requirements of patients, would be eligible for achieving a well-tolerated and effective pain therapy. Its versatility renders hydromorphone suitable for consistent opioid administration with predictable substance release, and may thus contribute to reducing the need for opioid change.

Intranasal drug delivery: an efficient and non-invasive route for systemic administration: focus on opioids

Intranasal administration is a non-invasive route for drug delivery, which is widely used for the local treatment of rhinitis or nasal polyposis. Since drugs can be absorbed into the systemic circulation through the nasal mucosa, this route may also be used in a range of acute or chronic conditions requiring considerable systemic exposure. Indeed, it offers advantages such as ease of administration, rapid onset of action, and avoidance of first-pass metabolism, which consequently offers for example an interesting alternative to intravenous, subcutaneous, oral transmucosal, oral or rectal administration in the management of pain with opioids. Given these indisputable interests, fentanyl-containing formulations have been recently approved and marketed for the treatment of breakthrough cancer pain. This review will outline the relevant aspects of the therapeutic interest and limits of intranasal delivery of drugs, with a special focus on opioids, together with an in-depth discussion of the physiological characteristics of the nasal cavity as well as physicochemical properties (lipophilicity, molecular weight, ionisation) and pharmaceutical factors (absorption enhancers, devices for application) that should be considered for the development of nasal drugs.

Comparative clinical effects of hydromorphone and morphine: a meta-analysis

We have conducted a meta-analysis of the clinical effects of morphine and hydromorphone to compare their benefit in analgesia. Embase and Medline were searched with an end-date of June 2009 for randomized, controlled trials or observational studies that addressed comparative analgesic and side-effects or particular side-effects. Two researchers independently identified included studies and extracted the data. Estimates of opioid effects were combined by using a random-effects model. Meta-analysis of eight studies suggested that hydromorphone (494 patients) provides slightly better (P=0.012) clinical analgesia than morphine (510 patients). The effect-size was small (Cohen's d=0.266) and disappeared when one study was removed, although the advantage of hydromorphone was more evident in studies of better quality (Jadad's rating). Side-effects were similar, for example, nausea (P=0.383, nine studies, 456 patients receiving hydromorphone and 460 morphine); vomiting (P=0.306, six studies, 246 patients receiving hydromorphone and 239 morphine); or itching (P=0.249, eight studies, 405 patients receiving hydromorphone, 410 morphine). This suggests some advantage of hydromorphone over morphine for analgesia. Additional potential clinical pharmacological advantages with regard to side-effects, such as safety in renal failure or during acute analgesia titration, are based on limited evidence and require substantiation by further studies.

[Intranasal delivery of systemic drugs: a new route for opioid drugs]

The intranasal delivery of drugs is widely used for the local treatment of rhinitis or nasal polyposis. This route of delivery could represent an interesting alternative for systemic drugs with low digestive absorption. The nasal mucosa acts as an anatomical obstacle hard to get over, except for compounds with low molecular weight or highly lipophilic. Among morphinic drugs, fentanyl, very lipophilic, is rapidly absorbed via intranasal administration with a bioavailability close to 90%. This route of delivery for fentanyl is a new alternative for the treatment of breakthrough pain and gives the opportunity to discuss on the interest and the limits of nasal route administration of drugs, particularly of opioids.

Recent advances in the use of opioids for cancer pain

Opioids are the mainstay of treatment for moderate to severe cancer pain. In recent years there have been many advances in the use of opioids for cancer pain. Availability and consumption of opioids have increased and opioids other than morphine (including methadone, fentanyl, oxycodone) have become more widely used. Inter-individual variation in response to opioids has been identified as a significant challenge in the management of cancer pain. Many studies have been published demonstrating the benefits of opioid switching as a clinical maneuver to improve tolerability. Constipation has been recognized as a significant burden in cancer patients on opioids. Peripherally restricted opioid antagonists have been developed for the prevention and management of opioid induced constipation. The phenomenon of breakthrough pain has been characterized and novel modes of opioid administration (transmucosal, intranasal, sublingual) have been explored to facilitate improved management of breakthrough cancer pain. Advances have also been made in the realm of molecular biology. Pharmacogenetic studies have explored associations between clinical response to opioids and genetic variation at a DNA level. To date these studies have been small but future research may facilitate prospective prediction of response to individual drugs.

