Pain in ovarian cancer patients. Prevalence, characteristics, and associated symptoms

BACKGROUND

The prevalence, characteristics, and impact of pain and other symptoms have not been studied systematically in women with ovarian cancer. Anecdotally, pain has been associated with the onset of the disease and is a common problem among those with advanced cancer; symptoms other than pain appear to be highly prevalent. Given the profound influence of pain and other symptoms on quality of life, the evaluation of these phenomena could provide data relevant to the clinical management of these patients and advance quality of life research in the area of symptom assessment.

METHODS

Questionnaires were completed by 111 inpatients and 40 outpatients with ovarian cancer who were undergoing treatment at a cancer center. Measures included a comprehensive pain questionnaire; the Rand Mental Health Inventory, Functional Living Index--Cancer; and the Memorial Symptom Assessment Scale.

RESULTS

The sample (N = 151) represented 74% of the eligible patients. The median age was 55 years (range, 23-86), 82% had Stage III or IV disease at presentation, and 69% had active disease at the time of the survey. Pain, fatigue, and psychologic distress were the most prevalent symptoms. Sixty-two percent (N = 94) described a pain syndrome that preceded the onset or recurrence of the disease, and 42% (N = 63) reported "persistent or frequent pain" during the preceding 2 weeks. The latter pain had a median duration of 2 weeks (range, less than 1 to 756 weeks) and usually was in the abdominopelvic region (80%), frequent or almost constant (66%), and moderate to severe. Most patients reported moderate or greater pain-related interference with various aspects of function, particularly activity (68%), mood (62%), work (62%), and overall enjoyment of life (61%). Performance status, inpatient status, and unmarried status were significant predictors of pain presence or intensity, and both performance status and extent of tumor were significant predictors of pain interference with function.

CONCLUSIONS

Among those with ovarian cancer, greater than 40% experienced pain that substantially undetermined function in one half to two thirds of these patients. Impaired performance status is associated most strongly with pain. The onset or recurrence of disease often is heralded by a stereotypic pain syndrome.

Opioid responsiveness of cancer pain syndromes caused by neuropathic or nociceptive mechanisms: a combined analysis of controlled, single-dose studies

We performed a combined analysis of the results from four controlled single-dose relative-potency studies to assess the impact of inferred pain mechanism on the response to an opioid drug. A total of 168 patients received 474 administrations of either morphine or heroin, and we assessed the analgesic response during a 6-hour period with visual analog scales. We summarized this as a total pain relief (TOTPAR) score. Two experienced pain clinicians reviewed information about pain characteristics and designated each case according to the inferred pain mechanism (neuropathic, nociceptive, or mixed) and the degree of confidence in the inferred mechanism (definite versus probable/possible). They grouped the cases as follows: nociceptive pain only (n = 205), neuropathic pain only (n = 49), and mixed (n = 220). We compared pain relief achieved by patients with different mechanisms, with TOTPAR adjusted for significant covariates (duration of prior opioid administration, doses of opioid administered in the previous 48 hours, pain intensity at the start of the study, BUN:creatinine ratio, and dose of administered opioid). The adjusted mean TOTPAR score of the group with any neuropathic pain was significantly lower than that of the group with nociceptive pain only (26.1 versus 20.4, p = 0.02). The score of the group with definite nociceptive pain alone (adjusted mean TOTPAR = 28.0) was significantly higher than scores of the groups with possible/probable nociceptive pain (TOTPAR = 19.9), mixed mechanisms (TOTPAR = 20.2), definite neuropathic pain alone (TOTPAR = 20.6), and possible/probable neuropathic pain alone (TOTPAR = 22.9).(ABSTRACT TRUNCATED AT 250 WORDS)

Current approaches to the management of cancer pain: a review

Pain, which is among the most prevalent symptoms experienced by cancer patients, can be effectively treated. Patient assessment, the use of anticancer therapies and systemically administered non-opioid and opioid analgesics are pivotal. Practical aspects of opioid pharmacology include both drug selection, methods of analgesic administration: selection of the appropriate route, dose titration, and an understanding of the management of side effects. Specific approaches for the management of patients unable to attain an acceptable balance between relief and side effects of opioids are described. These comprise non-invasive interventions, including the use of adjuvant analgesics, psychological therapies and physiatric techniques, and invasive interventions, such as the use of intraspinal opioids, neural blockade and neuroablative techniques. Finally, the use of sedation in the management of patients with pain that is refractory to other interventions is addressed. This approach can provide adequate relief to the vast majority of patients, most of whom will respond to systemic pharmacotherapy alone. Patients with refractory pain should have access to specialists in pain management or palliative medicine to address these difficult problems.

