Rectal methadone in cancer patients with pain. A preliminary clinical and pharmacokinetic study

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.

Methadone for Pain Management: A Pharmacotherapeutic Review

Methadone is increasingly being used for its analgesic properties. Despite the increasing popularity, many healthcare providers are not familiar with methadone's complex pharmacology and best practices surrounding its use. The purpose of this narrative review article is to discuss the pharmacology of methadone, the evidence surrounding methadone's use in acute pain management and both chronic cancer and non-cancer pain settings, as well as highlight pertinent safety, monitoring, and opioid rotation considerations. Methadone has a unique mechanism of action when compared with all other opioids and for this reason methadone has come to hold a niche role in the management of opioid-induced hyperalgesia and central sensitization. Understanding of the mechanisms of variability in methadone disposition and drug interactions has evolved over the years, with the latest evidence revealing that CYP 2B6 is the major determinant of methadone elimination and plays a key role in methadone-related drug interactions. From an acute pain perspective, most studies evaluating the use of intraoperative intravenous methadone have reported lower pain scores and post-operative opioid requirements. Oral methadone is predominantly used as a second-line opioid treatment for select chronic pain conditions. As a result, several oral morphine to oral methadone conversion ratios have been proposed, as have methods in which to rotate to methadone. From an efficacy standpoint, limited literature exists regarding the effectiveness of methadone in the chronic pain setting with most of the available efficacy data pertaining to methadone's use in the treatment of cancer pain. Many of the prospective studies that exist feature low participant numbers. Few clinical trials investigating the role of methadone as an analgesic treatment are currently underway. The complicated pharmacokinetic properties of methadone and risks of harm associated with this drug highlight how critically important it is that healthcare providers understand these features before prescribing/dispensing methadone. Particular caution is required when converting patients from other opioids to methadone and for this reason only experienced healthcare providers should undertake such a task. Further randomized trials with larger sample sizes are needed to better define the effective and safe use of methadone for pain management.

Pharmacological Treatment of Cancer Pain: Alternative Routes of Opioid Administration

Cancer-related pain is present in 51% of patients at various stages of the disease, and the incidence increases up to 74% in advanced and terminal stages. The World Health Organization proposed and issued very simple guidelines for the pharmacologic treatment of cancer-related pain. According to the guidelines, opioid analgesics are the mainstay of analgesic therapy, and the first choice for drug administration is considered to be the oral route. However, in some clinical situations, the oral route is not feasible, and analgesic drugs consequently have to be administered via an alternative route. For example, this is the case when the patient presents vomiting, bowel obstruction, severe dysphagia, mental confusion and when the opioid dose has to be increased drastically in order to achieve adequate pain control. This review of the literature is aimed at describing the indications, the limits and the main aspects of the pharmacokinetics and pharmacodynamics relative to the alternative routes of administration of opioids most commonly used in clinical practice. Sublingual, rectal, subcutaneous, intravenous, transdermal and spinal administration routes are examined.

Is levorphanol a better option than methadone?

BACKGROUND

Methadone has been a stalwart pharmacologic option for the management of opioid drug dependence for many years. It substitutes for opioid agonists and possesses certain pharmacokinetic properties that confer characteristics preferable to those of other opioids for this application. Methadone is likewise used as an option for the treatment of pain, particularly chronic pain. It has a spectrum of pharmacodynamic activity, including contributions from non-opioid components, that translates to its specific clinical attributes as an analgesic. Unfortunately, basic science studies and accumulated clinical experience with methadone have revealed some undesirable, and even worrisome, features, including issues of safety. The benefit/risk ratio of methadone might be acceptable if there was no better alternative, but neither its pharmacokinetic nor pharmacodynamic properties are unique to methadone.

OBJECTIVE

We review the basic and clinical pharmacology of methadone and suggest that levorphanol should receive attention as a possible alternative.