Patient-controlled analgesia in the management of postoperative pain

Patient-controlled analgesia (PCA) is a delivery system with which patients self-administer predetermined doses of analgesic medication to relieve their pain. Since its introduction in the early 1980s, the daily management of postoperative pain has been extensively optimised. The use of PCA in hospitals has been increasing because of its proven advantages over conventional intramuscular injections. These include improved pain relief, greater patient satisfaction, less sedation and fewer postoperative complications. All PCA modes contain the following variables: initial loading dose, demand dose, lockout interval, background infusion rate and 1-hour or 4-hour limits. Morphine is the most studied and most commonly used intravenous drug for PCA. In spite of the fact that it is the 'first choice' for PCA, other opioids have been successfully used for this option. The most observed adverse effects of opioid-based PCA are nausea and vomiting, pruritus, respiratory depression, sedation, confusion and urinary retention. Although intravenous PCA is the most studied route of PCA, alternative routes have extensively been described in the literature. PCA by means of peridural catheters and peripheral nerve catheters are the most studied. Recently, transdermal PCA has been described. The use of peripheral or neuraxial nerve blocks is recommended to avoid the so called opioid tolerance observed with the intravenous administration of opioids. Numerous studies have shown the superiority of epidural PCA to intravenous PCA. The beneficial postoperative effects of epidural analgesia are more apparent for high-risk patients or those undergoing higher risk procedures. PCA with peripheral nerve catheters results in increased postoperative analgesia and satisfaction for surgery on upper and lower extremities. Serious complications occur rarely with these catheters. With the introduction of an Acute Pain Service, management of postoperative pain can be improved. This will also help to minimise adverse effects related to PCA and to avoid lethal mishaps.

Pharmacokinetic investigation of dose proportionality with a 24-hour controlled-release formulation of hydromorphone

Background

The purpose of this study was investigate the dose proportionality of a novel, once-daily, controlled-release formulation of hydromorphone that utilizes the OROS^® Push-Pull™ osmotic pump technology.

Methods

In an open-label, four-way, crossover study, 32 healthy volunteers were randomized to receive a single dose of OROS^® hydromorphone 8, 16, 32, and 64 mg, with a 7-day washout period between treatments. Opioid antagonism was provided by three or four doses of naltrexone 50 mg, given at 12-hour intervals pre- and post-OROS^® hydromorphone dosing. Plasma samples for pharmacokinetic analysis were collected pre-dose and at regular intervals up to 48 hours post-dose (72 hours for the 64-mg dose), and were assayed for hydromorphone concentration to determine peak plasma concentration (C_max), time at which peak plasma concentration was observed (T_max), terminal half-life (t_1/2), and area under the concentration-time curve for zero to time t (AUC_0-t) and zero to infinity (AUC_0–∞). An analysis of variance (ANOVA) model on untransformed and dose-normalized data for AUC_0-t, AUC_0–∞, and C_max was used to establish dose linearity and proportionality.

Results

The study was completed by 31 of 32 subjects. Median T_max (12.0–16.0 hours) and mean t_1/2 (10.6–11.0 hours) were found to be independent of dose. Regression analyses of C_max, AUC_0–48, and AUC_0–∞ by dose indicated that the relationship was linear (slope, P ≤ 0.05) and that the intercept did not differ significantly from zero (P > 0.05). Similar analyses with dose-normalized parameters also indicated that the slope did not differ significantly from zero (P > 0.05).

Conclusion

The pharmacokinetics of OROS^® hydromorphone are linear and dose proportional for the 8, 16, 32, and 64 mg doses.

Trial Registration

Clinical Trials.gov NCT00398957

Managing Cancer Pain and Symptoms of Outpatients by Rotation to Sustained-release Hydromorphone

PURPOSE

In this prospective clinical trial we examined the technique of opioid rotation to oral sustained-release hydromorphone for controlling pain and symptoms in outpatients with cancer pain.

METHODS

Before and after rotation, 50 patients were assessed by Numerical Analog Scales [Numerical Rating Scales (NRS)], or as categorical parameters, and analyzed by descriptive and confirmatory statistics (ANOVA, Wilcoxon, chi).

RESULTS

Rotation was successful in 64% of patients experiencing pain (60%), and gastrointestinal (32%) and central (26%) symptoms under oral morphine (38%), transdermal fentanyl (22%), tramadol (20%), oxycodone (12%), or sublingual buprenorphine (8%). NRS of pain (4.1 to 3.2; P=0.015), gastrointestinal symptoms, especially defecation rates (P=0.04), and incidence of insomnia improved after an increase in morphine-equivalent doses from 108.9 to 137.6 mg/d without modifying concomitant analgesics or coanalgesics.

CONCLUSIONS

Switching the opioid to oral hydromorphone may be a helpful technique to alleviate pain and several symptoms, but it is still not clear to what extent the underlying mechanisms, such as the technique of rotation itself, better dose adjustment, or using a different opioid have an impact.