Neurologic pain syndromes in cancer patients

Painful neurological syndromes in cancer patients require comprehensive clinical assessment for their accurate diagnosis. Early diagnosis of the painful neurological syndromes in cancer patients allows the clinician to target his therapy toward preventing escalating pain, disability, and further neurological morbidity. Active rehabilitation is critically important in the management of these patients with neurological pain syndromes. Rehabilitation helps prevent further pain due to the development of secondary problems of immobility or disuse, helps the individual patient achieve his maximal level of functioning and helps each patient adapt to his/her neurological deficits.

Opioids

The major clinical uses for opioids are to control pain, suppress cough, and to treat diarrhea. These drugs, however, have the potential for abuse. It is postulated that the significant mood-altering effects of opioids combined with their pharmacology, in which tolerance and physical and psychological dependence occur, account for their abuse liability. A classification of the groups of patients that commonly present with complications of opioid use is reviewed briefly before discussing the clinical pharmacology of the opioids and their acute and toxic effects.

Transdermal fentanyl for cancer pain. Repeated dose pharmacokinetics

BACKGROUND

The transdermal therapeutic system (fentanyl), or TTS(fentanyl), continuously delivers fentanyl for up to 72 h. The transdermal therapeutic system (fentanyl)-100 delivers approximately 100 micrograms/h. The repeated dose pharmacokinetics of this drug using the recommended dosing interval have not been evaluated previously and were determined in the present study.

METHODS

Blood samples were obtained from ten opioid-tolerant cancer patients who received five applications of TTS(fentanyl) at 72-h intervals. A sample of venous blood was taken before each dose; multiple samples were taken during and after the fifth application. A gas chromatographic/mass spectrometry method was used to assay fentanyl (limit of detection 0.2 ng/ml).

RESULTS

For the fifth dose, the mean (SD) maximum concentration was 2.6 (1.3) ng/ml and the mean (SD) area under the serum fentanyl concentration-time curve (0-72 h) was 116.9 (59.9). Following removal of the system, the mean (SD) apparent half-life was 21.9 (8.9) h. There were no differences among the serum fentanyl concentrations measured before the second through fifth doses. Fentanyl absorption was 47% complete at 24 h, 88% complete at 48 h, and 94% complete at 72 h. The mean (SD) dose delivered during the 72-h period was 4.3 (1.1) mg. A first-dose trough concentration predicted from fifth-dose kinetics and the actual first-dose trough concentration were very similar. Adverse effects ascribed to the transdermal system were minimal.

CONCLUSIONS

These results suggest that steady-state serum concentrations are approached by the second dose of TTS(fentanyl) and that the kinetics are stable with repeated dosing. The apparent half-life following system removal is relatively long, indicating ongoing absorption from a subcutaneous depot.

Central pain from cerebral abscess: thalamic syndrome in AIDS patients with toxoplasmosis

We describe two patients with acquired immunodeficiency syndrome (AIDS) who developed classic thalamic syndrome (TS) due to Toxoplasma abscesses in the thalamic region. Treatment with amitriptyline provided substantial relief in both patients. Postmortem examination in one case revealed a lesion in the internal capsule and thalamic reticular nucleus. These observations indicate that (1) TS can result from an isolated lesion in the internal capsule and reticular nucleus of the thalamus, (2) cerebral abscess can cause classic TS, (3) central pain can be added to the many pain syndromes that afflict AIDS patients, and (4) an analgesic response to amitriptyline is possible in these patients.

