Absolute bioavailability of hydromorphone after peroral and rectal administration in humans: saliva/plasma ratio and clinical effects

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.

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.

Prescription Opioids. VI. Metabolism and Excretion of Hydromorphone in Urine Following Controlled Single-Dose Administration

Hydromorphone (HM), a prescription opioid and metabolite of morphine and hydrocodone, has been included in proposed revisions to the Mandatory Guidelines for Federal Workplace Drug Testing Programs. This study characterized the time course of HM in hydrolyzed and non-hydrolyzed urine specimens. Twelve healthy subjects were administered a single 8 mg controlled-release HM dose, followed by periodic collection of pooled urine specimens for 54 h following administration. Analysis of total and free HM was conducted by liquid chromatography tandem mass spectrometry at a 50 ng/mL limit of quantitation. Detection periods were determined over a range of thresholds from 50 to 2,000 ng/mL. HM was detected in 85.3% and 47.6% of hydrolyzed and non-hydrolyzed post-dose specimens, respectively. Initial detection of total HM was frequently observed in the first 4-6 h following dosing. The period of detection at the 50 ng/mL threshold averaged 52.3 h for total HM and 38.0 h for free HM. These data support that HM detection is optimized by using low thresholds (50-100 ng/mL) and including conjugated HM in the analysis.

Saliva versus Plasma for Pharmacokinetic and Pharmacodynamic Studies of Fentanyl in Patients with Cancer

PURPOSE

Fentanyl is widely used to relieve cancer pain. However there is great interpatient variation in the dose required to relieve pain and little knowledge about the pharmacokinetic and pharmacodynamic (PK/PD) relationship of fentanyl and pain control. Patients with cancer are fragile and there is reluctance on the part of health professionals to take multiple plasma samples for PK/PD studies. The relationship between plasma and saliva fentanyl concentrations was investigated to determine whether saliva could be a valid substitute for plasma in PK/PD studies.

METHODS

One hundred sixty-three paired plasma and saliva samples were collected from 56 patients prescribed transdermal fentanyl (Durogesic, Janssen-Cilag Pty Limited, NSW, Australia) at varying doses (12-200 µg/h). Pain scores were recorded at the time of sampling. Fentanyl and norfentanyl concentrations in plasma and saliva were quantified using HPLC-MS/MS.

FINDINGS

Saliva concentrations of fentanyl (mean = 4.84 μg/L) were much higher than paired plasma concentrations of fentanyl (mean = 0.877 μg/L). Both plasma and saliva mean concentrations of fentanyl were well correlated with dose with considerable interpatient variation at each dose. The relationship between fentanyl and norfentanyl concentrations was poor in both plasma and saliva. No correlation was observed between fentanyl concentration in plasma and saliva (r(2) = 0.3743) or free fentanyl in plasma and total saliva concentrations (r(2) = 0.1374). Pain scores and fentanyl concentration in either of the matrices were also not correlated.

IMPLICATIONS

No predictive correlation was observed between plasma and saliva fentanyl concentration. However the detection of higher fentanyl concentrations in saliva than plasma, with a good correlation to dose, may allow saliva to be used as an alternative to plasma in PK/PD studies of fentanyl in patients with cancer.

Development, validation and application of an HPLC-MS/MS method for the determination of fentanyl and nor-fentanyl in human plasma and saliva