Capillary electrophoresis contributions to the hydromorphone metabolism in man

CE-ESI multistage IT-MS (CE-MS(n), n < or = 4) and computer simulation of fragmentation are demonstrated to be effective tools to detect and identify phase I and phase II metabolites of hydromorphone (HMOR) in human urine. Using the same CE conditions as previously developed for the analysis of urinary oxycodone and its metabolites, HMOR and its phase I metabolites produced by N-demethylation, 6-keto-reduction and N-oxidation and phase II conjugates of HMOR and its metabolites formed with glucuronic acid, glucose, and sulfuric acid could be detected in urine samples of a patient that were collected during a pharmacotherapy episode with daily ingestion of 48 mg of HMOR chloride. The CE-MS(n) data obtained with the HMOR standard, synthesized hydromorphol and hydromorphone-N-oxide, and CYP3A4 in vitro produced norhydromorphone were employed to identify the metabolites. This approach led to the identification of previously unknown HMOR metabolites, including HMOR-3O-glucide and various N-oxides, structures for which no standard compounds or mass spectra library data were available. Furthermore, the separation of alpha- and beta-hydromorphol, the stereoisomers of 6-keto-reduced HMOR, was achieved by CE in the presence of the single isomer heptakis(2,3-diacetyl-6-sulfato)-beta-CD. The obtained data indicate that the urinary excretion of alpha-hydromorphol is larger than that of beta-hydromorphol.

Pain management

This article provides information regarding treatments for the management of moderate to severe pain in patients who are at the end of life. Discussion focuses on the use of strong opioids and adjuvant analgesics. Special attention also is given to the most frequently used forms of interventional pain management. Although pain in terminally ill patients is not always related to cancer, many of the studies cited in this article were performed in cancer patients, a model that informs much of what is presented.

Patient-controlled analgesia

One of the most common methods for providing postoperative analgesia is via patient-controlled analgesia (PCA). Although the typical approach is to administer opioids via a programmable infusion pump, other drugs and other modes of administration are available. This article reviews the history and practice of many aspects of PCA and provides extensive guidelines for the practice of PCA-administered opioids. In addition, potential adverse effects and recommendations for their monitoring and treatment are reviewed.

Comparative efficacy of oral extended-release hydromorphone and immediate-release hydromorphone in patients with persistent moderate to severe pain: two randomized controlled trials

Two multicenter, randomized, double-blind, crossover studies with identical designs evaluated the efficacy of oral extended-release hydromorphone (HHER) administered q24h compared with immediate-release hydromorphone (HHIR) dosed four times daily in patients with persistent moderate to severe pain. Patients titrated to a stable HHER dose were randomized to individualized doses of HHER or HHIR for 3 to 7 days before crossover to the second treatment. Primary efficacy end point was the mean of average pain intensity (API) scores, rated on a 0- to 10-point numeric scale, over the last 2 days before the pharmacokinetics/pharmacodynamics day of each double-blind period. Difference between treatments (HHER - HHIR) in study 1 was 0.17 with a 90% confidence interval (CI) (-0.01, 0.34); in study 2, difference was 0.07 with a 90% CI (-0.12, 0.26). There were no significant differences between treatments in API scores or amount of rescue medication used at any time interval within the 24-hour dosing period. No reduction in pain control occurred in patients administered HHER at the end of the 24-hour dosing period. Most treatment-emergent adverse events were opioid-related. In these studies, HHER administered q24h and HHIR dosed four times daily provided comparable analgesia at an equivalent total daily dose.

A Multiple-Dose Phase I Study of Intranasal Hydromorphone Hydrochloride in Healthy Volunteers

We evaluated the pharmacokinetics, tolerability, and safety of 1 and 2 mg of intranasal hydromorphone hydrochloride in an open-label, single- and multiple-dose study. This Phase I study was conducted in 24 healthy volunteers (13 men and 11 women). Intranasal doses were delivered as 0.1-mL metered-dose sprays into one or both nostrils for 1- and 2-mg doses, respectively. Venous blood samples were taken serially from 0 to 12 h after the first single dose and the last (seventh) multiple dose. Plasma hydromorphone concentrations were determined by liquid chromatography/mass spectrometry/mass spectrometry. Noncompartmental analysis was used to estimate pharmacokinetic variables. After 7 intranasal doses of 1 and 2 mg (once every 6 h), mean +/- sd peak plasma concentrations of 2.8 +/- 0.7 ng/mL and 5.3 +/- 2.3 ng/mL, respectively, were observed. The median time to peak concentration was 20 min for both single and multiple doses. Dose proportionality was observed for the 1- and 2-mg doses. Adverse events included somnolence, dizziness, and bad taste after dose administration. Intranasal hydromorphone hydrochloride was well tolerated and demonstrated rapid nasal drug absorption and predictable accumulation. These results support clinical investigation of hydromorphone hydrochloride nasal spray for use as an alternative to oral and IM administration.