The metabolite morphine-6-glucuronide contributes to the analgesia produced by morphine infusion in patients with pain and normal renal function

Morphine-6-glucuronide is a metabolite of morphine that binds to the opioid receptor and is analgesic in animals and humans. Although accumulation of morphine-6-glucuronide in patients with renal insufficiency has been implicated in morphine toxicity, the contribution of the metabolite to morphine analgesia in patients with normal renal function has not been established. To evaluate this contribution, we repeatedly sampled blood and assessed effects during and after a loading infusion with morphine (mean duration, 168 minutes) in 14 patients with chronic pain, all of whom had normal serum creatinine levels. Plasma concentrations of morphine and morphine-6-glucuronide were assayed by use of high performance liquid chromatography with electrochemical detection. Patients were divided into three groups on the basis of the molar concentration ratio of morphine-6-glucuronide:morphine from the start of the infusion until 240 minutes later: Group 1 (n = 5) had a mean ratio greater than or equal to 0.7:1; group 2 (n = 4) had a mean ratio less than 0.7:1 but greater than or equal to 0.4:1; and group 3 (n = 5) had a mean ratio less than 0.4:1. Time-effect plots revealed that average and peak relief were greater in group 1 than group 2 and greater in group 2 than group 3. For all patients, mean morphine-6-glucuronide:morphine ratio throughout the study was significantly correlated with mean pain relief (r = 0.611, p less than 0.02). These data suggest that morphine-6-glucuronide contributes to morphine analgesia in patients with normal renal function. The role of the metabolite should be considered when morphine is used clinically.

Chronic morphine therapy for cancer pain: plasma and cerebrospinal fluid morphine and morphine-6-glucuronide concentrations

Morphine-6-glucuronide (M-6-G) is an active metabolite that may contribute to the clinical effects produced by systemic administration of morphine. To help clarify the extent to which M-6-G may cross the blood-brain barrier and exert effects, we employed high-performance liquid chromatography with electrochemical detection to measure the concentrations of M-6-G and morphine in the plasma and either ventricular (three patients) or lumbar (eight patients) CSF of cancer patients receiving chronic morphine therapy. The mean ratio of morphine in ventricular CSF:morphine in plasma was 0.71; the same ratio for M-6-G was only 0.077. The average molar ratio of M-6-G: morphine in ventricular CSF was 0.207, and the average molar ratio in plasma was 1.89. Although sampling problems render the lumbar CSF results less reliable, they were very similar. Thus, plasma contained approximately twice as much M-6-G as morphine, whereas CSF contained only one-fifth to one-third as much. These data confirm that M-6-G in plasma is distributed into CSF, but to a far lesser extent than morphine. They help explain animal data demonstrating much higher potency of M-6-G on administration into CSF than systemic administration and indicate that the degree to which M-6-G contributes to morphine effects in humans remains an unresolved question.

The relationship of pain and symptom management to patient requests for physician-assisted suicide

Uncontrolled pain and multiple adverse symptoms compel some cancer patients with advanced disease to consider suicide or to request physician-assisted suicide as their only option. Any debate that focuses on the options to terminate life in patients with advanced disease must give adequate consideration to the existing level of care for patients with these distressing symptoms. Numerous studies have described the educational, attitudinal, and legislative barriers that exist and prevent patients from receiving acceptable pain and symptom management during their illness. Lack of knowledge about the use of analgesics, coupled with the lack of sophistication in diagnosing and treating the psychological complications of cancer, are examples of such educational barriers. Existing continuing care programs, like hospice, that manage symptoms in patients with far-advanced disease are currently insufficient to meet the needs of this large population. We need to address the access to expert care of distressing symptoms including pain and psychological distress as well as the quality of life of this patient population before we can fully address the options for terminating life.

Chronic nausea and morphine-6-glucuronide

Morphine-6-glucuronide is an active metabolite of morphine that has analgesic properties and is measurable in the plasma and cerebrospinal fluid of patients treated with this opioid. Decreased clearance of the compound has been observed in patients with renal insufficiency, and this has been associated with an increase in the ratio of morphine-6-glucuronide to morphine. Clinical effects from accumulation of morphine-6-glucuronide have not been described with the exception of case reports in which patients with renal failure were noted to develop opioid toxicity with high plasma levels of the metabolite and low levels of the parent drug. We describe a patient who experienced chronic nausea and an episode of confusion while treated with a small, stable dose of oral morphine in the setting of mild renal insufficiency. Relatively high levels of morphine-6-glucuronide were measured and all symptoms resolved promptly as the concentration of this metabolite declined. This case provides suggestive evidence that morphine-6-glucuronide can produce clinically significant effects in patients with mild renal insufficiency.