CONCLUSION

Unlike methadone, levorphanol is a more potent NMDA antagonist, possesses a higher affinity for DOR and KOR, has a shorter plasma half-life yet longer duration of action, has no CYP450 interactions or QTc prolongation risk, can be a viable option in the elderly, palliative care, and SCI patients, requires little to no need for co-administration of adjuvant analgesics, and has potentially a lower risk of drug-related Emergency Department visits compared to other opioids.

[Use of methadone in the elderly with cancer pain: a systematic review]

OBJECTIVE

To identify the clinical use of methadone as an analgesic in the management of cancer pain in elderly patients.

MATERIAL AND METHODS

We performed a systemic review of the literature on the specific use of methadone in elderly with cancer pain in MEDLINE, COCHRANE DATABASE and SCOPUS. A second search was conducted in MEDLINE to look for clinical trials and systematic review of the use of methadone in cancer pain, selecting only those in which the mean age of patients was ≥ 65 years old.

RESULTS

Four articles were obtained in the first search, and from the second 7 clinical trials, none of them specific to methadone use in elderly patients with cancer.

CONCLUSIONS

There are insufficient data on the use of methadone as an analgesic in the elderly with cancer. Given its pharmacological characteristics it must be used by trained personnel. Several recommendations are proposed for its use as an analgesic in the treatment of cancer pain in the elderly.

Methadone in cancer pain

Methadone is often considered as a second-choice drug alternative to morphine in cancer pain treatment. A lack of information regarding methadone's pharmacokinetic/pharmacodynamic relationships has contributed to limitation in its use in analgesic treatments. However, it has been recently re-evaluated in light of better knowledge of its pharmacological characteristics and wider experience. Concern about the safety of methadone therapy arising because of its long and unpredictable half-life should not deter clinicians from its appropriate use. Methadone is a very useful drug in cancer pain because of its low cost, lack of known metabolites, high oral bioavailability, rapid onset and time to peak analgesic effect, and the long duration of activity which allows for longer intervals between doses. Moreover, methadone has been demonstrated to have a high receptor reserve and to exert some NMDA receptor antagonist effect. A shift from one opioid to methadone is recommended when the side-effect/analgesic balance is unfavourable, as symmetrical patterns of cross-tolerance of opioid agonists have been demonstrated. Different approaches, including the oral PCA, have been proposed to circumvent problems related to its pharmacokinetic properties.

The role of methadone in cancer pain treatment--a review

BACKGROUND

Methadone is an opioid analgesic of step 3 of the World Health Organization (WHO) analgesic ladder.

AIM AND METHODS

To outline pharmacodynamics, pharmacokinetics, drug interactions, equianalgesic dose ratio with other opioids, dosing rules, adverse effects and methadone clinical studies in patients with cancer pain. A review of relevant literature on methadone use in cancer pain was conducted.

RESULTS

Methadone is used in opioid rotation and administered to patients with cancer pain not responsive to morphine or other strong opioids when intractable opioid adverse effects appear. Methadone is considered as the first strong opioid analgesic and in patients with renal impairment. Methadone possesses different pharmacodynamics and pharmacokinetics in comparison to other opioids. The advantages of methadone include multimode analgesic activity, high oral and rectal bioavailability, long lasting analgesia, lack of active metabolites, excretion mainly with faeces, low cost and a weak immunosuppressive effect. The disadvantages include long and changeable plasma half-life, high bound to serum proteins, metabolism through P450 system, numerous drug interactions, lack of clear equianalgesic dose ratio to other opioids, QT interval prolongation, local reactions when administered subcutaneously.

CONCLUSIONS

Methadone is an important opioid analgesic at step 3 of the WHO analgesic ladder. Future controlled studies may focus on establishment of methadone equianalgesic dose ratio with other opioids and its role as the first strong opioid in comparative studies with analgesia, adverse effects and quality of life taken into consideration.

The role of methadone in opioid rotation-a Polish experience

BACKGROUND

To assess methadone analgesia, adverse effects, and calculation method of equianalgesic doses with oral morphine.