Pharmacokinetic and pharmacodynamic evaluation of intravenous hydromorphone in cats1

This study describes the pharmacokinetics of intravenous hydromorphone in cats and the simultaneous measurement of antinociceptive pharmacodynamic effects using a thermal threshold testing system. Following establishment of a baseline thermal threshold, six adult cats were administered 0.1 mg/kg of hydromorphone intravenously. Thermal threshold testing and blood collection were conducted simultaneously at predetermined time points. Plasma hydromorphone concentrations were determined by a liquid chromatographic-mass spectral method and pharmacokinetic analysis was performed by nonlinear least squares regression analysis. Plasma hydromorphone concentrations declined rapidly over time, and were below the limit of quantification of the assay (LOQ = 1.0 ng/mL) by 360 min. In contrast, thermal thresholds rose from a pretreatment value of 40.9 +/- 0.65 degrees C (mean +/- SEM) to instrument cut-out (55 degrees C) within 15 min and remained significantly elevated from 15-450 min after treatment. Inspection of the data revealed no direct correlation between plasma hydromorphone concentrations and the antinociceptive effect of this drug in cats. These findings support the importance of conducting pharmacokinetic studies in parallel with objective measurements of drug effect.

Effect of fluticasone propionate nasal spray on bioavailability of intranasal hydromorphone hydrochloride in patients with allergic rhinitis

STUDY OBJECTIVE

To investigate the effect of the nasal corticosteroid fluticasone propionate on the bioavailability and pharmacokinetics of single-dose intranasal hydromorphone hydrochloride in patients with allergic rhinitis.

DESIGN

Randomized, three-way, crossover pharmacokinetic study.

SETTING

University clinical research unit.

PATIENTS

Twelve patients with allergic rhinitis.

INTERVENTION

Hydromorphone hydrochloride 2.0 mg was administered by intravenous infusion (treatment A), intranasal spray without allergic rhinitis treatment (treatment B), and intranasal spray after 6 days of fluticasone propionate (treatment C). Blood samples were collected serially from 0-16 hours.

MEASUREMENTS AND MAIN RESULTS

Pharmacokinetic parameters were determined by noncompartmental methods. An analysis of variance (ANOVA) model was used for statistical analysis. Mean (% coefficient of variation) absolute bioavailability of intranasal hydromorphone was 51.9% (28.2) and 46.9% (30.3) in patients with allergic rhinitis with and without treatment with fluticasone propionate, respectively. Mean maximum concentration (Cmax) values were 3.02 and 3.56 ng/ml, respectively. No statistical differences in Cmax and area under the concentration versus time curve were detected between intranasal treatments. Bioavailability values for both intranasal treatments were lower than those in healthy volunteers (57%). Median time to Cmax (Tmax) values were significantly different (p=0.02) for treatments B and C (15 and 30 min, respectively) using rank-transformed Tmax for ANOVA. Adverse effects were consistent with known effects of hydromorphone administered by other routes, with the exception of bad taste after intranasal administration.

CONCLUSION

Hydromorphone was rapidly absorbed after nasal administration, with maximum concentrations occurring for most subjects within 30 minutes. Allergic rhinitis may affect pain management strategies for intranasal hydromorphone, with a delay in onset of action for patients treated with fluticasone propionate.

Bioavailability and Pharmacokinetics of Intranasal Hydromorphone in???Patients Experiencing Vasomotor Rhinitis

BACKGROUND AND OBJECTIVE

Narcotic analgesics such as hydromorphone undergo an extensive first-pass effect resulting in a low systemic bioavailability following oral administration. Alternative dosing routes, such as rectal and intranasal (IN) routes, have been suggested as options for oral or intravenous administration. Rhinitis and pharmacological agents used for treatment are considered factors that could alter the rate and extent of absorption of drugs administered by the nasal route. The purpose of this study was to evaluate the pharmacokinetics of intranasal hydromorphone hydrochloride (HCl) in patients with vasomotor rhinitis.

METHODS

Ten patients completed the randomised, three-way crossover study. During the three treatment periods, a single dose of hydromorphone HCl 2.0mg was administered via intravenous infusion (treatment A) and the intranasal route without (treatment B) or with (treatment C) vasoconstrictor pretreatment for rhinitis. Blood samples were collected serially from 0 to 16 hours. Noncompartmental methods were used to determine pharmacokinetic parameters.