Pharmacokinetic-pharmacodynamic relationships of methadone infusions in patients with cancer pain

To determine the relationship between changes in plasma methadone concentration and pharmacodynamic effects, plasma methadone profiles and pharmacodynamics (analgesia and sedation) were measured during and after the continuous infusion of methadone for 180 to 270 minutes in 15 patients with pain caused by cancer. An increase in plasma methadone concentration resulted in a rapid increase in pain relief or sedation. The estimates of values of 50% of maximum effect (Css50) for pain relief and sedation obtained with a pharmacokinetic-pharmacodynamic model varied tenfold to twentyfold among patients; the mean Css50 value for pain relief (0.359 +/- 0.158 [SD] micrograms/ml) was virtually the same as the mean Css50 value for sedation (0.336 +/- 0.205 [SD] micrograms/ml). Similarly, the mean gamma (slope function) for pain relief (4.4 +/- 3.8 [SD]) and sedation (5.8 +/- 5.4 [SD]) did not differ. Examination of hysteresis plots of data obtained during the infusion and for 4 to 5 hours after cessation of the infusion revealed a very rapid equilibration between plasma methadone values and the sites mediating pain relief. There was no indication of the development of tolerance to the pharmacodynamic effects of methadone during the study. This report describes a method for quantitating the pharmacokinetic-pharmacodynamic relationships of the desirable and undesirable effects of opioid analgesics.

Character of terminal illness in the advanced cancer patient: pain and other symptoms during the last four weeks of life

There is a great variability among advanced cancer patients in the experience of symptoms and their impact on life's activities. A subgroup of difficult patients particularly tax the clinical skills and compassion of practitioners. Although the need for information about these patients is evident, their characteristics have not been explored heretofore. We describe our experience with such patients, a group referred to the Supportive Care Program of the Pain Service at Memorial Sloan-Kettering Cancer Center. Prevalence of pain and other symptoms, patterns of opioid use and routes of drug administration, and the prevalence of suicidal ideation and requests for euthanasia are discussed.

Neurologic pain syndromes in patients with cancer

One third of cancer patients in active therapy and two thirds of patients with far-advanced disease have significant pain. A series of specific neurologic pain syndromes occur in this population and are unique to this pain population. Early diagnosis and treatment are critical to prevent irreversible neurologic damage and chronic neuropathic pain.

Cancer pain management with a controlled-release oral morphine preparation

An open-label pilot study was conducted to assess the efficacy and acceptability of a controlled-release oral morphine formulation, MS Contin tablets, when administered "by the clock" two to three times daily as a substitute for opioids given on request to patients with pain caused by advanced cancer. Initially, four-hourly does of standard "immediate-release" oral morphine sulfate tablets were substituted for the patients' prior analgesic medication and titrated to individual needs. Forty of the 47 patients enrolled in the study were subsequently switched to an eight-hourly MS Contin regimen (three patients became too ill to continue the study, and four left the study during the immediate-release titration phase because of adverse reactions that may have been drug related). Small "rescue" doses of standard oral morphine were available to the patients, but they were taken infrequently. Twenty-one of the 37 patients maintained on the eight-hourly schedule consented to be treated with, and were subsequently stabilized on, MS Contin administered every 12 hr, with a reduction of over 20% in their average daily morphine dose. Most of the patients rated the controlled-release medication superior to the standard oral morphine tablets in terms of both convenience and adequacy of relief.

Guidelines for use of controlled-release oral morphine in cancer pain management. Correlation with clinical experience

An open study of 47 patients with cancer pain treated with repeated doses of a controlled-release oral morphine tablet was conducted to assess the acceptability of this drug and develop guidelines for its use. Each patient kept a detailed record of pain, analgesic intake, side effects, and other medications. A nurse observer/clinician followed these patients on a daily basis and kept similar records. Of 47 patients who began the study, 37 were successfully stabilized with standard morphine sulfate tablets and then switched to controlled-release morphine (CRM). Twenty-one patients who completed the study took CRM every 12 h, and 16 patients received a dose every 8 h. Doses of the CRM ranged from 30 mg every 12 h to 360 mg every 8 h. Less frequent doses and uninterrupted sleep were reported advantages. All of the patients completing the study chose to continue this method of pain management and extended care data were obtained from each patient poststudy through continued monitoring.

Management of pain in pancreatic cancer

Potentially useful modalities of pain control in pancreatic cancer include antitumor therapy, pharmacotherapy, celiac plexus block, splanchnic nerve block, intercostal nerve block, and psychological intervention. These modalities are often used concurrently in treating the multiple dimensions that affect pain. Although thorough assessments are lacking, preliminary data suggest that antitumor chemotherapy and radiotherapy and celiac plexus block are especially useful modalities of pain control in these patients. The optimal time in the disease course for intervention with celiac plexus block is not known. Further studies are needed to clarify the nature of pain syndromes involved and the role of the various therapeutic modalities.