MATERIALS AND METHODS

Methadone was administered to 21 opioid-tolerant cancer patients because of pain (numerical rating scale [NRS] > 5) on morphine (ten patients), transdermal fentanyl (TF; four patients), morphine, ketamine, and TF (one patient), tramadol (one patient), pethidine (one patient), pain with drowsiness on morphine with ketamine (three patients), and pain with nausea on morphine (one patient). Dose ratios of equivalent daily dose of oral morphine (ddom) to daily dose of oral methadone (ddomet) were 4:1 (ddom to 100 mg), 6:1 (101-300 mg), 12:1 (301-1,000 mg), and 20:1 (over 1,000 mg). Previous opioid treatment was stopped completely (stop-start approach) in 19 patients; two received methadone and other opioids. The mean ddom before switch was 812 +/- 486 mg. Methadone was administered regularly three times daily; 20 patients received oral methadone, one patient received rectal suppositories. Breakthrough pain was treated with methadone (half of regular dose), morphine, fentanyl, metamizol, ketoprofen, or ketamine.

RESULTS

Mean time of methadone treatment was 38.3 +/- 27.1 days (range 3-95 days), mean daily doses: start 48.1 +/- 19.7 mg, maximal 148.5 +/- 104.1 mg, treatment completion 131.1 +/- 104.3 mg. Good analgesia (NRS < 4) was observed in 11 patients, partial (NRS 4-5) in nine patients, and unsatisfactory (NRS > 5) in one patient. Adverse effects such as drowsiness (six patients), constipation (six patients), nausea and vomiting (two patients), sweating (two patients), and respiratory depression (one patient) the last one resolved by methadone cessation and naloxone.

CONCLUSIONS

Results confirmed high analgesic efficacy, acceptable methadone adverse event profile, safety, and effectiveness of ddom to ddomet dose calculation method.

Methadone for cancer pain

BACKGROUND

Methadone is an opioid used in the management of cancer pain. A particular role in neuropathic pain has been suggested. The quest for evidence based palliative care prompted a formal appraisal of methadone in comparison with other analgesics. This is an updated version of the original Cochrane review published in Issue 1, 2004.

OBJECTIVES

To determine effectiveness and safety of methadone analgesia in cancer pain patients.

SEARCH STRATEGY

MEDLINE, EMBASE, CancerLit, CINAHL and Cochrane databases were searched in 2002 using a strategy developed with the Cochrane Pain, Palliative and Supportive Care Group. Repeat searches were conducted in September 2006.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of methadone against active or placebo comparator in patients with cancer pain were included. Outcome measures sought were reduction in pain intensity, adverse effects, attrition, patient satisfaction and quality of life. There were no language restrictions.

DATA COLLECTION AND ANALYSIS

Eligible studies were selected with independent collaboration from a colleague. Full text was retrieved if any uncertainty about eligibility remained. Non-English texts were screened by Cochrane contacts. Quality assessment and data extraction were conducted using standardised data forms. Drug and placebo dose, titration, route and formulation were compared and detail of all outcome measures (if available) recorded.

MAIN RESULTS

This updated review includes nine RCTs (six double blinded, two crossover) with 459 recruits and 392 completing patients. All studies involved active opioid comparators (morphine, dextromoramide, pethidine, diamorphine with cocaine mixture) with different dose and titration schedules and various pain scoring scales. One study differentiated cases by pain syndrome. Few presented complete pain data sets but complete adverse events data were recorded in every study. Efficacy and tolerability were broadly similar between methadone and morphine. No useful meta-analysis has been possible.

AUTHORS' CONCLUSIONS

The updated review contains new information supporting the previous conclusions that methadone has similar analgesic efficacy to morphine. The additional study examined neuropathic and non-neuropathic pain, finding no superiority for methadone in the former group. The new study also addresses a clinically relevant concern about short term/single dose studies. Use beyond a few days may result in methadone accumulation leading to delayed onset of adverse effects. In an assessment over 28 days there was a higher rate of withdrawal due to side effects in the methadone group. This observation reinforces the advice that experienced clinicians should take responsibility for initiation and careful dose adjustment and monitoring of methadone.