RESULTS

Maximum plasma concentrations were 3.69 and 3.38 mug/L for treatments B and C, respectively. Mean (% coefficient of variation) bioavailability of intranasal hydromorphone was 54.4% (34.8) and 59.8% (22.1) with and without pretreatment, respectively. Pretreatment of rhinitis did not significantly affect the rate or extent of absorption of hydromorphone in this study. There was not a significant difference in bioavailability between treated and untreated rhinitis.

CONCLUSIONS

This study found intranasal administration of hydromorphone in patients experiencing vasomotor rhinitis had acceptable bioavailability and a pharmacokinetic profile comparable to previous studies. These data support further investigation of this single-dose delivery system for clinical use.

Extemporaneous compounding of pain and symptom control medications

This paper introduces a new series in the Journal on extemporaneously compounded dosage forms for symptom control. Some advantages and limitations of compounded medications are described and issues that clinicians should consider are mentioned. Topics that will be discussed in future papers in this series are described. Changes of compounding-related chapters of the United States Pharmacopeia from advisory statements to enforceable standards are discussed. As an example of important formulation considerations, some physical-chemical characteristics and route of administration characteristics of opioid analgesics are discussed.

Pharmacokinetics and bioavailability of single-dose intranasal hydromorphone hydrochloride in healthy volunteers

We evaluated pharmacokinetics and absolute bioavailability of single doses of hydromorphone hydrochloride after administration of 1.0 and 2.0 mg of intranasal (IN) and 2.0 mg of IV hydromorphone hydrochloride. An open-label, randomized, three-way crossover study was conducted in 24 healthy volunteers (13 men and 11 women). IN doses were delivered as 0.1-mL metered-dose sprays into one or both nostrils for 1.0- and 2.0-mg doses, respectively. Blood samples were taken serially from 0 to 16 h after each dose. Plasma hydromorphone concentrations were determined by liquid chromatography-mass spectrometry-mass spectrometry. Noncompartmental analysis was used to estimate pharmacokinetic variables. Mean hydromorphone bioavailabilities and percent coefficient of variation of 52.4% (22.7) and 57.5% (18.6) were seen after the 1.0- and 2.0-mg IN doses, respectively. Median times to maximum concentration were 20 and 25 min for IN doses. Adverse events included somnolence and dizziness with all routes of administration and a bad taste after IN doses. Dose proportionality for the 1.0- and 2.0-mg IN doses was observed. IN hydromorphone hydrochloride met the minimum requirements for safety and demonstrated rapid nasal drug absorption and clinically relevant bioavailability. Results support further development of this novel hydromorphone hydrochloride nasal spray.

IMPLICATIONS

Pharmacokinetics and bioavailability were determined for two doses of intranasal hydromorphone in healthy volunteers. Rapid, reliable absorption, and predictable pharmacokinetics support the investigation of hydromorphone hydrochloride nasal spray as a therapeutic alternative to oral and IM administration.

Demographics, assessment and management of pain in the elderly

The prevalence of pain increases with each decade of life. Pain in the elderly is distinctly different from pain experienced by younger individuals. Cancer is a leading cause of pain; however, other conditions that cause pain such as facet joint arthritis (causing low back pain), polymyalgia rheumatica, Paget's disease, neuropathies, peripheral vascular disease and coronary disease most commonly occur in patients over the age of 50 years. Poorly controlled pain in the elderly leads to cognitive failure, depression and mood disturbance and reduces activities of daily living. Barriers to pain management include a sense of fatalism, denial, the desire to be 'the good patient', geographical barriers and financial limitations. Aging causes physiological changes that alter the pharmacokinetics and pharmacodynamics of analgesics, narrowing their therapeutic index and increasing the risk of toxicity and drug-drug interactions. CNS changes lead to an increased risk of delirium. Assessment among the verbal but cognitively impaired elderly is satisfactorily accomplished with the help of unidimensional and multidimensional pain scales. A comprehensive physical examination and pain history is essential, as well as a review of cognitive function and activities of daily living. The goal of pain management among the elderly is improvement in pain and optimisation of activities of daily living, not complete eradication of pain nor the lowest possible drug dosages. Most successful management strategies combine pharmacological and nonpharmacological (home remedies, massage, topical agents, heat and cold packs and informal cognitive strategies) therapies. A basic principle of the pharmacological approach in the elderly is to start analgesics at low dosages and titrate slowly. The WHO's three-step guideline to pain management should guide prescribing. Opioid choices necessitate an understanding of pharmacology to ensure safe administration in end-organ failure and avoidance of drug interactions. Adjuvant analgesics are used to reduce opioid adverse effects or improve poorly controlled pain. Adjuvant analgesics (NSAIDs, tricyclic antidepressants and antiepileptic drugs) are initiated prior to opioids for nociceptive and neuropathic pain. Preferred adjuvants for nociceptive pain are short-acting paracetamol (acetaminophen), NSAIDs, cyclo-oxygenase-2 inhibitors and corticosteroids (short-term). Preferred drugs for neuropathic pain include desipramine, nortriptyline, gabapentin and valproic acid. Drugs to avoid are pentazocine, pethidine (meperidine), dextropropoxyphene and opioids that are both an agonist and antagonist, ketorolac, indomethacin, piroxicam, mefenamic acid, amitriptyline and doxepin. The type of pain, and renal and hepatic function, alter the preferred adjuvant and opioid choices. Selection of the appropriate analgesics is also influenced by versatility, polypharmacy, severity and type of pain, drug availability, associated symptoms and cost.