Controversies in cancer pain. Medical perspectives

The treatment of pain in the patient with cancer has focused attention on a series of controversial issues involving medical, social, and moral factors. The medical factors include a lack of knowledge on the part of health care professionals regarding the rational use of opioid drugs. This is coupled with real limitations in the general understanding of the mechanisms of pain and its treatment using pharmacologic, anesthetic, and neurosurgical approaches. Several pharmacologic controversies, including the choice of drug, route and method of administration, and tolerance development and risk of substance abuse, have emerged with the use of opioids on a chronic basis in the cancer population. The social and moral implications involve the issue of who will pay for high technology pain management approaches for patients either at home or in hospice care and the ethical considerations in managing pain with opioid drugs. Carefully designed studies to assess these factors, coupled with broad educational programs, will improve the care of cancer patients in pain and expand our understanding of these important issues.

Neurologic pain syndromes in patients with cancer

Recognizing and treating the cause of pain in the patient with cancer should be the initial approach to the management of this common symptom. Careful analysis of patients with cancer and pain has led to the elucidation of common neurologic pain syndromes unique to this disease process. Pain in patients with cancer is commonly the presenting symptom of neurologic involvement. Changes in the pattern of pain or neurologic deficits should be carefully evaluated to rule out the possibility that metastatic disease may be exacerbating existing neuropathic pain. This chronic intractable pain syndrome can markedly debilitate the patient and needs an aggressive approach with drug therapy as the first-line approach.

Pain control in breast cancer. A panel discussion

Pain can be a prominent finding in breast cancer patients. It may occur in the setting of the postmastectomy period, related to the disruption of normal neural pathways or the development of lymphedema. In advanced disease, the management of pain from nerve compression or bone metastases requires special approaches. In this panel discussion, the participating physicians will discuss these topics and provide an up-to-date approach to pain control in breast cancer patients.

Pain syndromes in multiple sclerosis

To determine the prevalence and nature of pain in multiple sclerosis, we evaluated by questionnaire, interview, and chart review 159 patients residing in Middlesex County and followed in the MS Clinic at University Hospital, London, Ontario, Canada. Eighty-eight patients (55%) had either an acute or chronic pain syndrome at some time during their disease. Fifteen patients (9%) with acute pain syndromes had episodes of paroxysmal tic-like pain diagnosed in seven as trigeminal neuralgia. Chronic pain syndromes, present for a mean duration of 4.9 years, occurred in 76 patients (48%) and included dysesthetic extremity pain (29%), back pain (14%), painful leg spasms (13%), and abdominal pain (2%). MS patients with pain were similar to the pain-free group in mean age of onset (34.0 versus 31.9 years), average duration of disease (13.3 versus 12.1 years), spinal cord involvement (97% for each group), and mean rating on Kurtzke Disability Status Scale (4.2 versus 3.5). They differed in sex ratio with a higher female-to-male ratio in the pain group (3:1 versus 1.4:1). Chronic pain is a common feature of well-established MS and is usually associated with a myelopathy. Therapy must be individualized for each specific pain syndrome.

Leukemic relapse presenting as sciatic nerve involvement by chloroma (granulocytic sarcoma)

A relapse of acute nonlymphocytic leukemia in a child presented as subacute mononeuropathy involving the sciatic nerve. Surgical exploration showed a chloroma (granulocytic sarcoma) of the distal sciatic nerve, but resection and irradiation did not lead to recovery of nerve function or complete resolution of the patient's symptomatic neuropathic pain. This case represents a rare neurologic complication of what is currently an uncommon presentation for leukemic relapse, and may be the only reported case of chloromatous involvement of the peripheral nervous system (PNS) without coexisting epidural or leptomeningeal leukemia.