Monitoring fentanyl concentration in saliva and plasma may be useful in pharmacokinetic/pharmacodynamic studies. Salivettes(®) have been used widely for collecting saliva samples. However due to its lipophilicity, fentanyl adsorbs to the cotton dental bud (CDB) used in this device. Furthermore, due to dry mouth being a common adverse effect seen in patients treated with opioids, obtaining enough saliva for analysis is often a challenge. Hence, a simple simultaneous method to quantify fentanyl and its metabolite in both human plasma and saliva was developed and validated. A novel extraction method was also developed and validated to recover fentanyl in saliva directly from the CDB. This extraction method utilises acetonitrile to recover the fentanyl directly from the CDB rather than recovery by centrifugation, which is not always possible. Reverse phase chromatographic separation was performed on a Shimadzu LC 20A HPLC system using gradient elution. The electrospray ion source (ESI) was operated in positive ion mode using an Applied Biosystems API 3200 LC/MS/MS as detector. Deuterated fentanyl (D5) and nor-fentanyl (D5) were used as internal standards (IS). The retention times for fentanyl and nor-fentanyl were 3.70 min and 3.20 min respectively. The lower limit of quantitation (LLOQ) was determined to be 0.030 μg/L in plasma and 0.045 in saliva for fentanyl and nor-fentanyl. Acceptable linearity for fentanyl and nor-fentanyl in both plasma and saliva was demonstrated from 0.02 to 10 μg/L (R(2) 0.9988-0.9994). Accuracy for fentanyl and nor-fentanyl in both plasma and saliva samples was between 96% and 108%. Total imprecision expressed as the co-efficient of variation was between 1.0 and 15.5% for both analytes in both matrices. The validated method was applied successfully in 11 paired plasma and saliva samples obtained from patients with cancer pain receiving transdermal fentanyl (Duragesic(®)) at doses from 25 μg to 100 μg.

Interpretation of oral fluid tests for drugs of abuse

Oral fluid testing for drugs of abuse offers significant advantages over urine as a test matrix. Collection can be performed under direct observation with reduced risk of adulteration and substitution. Drugs generally appear in oral fluid by passive diffusion from blood, but also may be deposited in the oral cavity during oral, smoked, and intranasal administration. Drug metabolites also can be detected in oral fluid. Unlike urine testing, there may be a close correspondence between drug and metabolite concentrations in oral fluid and in blood. Interpretation of oral fluid results for drugs of abuse should be an iterative process whereby one considers the test results in the context of program requirements and a broad scientific knowledge of the many factors involved in determining test outcome. This review delineates many of the chemical and metabolic processes involved in the disposition of drugs and metabolites in oral fluid that are important to the appropriate interpretation of oral fluid tests. Chemical, metabolic, kinetic, and analytic parameters are summarized for selected drugs of abuse, and general guidelines are offered for understanding the significance of oral fluid tests.

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.

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.

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.

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.

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.

Testing for drugs of abuse in saliva and sweat

The detection of marijuana, cocaine, opiates, amphetamines, benzodiazepines, barbiturates, PCP, alcohol and nicotine in saliva and sweat is reviewed, with emphasis on forensic applications. The short window of detection and lower levels of drugs present compared to levels found in urine limits the applications of sweat and saliva screening for drug use determination. However, these matrices may be applicable for use in driving while intoxicated and surveying populations for illicit drug use. Although not an illicit drug, the detection of ethanol is reviewed because of its importance in driving under the influence. Only with alcohol may saliva be used to estimate blood levels and the degree of impairment because of the problems with oral contamination and drug concentrations varying depending upon how the saliva is obtained. The detection of nicotine and cotinine (from smoking tobacco) is also covered because of its use in life insurance screening and surveying for passive exposure.

An assessment of the routes of incorporation of opiates into beard hair after a single oral dose of codeine

The time course of appearance of immunoreactive opiates was monitored in saliva, sweat, and beard hair in six healthy whites who were not opiate users after oral administration of 60 mg of codeine phosphate. The opiate concentration in saliva peaked within 30 min of drug administration and returned to near the predose level within 24 h. Ninety-one percent of the total secretion of opiates in sweat was collected by the skin-collection patch worn during the first 24 h after drug administration. Detectable material was also present in sweat patches on the following 2 days. Opiates were detected in extracts of alkali digests of beard hair in all subjects on the day after drug administration. Hair concentration peaked on day 3 after dosing and then decreased continuously until day 8. From day 8 until the end of the experiment on day 14, beard hair contained opiate concentrations significantly greater than the predose level. From comparison with cotinine pharmacokinetics, it is proposed that an early and the largest transfer of opiates into beard hair is through sweat. Transfer during hair growth is secondary and of comparable importance to a newly identified contribution of long duration that may involve transfer from storage depots within skin.

