Prescription of analgesics to patients in opioid maintenance therapy: a pharmacoepidemiological study

AIMS

The primary aim of the present study is to determine the one year periodic prevalence of dispension of different analgesics to patients in long term opioid maintenance therapy (OMT). The secondary aim is to determine to which extent non-opioid analgesics are used as first line analgesics.

DESIGN

The study is a pharmacoepidemiological study with cross sectional data and cohort data. Data on patients in long term OMT in Norway were obtained from the complete national Norwegian Prescription Database (NorPD).

FINDINGS

The analgesics with the highest one year periodic prevalence were NSAIDs (22%), codeine-paracetamol combinations (9%), paracetamol (7%) and tramadol (2.5%). During both 2007 and 2008 a total of 12% of the study population received at least one dispension of another opioid in addition to the opioid used for OMT. In 55% of the cases where OMT patients had not received an analgesic the preceding year an NSAID was the first or only dispensed analgesic whereas paracetamol-codeine was the first or only dispensed analgesic in 29% of the cases.

CONCLUSIONS

This study has documented an equally high one year periodic prevalence of opioid dispensions in OMT patients as in the general population as well as a high one year periodic prevalence of dispensions of NSAIDs. Dispension of codeine-paracetamol has a relatively high one-year prevalence and is frequently used as a first line analgesic.

Starting step III opioids for moderate to severe pain in cancer patients: dose titration: a systematic review

The European Association for Palliative Care recommendation for starting morphine for cancer pain is dose titration with immediate release (IR) oral morphine given every 4 h with additionally doses for breakthrough pain. As part of a EU 6th framework programme to revise the guidelines we review the evidence regarding starting treatment and dose titration of opioids in adult patients with moderate to severe cancer pain. Relevant papers were identified though a systematic search in Medline for papers published until the end of 2009. We identified 15 relevant papers. Thirteen papers were descriptive papers reporting the results from starting treatment with oral morphine (six studies), starting treatment with intravenous morphine (two studies) and starting treatment with transdermal fentanyl (four studies). All treatment strategies resulted in acceptable pain control and were well tolerated. Two randomized controlled trials were identified. One study compared starting opioid treatment with intravenous morphine versus IR oral morphine and one study compared IR oral morphine versus sustained release oral morphine.

Associations between recreational exercise and chronic pain in the general population: evidence from the HUNT 3 study

The evidence for an association between leisure-time physical activity and prevalence of pain is insufficient. This study investigated associations between frequency, duration, and intensity of recreational exercise and chronic pain in a cross-sectional survey of the adult population of a Norwegian county (the Nord-Trøndelag Health Study; HUNT 3). Of the 94,194 invited to participate, complete data were obtained from 46,533 participants. Separate analyses were performed for the working-age population (20-64 years) and the older population (65 years or more). When defined as pain lasting longer than 6 months, and of at least moderate intensity during the past month, the overall prevalence of chronic pain was 29%. We found that increased frequency, duration, and intensity of exercise were associated with less chronic pain in analyses adjusted for age, education, and smoking. For those aged 20-64 years, the prevalence of chronic pain was 10-12% lower for those exercising 1-3 times a week for at least 30 minutes duration or of moderate intensity, relative to those not exercising. Dependent on the load of exercise, the prevalence of chronic pain was 21-38% lower among older women who exercised, relative to those not exercising. Similar, but somewhat weaker, associations were seen for older men. This study shows consistent and linear associations between frequency, duration, and intensity of recreational exercise and chronic pain for the older population, and associations without an apparent linear shape for the working-age population.

Driving functions in a video simulator in chronic non-malignant pain patients using and not using codeine

BACKGROUND AND AIMS

A considerable number of Europeans suffer from chronic pain and are using opioids, particularly of the weak type. It is a clinical impression that many of these are driving or wish to drive a car. The aims of this study were to investigate if codeine influences driving ability in a simulator, and to examine if chronic pain per se might impair such functions.

METHODS

Twenty patients with chronic pain on long-term codeine therapy were compared to 20 chronic pain patients not using codeine in a video driving simulator test. The chronic pain patients were then compared to 20 healthy controls. The primary outcome measures were reaction time and number of missed reactions.

RESULTS

The patients using codeine 120-270 mg (mean 180 mg) daily showed the same driving skills as patients not using codeine, and the codeine level did not affect the results. This was the case both 1h after intake of a single dose of 60 mg codeine and five or more hours after the last codeine intake. The reaction times were significantly slower for the chronic pain patients, in both rural and urban driving conditions, compared to the healthy controls (difference 0.11s. and 0.12s., respectively). The chronic pain patients missed almost twice as many reactions to traffic signs. There were no difference between the groups in steering precision.