Vitamin A is stored as fatty acyl esters of retinol in the lacrimal gland

Many tissues which require vitamin A store the vitamin as long-chain fatty acyl esters of retinol. As part of a study designed to characterize vitamin A metabolism in the lacrimal gland, which transports retinol from blood to lacrimal gland fluid, extracts from lacrimal glands of rabbits and rats were analyzed by non-aqueous high performance liquid chromatography. Retinyl linoleate, retinyl palmitate, and retinyl stearate were identified in these extracts by their co-elution with standards, their retention time relative to retinyl palmitate, and their susceptibility to hydrolysis by saponification. Retinyl palmitate was present in rabbit lacrimal gland at 51.0 +/- 10.1 ng/g tissue. After treatment of vitamin A-deficient rabbits with orally administered [11,12-3H] retinyl acetate, the radiolabeled esters retinyl linoleate, palmitate, and stearate were extracted from the lacrimal glands. These data show that the lacrimal gland stores vitamin A as fatty acyl esters of retinol.

Sublingual absorption of selected opioid analgesics

Ongoing interest in the improvement of pain management with opioid analgesics had led to the investigation of sublingual opioid absorption. The present report determined the percent absorption of selected opioid analgesics from the oral cavity of normal subjects under conditions of controlled pH and swallowing when a 1.0 ml aliquot of the test drug was placed under the tongue for a 10-minute period. Compared with morphine sulfate at pH 6.5 (18% absorption), buprenorphine (55%), fentanyl (51%), and methadone (34%) were absorbed to a significantly greater extent (p less than 0.05), whereas levorphanol, hydromorphone, oxycodone, heroin, and the opioid antagonist naloxone were not. Overall, lipophilic drugs were better absorbed than were hydrophilic drugs. Plasma morphine concentration-time profiles indicate that the apparent sublingual bioavailability of morphine is only 9.0% +/- 11.9% (SD) of that after intramuscular administration. In the same subjects the estimated sublingual absorption was 22.4% +/- 9.2% (SD), indicating that the sublingual absorption method may overestimate apparent bioavailability. When the oral cavity was buffered to pH 8.5, methadone absorption was increased to 75%. Thus, an alkaline pH microenvironment that favors the unionized fraction of opioids increased sublingual drug absorption. Although absorption was found to be independent of drug concentration, it was contact time dependent for methadone and fentanyl but not for buprenorphine. These results indicate that although the sublingual absorption and apparent sublingual bioavailability of morphine are poor, the sublingual absorption of methadone, fentanyl, and buprenorphine under controlled conditions is relatively high.

The Memorial Pain Assessment Card. A valid instrument for the evaluation of cancer pain

Effective evaluation and treatment of cancer pain require valid and independent measurement of pain intensity, pain relief, and psychological distress. The Memorial Pain Assessment Card (MPAC) is a simple instrument designed to provide rapid evaluation of these subjective experiences. On the 8.5 by 11 inch card are printed the eight pain intensity descriptors, and three visual analog scales which measure pain intensity, pain relief, and mood. Experienced patients can complete it in less than 20 seconds. The authors administered the MPAC to 50 hospitalized cancer patients within 48 hours of referral to the Pain Service for inadequate pain control, together with standard measures: The McGill Pain Questionnaire, Profile of Mood States, Hamilton Depression Scale, and Zung Anxiety Scale. Correlational and multiple regression analyses revealed that the MPAC can distinguish pain intensity from pain relief and from general psychological distress, and it can provide multidimensional assessment that is practically equivalent to the full assessment battery. We conclude that the MPAC is valid and effective for clinical use, and recommend it for the assessment of individual patients, and as an outcome measure in clinical trials.

Pharmacokinetics and pharmacodynamics of methadone in patients with chronic pain

Concentrations of methadone in plasma, estimates of pain relief, and pupillary size were determined after a single intravenous dose (10 to 30 mg) of methadone hydrochloride to eight patients with chronic pain, five of whom had cancer. The pharmacokinetic parameter estimates reveal rapid and extensive distribution (Varea) and a slow apparent elimination half-life (t1/2) (mean Varea = 3.59 L/kg and harmonic mean t1/2 = 23 hours). The harmonic mean blood clearance is 106 ml/min, the harmonic mean renal clearance is 3.9 ml/min, the mean hepatic extraction ratio is 0.089, and plasma protein binding is 86% to 89%. These results suggest that only the free (unbound) fraction of methadone present in blood is extracted by the liver and that methadone can be classified as a low (hepatic)-extraction drug. The data were fit to a pharmacokinetic-pharmacodynamic model to obtain estimates of the steady-state plasma methadone concentration required to produce 50% of the maximum pain relief. This value varied from 0.04 to 1.13 micrograms/ml (mean = 0.29 micrograms/ml). These results indicate substantial interindividual variation in the relationship between changes in plasma methadone concentration and analgesia in patients with chronic pain receiving opioids. A pharmacokinetic-pharmacodynamic model may be useful for the individualization of analgesic dosage and therefore the optimization of pain management in patients with chronic pain.