Postoperative hypoxemia and hypercarbia in healthy dogs undergoing routine ovariohysterectomy or castration and receiving butorphanol or hydromorphone for analgesia

OBJECTIVE

To determine frequency and severity of postanesthetic hypoxemia and hypercarbia in healthy dogs undergoing elective ovariohysterectomy or castration and given butorphanol or hydromorphone for analgesia.

DESIGN

Prospective trial.

ANIMALS

0 healthy dogs weighing > 10 kg (22 lb).

PROCEDURE

Dogs were anesthestized with acepromazine, glycopyrrolate, thiopental, and isoflurane, and butorphanol (n = 10) or hydromorphone (10) was used for perioperative analgesia. Arterial blood gas analyses were performed 10 and 30 minutes and 1, 2, 3, and 4 hours after extubation.

RESULTS

In dogs that received hydromorphone, mean PaCO2 was significantly higher, compared with the preoperative value, 10 and 30 minutes and 1, 2, and 3 hours after extubation. Mean PaCO2 was significantly higher in dogs given hydromorphone rather than butorphanol 10 and 30 minutes and 1 and 2 hours after extubation. Mean PaO2 was significantly lower, compared with preoperative values, 30 minutes and 1 and 2 hours after extubation in dogs given hydromorphone and 30 minutes after extubation in dogs given butorphanol. Mean PaO2 was significantly lower in dogs given hydromorphone rather than butorphanol 1 hour after extubation. Four dogs had PaO2 < 80 mm Hg 1 or more times after extubation.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that administration of hydromorphone to healthy dogs undergoing elective ovariohysterectomy or castration may result in transient increases in PaCO2 postoperatively and that administration of hydromorphone or butorphanol may result in transient decreases in PaO2. However, increases in PaCO2 and decreases in PaO2 were mild, and mean PaCO2 and PaO2 remained within reference limits.

Hydromorphone transfer into breast milk after intranasal administration

STUDY OBJECTIVES

To determine the distribution of hydromorphone into breast milk and the potential exposure of the suckling infant, and whether the distribution of hydromorphone into milk can be predicted accurately by a passive diffusion model.

DESIGN

Single-dose, pharmacokinetic study.

SETTING

University clinical research unit.

PATIENTS

Eight lactating, nonsmoking, healthy women aged 24-32 years.

INTERVENTION

Hydromorphone HCl 2 mg was given intranasally to the women to characterize its pharmacokinetics and extent of its transfer into breast milk.

MEASUREMENTS AND MAIN RESULTS

Plasma and milk samples were analyzed using liquid chromatography with tandem mass spectrometry detection. The milk:plasma ratio (M:P) was calculated as the total area under the concentration-time curve (AUC) of the milk divided by the total AUC of the plasma. Predicted in vitro M:P ratios were calculated using a diffusion model. Protein binding in milk and plasma, partitioning into milk fat (whole milk:skim milk ratios), as well as pH partitioning between plasma and milk were incorporated in the model. Protein binding was determined by equilibrium dialysis. Protein binding was minimal in both milk and plasma, with unbound fractions of 1 and 0.84, respectively There was little partitioning into milk fat, as demonstrated by the whole milk:skim milk ratio of 0.98. The observed and predicted M:P ratios +/- SD for hydromorphone were 2.57 +/- 0.47 and 1.11 +/- 0.28, respectively. The 95% confidence interval for the observed M:P ratio overlapped the confidence interval of the predicted M:P ratio, a finding that supports a role for both passive diffusion and active transport as mechanisms of hydromorphone transfer into milk.

CONCLUSION

Hydromorphone distributes rapidly from plasma into breast milk; however, the drug does not partition into fat. The suckling infant would receive approximately 0.67% of the maternal dose of hydromorphone (adjusted for body weight). As this is a limited exposure, further studies are needed to determine any potential impact to an infant who is fed breast milk from a mother treated with hydromorphone.