CONCLUSION

The main finding in this simulator study was that codeine does not impair driving-related abilities over and above what is associated with chronic pain per se.

Prescriptions of opioids to children and adolescents; a study from a national prescription database in Norway

BACKGROUND

Analgesics are among the groups of drugs most frequently prescribed to children and adolescents. The prevalence of opioid use in children and adolescents is, however, not known.

AIM

The primary aim was to determine the 1-year periodic prevalence of opioid dispension in Norwegian children and adolescents below 18 years of age. The secondary aim was to determine to which extent children and adolescents receive opioids for acute or chronic pain.

METHODS

All pharmacies in Norway submit data electronically to the Norwegian Prescription Database on all dispensed prescriptions. All prescriptions to any individual are identified with a pseudonym. All Norwegians who were dispensed opioids from 2004 to 2007 are included in the study.

RESULTS

In 2004, 6386 children and adolescents received opioid dispensions, a number which had increased by 35% to 8607 in 2007. These numbers correspond to an increase in 1-year periodic prevalence from 0.59 to 0.79%. Each year during the study period, approximately 95% of the patients received only one or two opioid dispensions. Only 262 Norwegian children and adolescents below 18 years of age received opioid dispensions in three successive years from 2005 to 2007. About 93-95% of children and adolescents receiving opioids each year received the weak opioid codeine.

CONCLUSIONS

The 1-year periodic prevalence of opioid use in Norwegian children and adolescents is only one-sixteenth of the previously reported prevalence in the Norwegian adult population. Children and adolescents primarily receive opioids for acute pain.

Patients with problematic opioid use can be weaned from codeine without pain escalation

BACKGROUND

Brief treatments for chronic non-malignant pain patients with problematic opioid use are warranted. The aims of the present study were to investigate (1) whether it is possible to withdraw codeine use in such patients with a brief cognitive-behavioural therapy (CBT), (2) whether this could be done without pain escalation and reduction in quality of life and (3) to explore the effects of codeine reduction on neurocognitive functioning.

METHODS

Eleven patients using codeine daily corresponding to 40-100 mg morphine were included. Two specifically trained physicians treated the patients with six CBT sessions, tapering codeine gradually within 8 weeks. Codeine use, pain intensity, quality of life and neuropsychological functioning were assessed at pre-treatment to the 3-month follow-up.

RESULTS

Codeine use was significantly reduced from mean 237 mg [standard deviation (SD) 65] pre-treatment to 45 mg (SD 66) post-treatment and to 48 mg (SD 65) at follow-up without significant pain escalation or reductions in quality of life. Moreover, neuropsychological functioning improved significantly on some tests, while others remained unchanged.

CONCLUSION

The promising findings of codeine reduction in this weaning therapy programme for pain patients with problematic opioid use should be further evaluated in a larger randomized control trial comparing this brief CBT with both another brief treatment and attention placebo condition.

Increasing use of opioids from 2004 to 2007 - pharmacoepidemiological data from a complete national prescription database in Norway

BACKGROUND

A high opioid consumption for cancer related and acute pain may indicate adequate pain treatment. Analysis of a national, compulsory and complete database of all dispensed prescription drugs in Norway (NorPD) may reveal important epidemiological data on prescription pattern of opioids. This study investigated the prevalence of opioid dispensions in 2004-2007 and explored patterns of use.

METHODS

All pharmacies in Norway submit data electronically to NorPD on all dispensed prescriptions. All prescriptions to any individual are identified by a unique pseudonym. All persons who were dispensed opioids from 2004 to 2007 are included in the study. Cancer patients are identified by a reimbursement code. Non-cancer pain indications are inferred from pattern of prescriptions.

RESULTS

470,638 Norwegians were dispensed opioids in 2007, corresponding to 9.7% of the population (13.0% of adults). Only 13,220 persons (2.8% of all patients) received opioids for cancer pain, accounting for 10% of all dispensed opioids measured in defined daily doses (DDDs). Among persons with non-cancer pain 77% received only one dispension per year or less than 50 DDDs/year. Fifteen percent received from 50 to 200 DDDs/year. Only 13,846 (4%) received >400 DDDs/year and are likely to be daily users for chronic non-cancer pain. From 2004 to 2007 a 9 % increase was observed in the number of persons receiving opioids and the number of dispensions, whereas opioid types, doses, and indications appeared stable.

INTERPRETATION

From these prescription patterns it can be concluded that the majority of patients received opioids for acute, non-cancer pain.