Analgesic drug therapy in cancer pain: principles and practice

Drug therapy represents the mainstay of treatment for patients with cancer pain. Non-narcotic, narcotic, and adjuvant analgesics are the commonly used agents. The choice of a specific analgesic drug regimen is dependent on the type of pain and its severity, and the drug must be titrated to the individual needs of the patient.

Pain syndromes in patients with cancer

A series of common pain syndromes in patients with pain and cancer includes pain associated with direct tumor infiltration, pain resulting from cancer therapy, and pain unrelated to the cancer or cancer therapy. Appropriate management is dependent on their careful evaluation.

Back pain in the cancer patient: an algorithm for evaluation and management

Epidural spinal cord compression is common in patients with metastatic cancer. Back pain is usually the first symptom and may be present for months before neurologic abnormalities occur. A favorable outcome depends on early diagnosis and treatment. For the management of this problem, we propose an algorithm that begins with the treatment of patients who need emergency care and proceeds with an orderly approach to the evaluation of less urgent cases. The central elements include the criteria for myelography and the rational use of corticosteroids, radiation therapy, and surgery.

Acute herpetic and postherpetic neuralgia: clinical review and current management

The pain of acute herpes zoster (HZ) may be severe, but it is usually transitory. A minority of patients, with the elderly at particular risk, go on to develop persistent, severe, often disabling pain called postherpetic neuralgia. Though the clinical features of these conditions are well known, the pathology of PHN is poorly described and the pathogenesis of the pain in both remains conjectural. During the past 60 years, an extraordinary number of pharmacological, anesthetic, and surgical therapies have been applied in an attempt to ameliorate the symptoms of acute herpes zoster, enhance its healing, prevent its transition to postherpetic neuralgia, and treat the pain of those with this complication. Relatively few treatments have been studied in a controlled manner, and fully reliable, safe, and effective therapeutic approaches for preventing and treating postherpetic neuralgia have not yet been found. This review summarizes current information on the epidemiology, clinical features, and pathology of herpes zoster and postherpetic neuralgia, and critically examines the accumulated experience with the various treatments. Guidelines for management are suggested.

Retinol secretion by the lacrimal gland

In order to determine the source of the retinol which has been identified in the tear fluid, the lacrimal gland ducts of rabbits and rats were cannulated and the collected lacrimal gland fluid was analyzed by high performance liquid chromatography. Retinol was identified in the lacrimal gland fluid of rabbits and rats, and it is concluded that the lacrimal gland is the source of retinol in the tears. Dose-response studies show that intravenously administered pilocarpine and intra-arterial acetylcholine stimulate secretion of retinol by the lacrimal gland. Intravenous administration of vasoactive intestinal peptide (VIP) also stimulates retinol secretion in a dose-response manner. These observations are similar to the effects of cholinergic drugs and VIP on protein secretion by the lacrimal gland.

Cerebrospinal fluid pharmacokinetics of intrathecal morphine sulfate and D-Ala2-D-Leu5-enkephalin

Using an implantable pump system to deliver drugs and sample cerebrospinal fluid (CSF), we assessed rostral redistribution and systemic uptake after intrathecal bolus injection and steady-state infusion of morphine sulfate and the opioid peptide D-Ala2-D-Leu5-enkephalin (DADL) in two patients. Following bolus injection, the mean CSF elimination half-lives for morphine sulfate and DADL were 94 and 115 minutes, respectively. With the catheter tip at L2, the ratio of lumbar to cisternal (L/C) concentrations of morphine sulfate was about 7:1, and with the catheter tip at T10, the L/C ratios of morphine sulfate and DADL were approximately 2:1, indicating that this ratio is dependent in part on the level of intrathecal drug administration. CSF levels of morphine sulfate at steady state were three orders of magnitude higher than those in plasma. The CSF pharmacokinetics of morphine sulfate and DADL are similar, with supraspinal redistribution of these opioids via the CSF likely playing an important role in the generation of analgesia and central nervous system side effects.