Hydromorphone metabolites: isolation and identification from pooled urine samples of a cancer patient

1. Hydromorphone-3-glucuronide, dihydromorphine, dihydroisomorphine, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide were isolated from a cancer patient's urine and identified as metabolites of hydromorphone by comparison with synthetic standards using LC/MS/MS with gradient elution. 2. The relative urinary recovery of dihydroisomorphine-3-glucuronide was estimated to be 17-fold higher than previously reported. 3. Three new metabolites, including hydromorphone-3-sulphate, norhydromorphone and nordihydroisomorphine, were tentatively identified.

LC-MS-MS analysis of hydromorphone and hydromorphone metabolites with application to a pharmacokinetic study in the male Sprague-Dawley rat

1. A high performance liquid chromatography-mass spectrometry-mass spectrometry (LC-MS-MS) assay was developed for the analysis of hydromorphone and its metabolites, namely dihydromorphine, dihydroisomorphine, hydromorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide, in rat plasma samples. 2. Analytes were extracted by solid-phase extraction using C2 cartridges. The extraction recoveries were > 76% for all analytes. Both intra- and interassay variabilities were < or = 12%. Using a plasma sample size of 100 microl, the limits of detection were 7.0 nmol(-1) (2.0 ng ml(-1)) for hydromorphone, dihydromorphine and dihydroisomorphine and 11 nmol l(-1) (5.0 ng ml l(-1)) for hydrormorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorhine-3-glucuronide at a signal-to-noise ratio = 3. 3. The present assay was applied to a pharmacokinetic study in rat after intraperitoneal administration of hydromorphone.

Development and validation of a sensitive method for hydromorphone in human plasma by normal phase liquid chromatography-tandem mass spectrometry

Liquid chromatography coupled with tandem mass spectrometry (LC-MS-MS) was developed for the quantitation of hydromorphone (HYD), an opiate analgesic, in human plasma. A simple liquid-liquid extraction was used to extract the analyte and its deuterated internal standard (d3-HYD). Chromatographic separation of hydromorphone from its metabolite hydromorphone-3-glucuronide (H3G) was necessary because of the significant H3G fragmentation to HYD before Ql of the mass spectrometer, which could result in false detection as HYD in the multiple reaction mode (MRM). This separation was achieved using a 50 x 2 mm, I.D. silica column (5 microm) and a mobile phase of acetonitrile-water formic acid (80:20:1, v/v/v). The method was validated in the concentration range 0.05-10 ng ml(-1) in plasma and met the acceptance criteria of industry guidelines for accuracy, precision, and stability.

In vitro and in vivo studies of subcutaneous hydromorphone implants designed for the treatment of cancer pain

Unrelieved cancer pain remains a significant problem worldwide. Patients receive inadequate analgesia for a variety of complex and multifactorial reasons. Limited availability of opioids secondary to concerns about potential diversion of these medications for illicit use and poor compliance with oral regimens are significant factors in many countries. This study was designed to develop and test an implantable opioid delivery device capable of releasing a potent opioid subcutaneously at a continuous rate for 4 weeks. A low temperature solvent casting technique was used to formulate ethylene vinyl acetate (EVA) copolymer disks containing 50% hydromorphone by weight. The release characteristics of disks of different height and diameter, coated and uncoated, and with and without a central uncoated channel were studied. The effect of temperature and pH were also evaluated. In vitro assessments were conducted in phosphate buffer using UV spectrophotometry. In vivo studies employed New Zealand White Rabbits and a radioimmunoassay. Plasma levels following hydromorphone delivery by polymer, osmotic pump, and intravenous administration were compared. In vitro, uncoated EVA polymer disks measuring 1.05 cm in diameter and 0.27 cm in height released an initial large burst of hydromorphone. Coating the disks with 100-200 microM of poly(methyl-methacrylate) prevented drug egress from the polymer. A central uncoated channel measuring 1.25 mm in diameter in an otherwise coated polymer virtually eliminated the initial burst of drug release and provided near zero-order hydromorphone release at an average rate of 164 micrograms per hour for 4 weeks. Doubling the height of the polymer approximately doubled the release rate while doubling the diameter of the polymer extended the duration of drug release to over 8 weeks. In rabbits, stable plasma hydromorphone concentrations (23-37 ng/ml) were sustained for 4 weeks following implantation of 2 polymers with an uncoated central channel. No initial burst of hydromorphone release was noted. Increasing the number of polymers produced sustained and predictable increases in plasma hydromorphone concentrations. Plasma levels were similar with subcutaneous hydromorphone delivered by polymer and osmotic pump and much less variable than with intravenous bolus hydromorphone. A uniquely configured implantable drug delivery device has been developed using materials which are approved for human use. It safely and reproducibly releases hydromorphone for weeks in vitro and in vivo without an initial burst of drug release. Varying the thickness, diameter, and number of implants provides flexibility in the release rate and duration of release. This implantable opioid delivery device could provide a sustained subcutaneous infusion of hydromorphone to patient with cancer pain in developed and developing nations without pumps, catheters, or extensive outpatient support services. In addition, it should improve compliance and reduce concern regarding illicit diversion of opioids.