Management of chronic pain. Part I

Chronic pain is associated with substantial psychosocial and economic stress, coupled with functional loss and various levels of vocational dysfunction. The role of a pain center is to focus on chronic pain in a multidisciplinary, comprehensive manner, providing the patient with the most effective opportunity to manage his or her chronic disease syndrome. This article focuses on methods to manage many types of chronic pain and describes a broad range of pharmacologic and nonpharmacologic interventions and options available to the patient. Part I of this two-part monograph describes pharmacotherapeutic interventions and regional nerve blocks. Part II focuses on psychologic assessment and treatment and physical therapy. A multimodal management strategy offers patients the greatest improvement potential for specific chronic pain syndromes. Cognitive and behavioral therapies and physical therapies are described. This combination of therapies may provide patients with the skills and knowledge needed to increase their sense of control over pain. The integration of appropriate pharmacotherapeutic regimens, neural blockades, physical therapy, and psychologic techniques maximizes a patient's effectiveness in dealing with chronic pain. Three case studies are presented in Part II.

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.

Saliva testing for drugs of abuse

Saliva testing for drugs of abuse can provide both qualitative and quantitative information on the drug status of an individual undergoing testing. Self-administration by the oral, intranasal, and smoking routes often produces "shallow depots" of drug that contaminate the oral cavity. This depot produces elevated drug concentrations that can be detected for several hours. Thereafter, saliva drug concentrations generally reflect the free fraction of drug in blood. Also, many drugs are weak bases and saliva concentrations may be highly dependent upon pH conditions. These factors lead to highly variable S/P ratios for many of the drugs of abuse. Table 3 provides a compilation of experimental and theoretical S/P (total) ratios determined for drugs of abuse. Estimations of the theoretical S/P (total) ratios for acidic and basic drugs were based on the Henderson-Hasselbalch equation. Saliva pH was assumed to be 6.8 unless reported otherwise by the investigators. Generally, there was a high correlation of saliva drug concentrations with plasma, especially when oral contamination was eliminated. Assay methodology varied considerably, indicating that saliva assays could be readily developed from existing methodology. There are many potential applications for saliva testing for drugs of abuse. Table 4 lists several general areas in which information from saliva testing would be useful. Clearly, saliva drug tests can reveal the presence of a pharmacologically active drug in an individual at the time of testing. Significant correlations have been found between saliva concentrations of drugs of abuse and behavioral and physiological effects. Results indicate that saliva testing can provide valuable information in diagnostics, treatment, and forensic investigations of individuals suspected of drug abuse. It is expected that saliva testing for drugs of abuse will develop over the next decade into a mature science with substantial new applications.

Pharmacokinetics of rectal drug administration, Part II. Clinical applications of peripherally acting drugs, and conclusions

Part I of this article, which appeared in the previous issue of the Journal, covered general considerations, the physiology of the rectum, spreading of drugs into the colon, rectal absorption, partial avoidance of first-pass elimination, rate-controlled rectal delivery of drugs, irritation of the rectal mucosa and clinical applications of rectal administration, and discussed centrally acting drugs. In Part II, this discussion is extended to drugs which act peripherally and to methods of enhancing rectal drug absorption. The overall summary appeared in Part I.

Review of the rectal use of opioids

The rectal route for the administration of opioid analgesics is often forgotten by physicians seeking alternatives to the oral route. This article reviews the physiology of rectal drug absorption and such data as exists on the different opioids that have been administered by this route. Conventional fatty-based suppositories have a place in the management of chronic pain but the variability in dissolution and drug absorption limit their usefulness. Recently, sustained release vehicles have become available that offer the prospect of the attainment of steady analgesic drug concentrations with once or twice daily dosing. Early studies with the morphine hydrogel suppository suggest that it may be capable of fulfilling this prospect. Their inherent safety, as dose-dumping is impossible, will make them suitable for use in the home.