The treatment of pain in the patient with cancer

Pain is one of the most feared consequences of cancer. Control of pain from cancer should be possible with the approaches discussed above. Changing attitudes toward the effective use of narcotic analgesics, the development of novel routes and methods of administration, and a clinical approach based on scientific principles and humane care offer the promise of improved management of pain in patients with cancer.

I.v. infusion of opioids for cancer pain: clinical review and guidelines for use

To assess the safety, efficacy, and use of continuous iv infusion (CI) of opioids for cancer pain, we reviewed the clinical experience of 36 patients who received 46 CIs. CI was always preceded by a period of repetitive dosing of opioids. Morphine was used in 36 CIs, methadone in four, hydromorphone in four, oxymorphone in one, and levorphanol in one. Mean doses during CI were the morphine equivalent of 17 mg/hour (range, 0.7-100) at the start, 69 mg/hour (range, 4-480) at the maximum, and 52 mg/hour (range, 1-480) at termination. Pain relief was acceptable during 28 CIs, unacceptable during 17, and unknown during one. There were few toxic effects other than sedation. Twenty-five patients died, 12 resumed im or oral opioids, six continued CI with a different opioid (yielding analgesia in two), and outcome was undetermined in three. This review suggests that (a) CI is safe, (b) analgesia may require rapid escalation of infusion rates, (c) patient response varies and lack of acceptable analgesia may occur in up to one-third, (d) ineffective CI with one drug may be followed by success with another, (e) CI should be preceded by a period of repetitive iv boluses with the same drug, and (f) guidelines can be developed which incorporate pharmacokinetic principles.

The efficacy of retinoic acid ointment for treatment of xerophthalmia and corneal epithelial wounds

In previous studies of topical application of retinoic acid to the eye, retinoic acid in an oil vehicle has been used. An all-trans-retinoic acid (Tretinoin, USP) formulation in a petrolatum-based ophthalmic ointment vehicle has now been developed which is chemically stable for at least one year. The ointment is effective at retinoic acid concentrations of 0.01-0.1% in reversing corneal keratinization in vitamin A-deficient, xerophthalmic rabbits. At 0.1% it also stimulates the healing rate of corneal epithelial wounds in rabbits and monkeys. Retinoic acid ointment may prove to be valuable clinically in the treatment of xerophthalmia, corneal epithelial erosions, and related ocular surface abnormalities.

The treatment of cancer pain

Pain is one of the most feared consequences of cancer. Control of pain from cancer should be possible with the approaches discussed above. Changing attitudes toward the effective use of narcotic analgesics, the development of novel routes and methods of administration, and a clinical approach based on scientific principles and humane care offer the promise of improved management of pain in patients with cancer.

Pain measurement: an overview

The practice and theoretical basis of pain measurement is reviewed and critically examined in the areas of animal research, human subjects laboratory investigation and clinical study. The advantages and limitations of both physiological and behavioral methods are discussed in each area, and subjective report procedures are evaluated in human laboratory and clinical areas. The need for procedures that bridge these areas is emphasized and specific issues are identified. Progress in the technology of pain measurement over recent decades is reviewed and directions for future work are suggested.

The natural history of lumbosacral plexopathy in cancer

We studied 85 cancer patients with lumbosacral plexopathy and documented pelvic tumor by CT or biopsy. Three clinical syndromes were delineated: lower (L4-S1), 51%; upper (L1-L4), 31%; and pan-plexopathy (L1-S3), 18%. Seventy percent of patients had the insidious onset of pelvic or radicular leg pain, followed weeks to months later by sensory symptoms and weakness. The quintet of leg pain, weakness, edema, rectal mass, and hydronephrosis suggests plexopathy due to cancer. CT showed pelvic tumor in 96%. On myelography, epidural extension, usually below the conus medullaris, was seen in 45%. With treatment, only 28% of patients had objective responses on CT and 17% on examination.

An anterior surgical approach to the upper thoracic vertebrae

Of the various anterior surgical approaches to the spine, exposure of the upper two thoracic vertebrae remains the most challenging. An operative approach to this region is described. The major features include resection of a portion of the clavicle and the manubrium sterni. Following resection of the tumor and involved vertebra, anterior fusion is performed using the clavicle as a strut graft. Immediate stabilization may also be achieved with methyl methacrylate replacement of the vertebral bodies. The operation is well tolerated, and requires minimal postoperative immobilization. The clinical presentation, radiological features, and results of treatment in a series of seven patients operated on during a 2-year period are presented.