Methadone for treatment of cancer pain

Methadone is a unique mu opioid agonist, which also has delta receptor affinity and properties of N-methyl-D-aspartate receptor antagonism and monoamine reuptake inhibition. It is mainly used in the setting of uncontrolled pain or dose-limiting toxicity. Caution is advised when switching to methadone, especially from high doses of previous opioid, due to its variable conversion ratio and the potential for delayed toxicity due to its long half-life. Increasing evidence of risk also exists for a prolonged QT interval and torsades de pointes with very large doses of methadone. Methadone is likely safer when used at lower doses as a first-line opioid, but its potential as such has not received enough formal evaluation. Randomized controlled trials are needed to assess the effectiveness and safety of methadone compared with other opioids and to further evaluate its role in the treatment of neuropathic pain.

Randomized double-blind, double-dummy crossover clinical trial of oral tramadol versus rectal tramadol administration in opioid-naive cancer patients with pain

Tramadol is commonly used as second step drug of the analgesic ladder. In circumstances where the oral route is unavailable, rectal administration of opioids might be a simple alternative. The aim of this study was to compare the analgesic activity and tolerability of tramadol by oral and rectal administration in a double-blind, double-dummy crossover trial. The study included 60 cancer patients with cancer pain no longer responsive to non-opioid drugs. Each patient initially received oral tramadol 50 mg (drops), followed by tramadol sustained release 100 mg orally, and placebo rectally, or tramadol 100 mg rectally and placebo orally, twice a day, in a randomized sequence, on each of 3 days. Patients were allowed to take 50 mg of oral tramadol by drops as needed (four doses per day, to a maximum of 400 mg/day, including the basal dose given by the oral or rectal route). Pain intensity and relief and symptom scores were recorded every day and at the end of each phase of the crossover. The mean age of the patients was 66.1 years (SD 13.5 years); 36 were female, and 44 completed both periods. Patients dropped out due to adverse effects (15 patients) and refusal (1 patient). No differences in the use of rescue dose of oral tramadol were observed between the groups. No differences in pain intensity and relief scores, or in other symptoms between the two treatments were observed. No differences in treatment efficacy as judged by the clinician (P=0.73), in patient compliance (P=0.35), or in patient satisfaction regarding treatment (P<0.35) were found. No differences in adverse effects were found between the two treatments (25.5%, 13 patients, and 20.4%, 11 patients, with oral and rectal treatment, respectively). The proportion of preferences favored oral administration for both physicians (P=0.0002) and patients (P=0.002). Rectal administration of tramadol appears a reliable, noninvasive alternative method of pain control for patients no longer responsive to non-opioid analgesics, unable to take oral tramadol.

Bioavailabilities of rectal and oral methadone in healthy subjects

AIMS

Rectal administration of methadone may be an alternative to intravenous and oral dosing in cancer pain, but the bioavailability of the rectal route is not known. The aim of this study was to compare the absolute rectal bioavailability of methadone with its oral bioavailability in healthy humans.

METHODS

Seven healthy subjects (six males, one female, aged 20-39 years) received 10 mg d(5)-methadone-HCl rectally (5 ml in 20% glycofurol) together with either d(0)-methadone intravenously (5 mg) or orally (10 mg) on two separate occasions. Blood samples for the LC-MS analyses of methadone and it's metabolite EDDP were drawn for up to 96 h. Noninvasive infrared pupillometry was performed at the same time as blood sampling.

RESULTS

The mean absolute rectal bioavailability of methadone was 0.76 (0.7, 0.81), compared to 0.86 (0.75, 0.97) for oral administration (mean (95% CI)). Rectal absorption of methadone was more rapid than after oral dosing with Tmax values of 1.4 (0.9, 1.8) vs. 2.8 (1.6, 4.0) h. The extent of formation of the metabolite EDDP did not differ between routes of administration. Single doses of methadone had a duration of action of at least 10 h and were well tolerated.