Prescription pattern of codeine for non-malignant pain: a pharmacoepidemiological study from the Norwegian Prescription Database

BACKGROUND

Opioid prescription for pain relief is increasing. Codeine is the dominating opioid in several European countries, with Norway being among the highest codeine users.

AIM

To determine whether codeine is primarily used for acute pain or whether there is a prescription pattern indicating problematic opioid use.

METHODS

All pharmacies in Norway are obliged to submit data electronically to the Norwegian Prescription Database at the Norwegian Institute of Public Health on all dispensed prescriptions. Because all prescriptions are identified with a unique person identifier, it is possible to identify all prescriptions to one subject. All subjects who had prescription(s) of codeine dispensed to them in 2004, 2005 or 2006 are included in the study.

RESULTS

385 190 Norwegian persons had at least one prescription of codeine dispensed to them due to non-cancer pain in 2005, corresponding to a 1-year periodic prevalence of 8.3%. 223 778 (58%) received only one prescription in 2005, 121 025 (31%) received more than one prescription but <120 defined daily doses (DDDs), 30 939 (8%) received between 120 and 365 DDDs, 7661 (2%) between 365 and 730 DDDs, while only 1787 (0.5%) exceeded the maximum recommended dose of 730 DDDs. In the latter group, co-medication with benzodiazepines (65%) and carisoprodol (45%) was prevalent.

CONCLUSION

About one in 10 adult persons in Norway were dispensed codeine in 2005. A majority (58%) received codeine only once, most likely for acute pain, whereas a small minority (0.5%) had a prescription pattern indicating problematic opioid use.

A controlled comparison between single doses of intravenous and intramuscular morphine with respect to analgesic effects and patient safety

BACKGROUND AND AIM OF INVESTIGATION: Intramuscular (IM) administration has been considered to be safer than intravenous (IV) for opioids on wards, but a comparative knowledge of patient safety and analgesic potency following a single dose of IV and IM administration is lacking. This study was carried out to compare patient safety and analgesic efficacy of a single and high dose of morphine given IM or IV for post-operative pain management.

MATERIALS AND METHODS

Thirty-eight patients with post-operative pain following hip replacement surgery were given IM or IV morphine 10 mg at a specified pain level. The study was randomized and double blinded. Time to onset of analgesic effect (11-point numeric rating scale), respiratory function (p(a)CO2, p(a)O2, and respiratory rate), level of sedation (5-point verbal rating scale), and hemodynamic function were recorded.

RESULTS

In the IV group there was a slight but significant increase in p(a)CO2 after 5, 10, and 15 min compared with the IM group (5.2 vs. 4.8, 5.4, vs. 5.0 and 5.5 vs. 5.1 kPa, respectively). The IV group had a significantly faster onset of analgesic effect than the IM group (5 vs. 20 min). Between 5 and 25 min after morphine administration, pain status in the IV group was significantly improved compared with the IM group. Patients in the IV group were slightly more sedated than the IM group 5 and 10 min after morphine.

CONCLUSION

A 10 mg bolus dose of IV morphine given to patients with moderate pain after surgery does not cause severe respiratory depression, but provides more rapid and better initial analgesia than 10 mg given IM. IV morphine even at a dose as high as 10 mg IV is well tolerated if there is a certain level of pain at its administration. The safety of IV morphine on the general ward needs to be further explored in adequately controlled studies.

Clinical pharmacology of methadone for pain

BACKGROUND

This topical review addresses methadone's pharmacology, its application in malignant and non-malignant pain conditions, practical issues related to methadone for the treatment of pain and its influence on QTc time.

METHODS

Relevant papers were identified in PubMed and EMBASE.

RESULTS

Methadone is advocated by experts as a second line opioid when first line opioids fail to provide a satisfactory balance between pain control and side effects (opioid switching). Although randomized-controlled studies are lacking, current evidence suggests that switching to methadone in this situation reduces pain intensity. However, interindividual variability in its pharmacokinetics make its application challenging and metabolism by CYP 3A4 and 2B6 implies a substantial risk of drug-drug interactions. Several ways of switching to methadone have been presented, with a gradual switch during 3 days or 'stop and go' as the dominating strategies. Episodes of torsade de pointes arrhythmia during methadone treatment have been reported in patients with other risk factors for arrhythmia, while small prospective studies have reported a small, lasting and stable increase in QTc time. The extensive use of methadone for opioid replacement in addicts has added additional patient barriers to its use for pain control.