Steady-state pharmacokinetics of hydromorphone and hydromorphone-3-glucuronide in cancer patients after immediate and controlled-release hydromorphone

Although the pharmacokinetics of oral hydromorphone has been evaluated in healthy volunteers after small single oral doses, data are not available regarding the disposition of hydromorphone and its principal metabolite, hydromorphone-3-glucuronide (H3G), at steady-state and after large oral doses. The authors studied the pharmacokinetics of hydromorphone and H3G after oral administration of an immediate-release (IR) and controlled-release (CR) formulation of hydromorphone at a daily dose of 48 +/- 11 mg (range 6-216 mg) in a randomized, double-blind, steady-state, two-way crossover evaluation in 18 patients with chronic cancer pain. Controlled-release hydromorphone demonstrated equivalent bioavailability and acceptable CR characteristics, when compared with IR hydromorphone (CR vs. IR: AUC0-12 123.10 +/- 20.38 vs. 118.98 +/- 20.92 ng.hr.mL-1, P = NS, Cmax 17.76 +/- 3.07 vs. 19.70 +/- 4.04 ng.mL-1, P = NS, Cmin 6.04 +/- 1.01 vs. 5.28 +/- 1.000 ng.mL-1, P = NS, and Tmax 4.78 +/- 0.78 vs. 1.47 +/- 0.22 hr, P = 0.0008). A significant linear relationship existed between hydromorphone dose and hydromorphone AUC (r = 0.8315, P = 0.0001) and between hydromorphone AUC and H3G AUC (r = 0.8048, P = 0.0001) over a wide dose range. The steady-state molar ratio of H3G to hydromorphone was 27:1. The authors conclude that CR hydromorphone provides a pharmacokinetic profile consistent with 12 hourly dosing and that at steady state, oral hydromorphone is extensively metabolized to H3G, although the pharmacologic activity of this metabolite remains unknown.

Comparative clinical efficacy and safety of immediate release and controlled release hydromorphone for chronic severe cancer pain

BACKGROUND

The short elimination half-life of hydromorphone necessitates 4-hourly dosing to maintain optimal levels of analgesia in patients with chronic cancer pain. The purpose of this study was to compare the clinical efficacy and safety of controlled release hydromorphone administered every 12 hours and immediate release hydromorphone administered every 4 hours in patients with chronic severe cancer pain.

METHODS

Forty-eight patients with stable chronic severe cancer pain were randomized, in a double-masked crossover study, to controlled release hydromorphone every 12 hours or immediate release hydromorphone every 4 hours for 7 days each. Pain intensity was assessed using a visual analog scale (VAS) and the Present Pain Intensity Index of the McGill Pain Questionnaire. Nausea and sedation were also assessed using a VAS. Assessments were made by the patient four times a day at 7:00 a.m., 11:00 a.m., 3:00 p.m., and 7:00 p.m. Use of rescue hydromorphone also was recorded by the patient.

RESULTS

Forty-five patients completed the study (26 women, 19 men; mean age, 57.1 +/- 13.6 years) and received a mean daily dose of 76 +/- 133 mg (range, 6-768 mg). There were no significant differences between controlled release hydromorphone and immediate release hydromorphone in overall VAS pain intensity scores (19 +/- 14 vs. 20 +/- 14 mm), ordinal pain intensity scores (1.2 +/- 0.8 vs. 1.2 +/- 0.8) and pain scores by day of treatment or time of day. The daily rescue analgesic consumption during controlled release hydromorphone and immediate release hydromorphone did not differ significantly overall (1.1 +/- 1.1 vs. 1.0 +/- 1.1 doses per day) or with respect to time of day. There were no significant differences in overall VAS sedation scores (18 +/- 18 mm vs. 19 +/- 18 mm) and in overall mean VAS nausea scores (12 +/- 15 mm vs. 11 +/- 14 mm) between controlled release hydromorphone and immediate release hydromorphone.

CONCLUSIONS

Controlled release hydromorphone administered every 12 hours is as effective as immediate release hydromorphone administered every 4 hours in the management of patients with chronic severe cancer pain. The benefits of controlled release hydromorphone lie in the convenience of its capsule formulation, which can be sprinkled on soft food, and its 12-hour duration of action, which allows patients uninterrupted sleep and improved compliance.