CONCLUSIONS

Rectal administration of methadone results in rapid absorption, a high bioavailability and long duration of action. No evidence of presystemic elimination was seen. Rectal methadone has characteristics that make it a potential alternative to intravenous and oral administration, particularly in cancer pain and palliative care.

Methadone for cancer pain

BACKGROUND

Methadone is an opioid used in the management of cancer pain both in opioid naïve patients and in rotation from other opioids. A particular role in neuropathic pain has been suggested. The quest for evidence based palliative care prompted a formal appraisal of methadone in comparison with other analgesics.

OBJECTIVES

To determine the effectiveness and safety of methadone analgesia in cancer pain patients.

SEARCH STRATEGY

MEDLINE (1966 to August 2002), EMBASE (1980 to August 2002), CancerLit (1993 to August 2002), CINAHL (1982 to August 2002) and Cochrane databases were searched using a strategy developed with the Cochrane Pain, Palliative and Supportive Care Group. Assiduous efforts were made to identify unpublished or current trial work.

SELECTION CRITERIA

Randomised controlled trials of methadone against active or placebo comparator in patients with cancer pain were included. Outcome measures sought were reduction in pain intensity measured by an appropriate scale, adverse effects, attrition, patient satisfaction and quality of life. There were no language restrictions. Absence of patient reported data was an exclusion criterion.

DATA COLLECTION AND ANALYSIS

Eligible studies were selected with independent collaboration from a colleague in Bristol (AND). Full text was retrieved if any uncertainty about eligibility remained. Non-English texts were screened by Cochrane contacts aware of the eligibility criteria. Quality assessment and data extraction were conducted using standardised data forms. Drug and placebo dose, titration, route and formulation were compared and detail of all outcome measures (if available) recorded.

MAIN RESULTS

Eight randomised controlled trials (five double blinded, two crossover) with 356 recruits and 326 completing patients were included. All involved active placebo (five morphine, one dextromoramide or pethidine, one diamorphine with cocaine mixture). All employed different starting doses, titration regimens and pain scoring scales. Few presented complete pain data sets and no meta-analysis has been possible. No differentiation by cancer pain syndrome was made. Complete adverse events data were recorded in every study, and were similar in incidence and severity to those experienced with morphine.

REVIEWERS' CONCLUSIONS

There is evidence to suggest that methadone is an analgesic with similar efficacy to morphine and a comparable side effect profile. However, the majority of studies involved single dose comparisons or short term use. This methodology fails to reproduce clinical practice. Therefore there is a very significant danger that the effects of methadone accumulation leading to delayed onset of adverse effects which occurs with chronic administration has not been represented. Fixed interval dosing schedules conducted over several days are associated with a high risk of serious morbidity and mortality. There is no trial evidence to support the proposal that methadone has a particular role in neuropathic pain of malignant origin. Conclusions have been limited by the variations in trial design, dosing regimens and limited presentation of primary outcome data. The complex and highly individual pharmacokinetics of methadone require that experienced clinicians take responsibility for initiating, titrating and monitoring this drug.

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.

The use of methadone for cancer pain

Methadone is not a new analgesic drug [69]. Several studies have demonstrated that methadone is a valid alternative to morphine, hydromorphone, and fentanyl for the treatment of cancer-related pain, and extensive reviews on the subject have been published in recent years [10,23,25,64,70,71]. Most people involved in pain therapy, however, are not well informed about the properties of methadone. The authors believe that the low cost of methadone paradoxically contributes to the limited knowledge of its characteristics and to the restricted therapeutic use of this drug. The low cost of methadone means there is little financial incentive for pharmaceutical companies to invest in research or to disseminate scientific information. Unfortunately, the lack of scientific information from pharmaceutical companies frequently results in a lack of knowledge on the part of physicians. Unless the existing approach changes, both culturally and politically, ignorance about methadone will persist among medical experts. The low cost of methadone, rather than being an advantage, will result in the limited exploitation of an effective drug.

Methadone use in cancer patients with pain: a review

In recent years a better understanding of the pharmacologic and pharmacokinetic properties of methadone, including equianalgesic ratios has led to its increased use as a second line opioid for the treatment of pain in patients with cancer. Methadone may be an important alternative for those who have side effects related to the use of other opioids because it has no known active metabolites, is well absorbed by oral and rectal routes, and also has the advantage of very low cost. However, it has a long, unpredictable half-life, which can result in accumulation and toxicity in some patients. In addition, rotation to methadone as a second line agent is more complex than with other opioids because of its increased potency in those patients who are opioid tolerant, particularly those who have been on higher doses of other opioids. Future research should address the use of methadone as a first-line agent in the management of cancer pain, its use in patients with neuropathic pain, and in those who develop rapid tolerance to other opioids. In some patients with cancer the long half-life of methadone offers the advantage of extended dosing intervals to 12 and even 24 hours, further research is also needed in this area.

Opioid switch to oral methadone in cancer pain

The occurrence of undesirable side effects due to opioids (delirium, confusion, myoclonus, nausea, emesis) is one of the major complications in the management of pain, especially in chronic cancer pain states. Methadone, as an alternative to morphine, has been proposed in the control of opioid-induced toxicity. Methadone is a synthetic opioid, with mu and delta receptor activity, associated with the capacity to inhibit N-methyl-D-aspartate receptors. Questions have arisen concerning its equianalgesic ratio since its rediscovery over the past few years and are certainly related to its receptor interactions. Aspects of its pharmacology, indications, and switching modalities are discussed here. Opioid rotation is a new tool in the management of cancer pain, deserving more attention.

Opioid rotation for cancer pain: rationale and clinical aspects

BACKGROUND

Some patients with cancer pain may develop uncontrolled adverse effects, including generalized myoclonus, delirium, nausea and emesis, or severe sedation before achieving adequate analgesia during opioid dose titration. Sequential therapeutic trials should be considered to determine the most favorable drug.

METHODS

Recent literature was taken into account when reviewing the rationale and potential of opioid rotation.

RESULTS

When aggressive attempts to prevent adverse effects fail, drug rotation should be considered, because sequential therapeutic trials can be useful in identifying the most favorable drug. Different mechanisms, including receptor activity, the asymmetry in cross-tolerance among different opioids, different opioid efficacies, and accumulation of toxic metabolites can explain the differences in analgesic or adverse effect responses among opioids in a clinical setting.

CONCLUSIONS

When pain is relieved inadequately by opioid analgesics given in a dose that causes intolerable side effects despite routine measures to control them, treatment with the same opioid by an alternative route or with an alternative opioid administered by the same route should be considered. Opioid rotation may be useful in opening the therapeutic window and for establishing a more advantageous analgesia/toxicity relationship. By substituting opioids and using lower doses than expected according to the equivalency conversion tables, it is possible in the majority of cases to reduce or relieve the symptoms of opioid toxicity in those patients who were highly tolerant to previous opioids while improving analgesia and, as a consequence, the opioid responsiveness.

Pain and Symptom Management in Palliative Care

BACKGROUND: Pain, dyspnea, and anorexia are common symptoms experienced by patients with cancer and often are poorly managed. METHODS: The incidence and causes of these symptoms are described, as well as factors that exacerbate or ameliorate their impact. RESULTS: Pharmacologic management of cancer pain is based on the use of a sequential "ladder" that incorporates nonopioid, opioid, and adjuvant drugs, depending on the severity of the pain. This approach usually is effective. Other symptoms of advanced disease may be more difficult to control. CONCLUSIONS: Adherence to an adequate pain-control strategy will significantly enhance palliation of pain in patients with cancer.