CONCLUSION

In spite of challenges related to the variable pharmacokinetics and concerns regarding increase in QTc time, current evidence indicates that opioid switching to methadone improves pain control in a substantial proportion of patients who are candidates for opioid switching. Measures must be instituted to secure that patients receiving methadone for pain are not considered opioid addicts.

Assessment of pain

Valid and reliable assessment of pain is essential for both clinical trials and effective pain management. The nature of pain makes objective measurement impossible. Acute pain can be reliably assessed, both at rest (important for comfort) and during movement (important for function and risk of postoperative complications), with one-dimensional tools such as numeric rating scales or visual analogue scales. Both these are more powerful in detecting changes in pain intensity than a verbal categorical rating scale. In acute pain trials, assessment of baseline pain must ensure sufficient pain intensity for the trial to detect meaningful treatment effects. Chronic pain assessment and its impact on physical, emotional, and social functions require multidimensional qualitative tools and health-related quality of life instruments. Several disease- and patient-specific functional scales are useful, such as the Western Ontario and MacMaster Universities for osteoarthritis, and several neuropathic pain screening tools. The Initiative on

METHODS

Measurement, and Pain Assessment in Clinical Trials recommendations for outcome measurements of chronic pain trials are also useful for routine assessment. Cancer pain assessment is complicated by a number of other bodily and mental symptoms such as fatigue and depression, all affecting quality of life. It is noteworthy that quality of life reported by chronic pain patients can be as much affected as that of terminal cancer patients. Any assessment of pain must take into account other factors, such as cognitive impairment or dementia, and assessment tools validated in the specific patient groups being studied.

Chronic non-malignant pain patients report as poor health-related quality of life as palliative cancer patients

BACKGROUND

Patients with chronic non-malignant pain (CNMP) conditions are known to report reduced health-related quality of life (HRQoL). The objective of this exploratory study was to compare HRQoL between patients admitted to a multidisciplinary pain centre, palliative cancer (PC) patients and national norms.

METHODS

HRQoL data from 288 patients with CNMP admitted to the multidisciplinary pain centre at Trondheim University Hospital were compared with 434 patients with advanced cancer included in a trial of comprehensive palliative care in the hospital palliative medicine unit and national norms. HRQoL was assessed using the EORTC QLQ-C30. Age- and gender-adjusted norm data were calculated and compared between the two groups.

RESULTS

Scores from both groups deviated from adjusted norm data on all scales, with poorer functioning and more symptoms. Compared with PC patients, CNMP patients reported a larger deviation (worse scores) on global quality of life, cognitive functioning, pain, sleep disturbances and financial difficulties. Deviations from norm data were similar for physical, social and emotional functioning, diarrhoea, dyspnoea and fatigue. PC patients reported worse scores on role functioning, nausea/vomiting, loss of appetite and constipation.

CONCLUSION

CNMP patients admitted to multidisciplinary pain centres report significantly reduced HRQoL, in addition to severe pain. They consider their HRQoL to be as poor as HRQoL reported from dying cancer patients and substantially poorer than national norms. Factors other than the biological severity of the disease seem to be of major importance for self-reported HRQoL.

Validation and comparison of the health-related quality-of-life instruments EORTC QLQ-C30 and SF-36 in assessment of patients with chronic nonmalignant pain

The EORTC QLQ-C30 health-related quality of life (HRQoL) questionnaire was developed for use in clinical cancer trials. It has also been applied in studies of patients with chronic nonmalignant pain in spite of nondocumented validity. Validation of the EORTC QLQ-C30 in this patient population and comparison with the traditional first choice HRQoL instrument in chronic nonmalignant pain, the SF-36, are, therefore, required. Two hundred eighty-six patients admitted to the tertiary multidisciplinary pain center at St. Olavs University Hospital in Trondheim, Norway, completed both the EORTC QLQ-C30 and the SF-36 at admittance. Correlations between EORTC QLQ-C30 and SF-36 measures of the same concept were between 0.70 and 0.81 for all five domains covered by both instruments. Internal consistency was below 0.70 for the EORTC QLQ-C30 scales physical functioning (0.57), pain (0.68), role functioning (0.43), cognitive functioning (0.66), and nausea/vomiting (0.53), as well as the SF-36 scale role emotional functioning (0.66). Large floor or ceiling effects were seen for several EORTC QLQ-C30 scales. While SF-36 addresses no other symptoms than pain and fatigue, the EORTC QLQ-C30 also includes sleep, financial difficulties, nausea/vomiting, dyspnea, appetite loss, constipation, and diarrhea. Even though some EORTC QLQ-C30 scales have unsatisfactory internal consistency, EORTC QLQ-C30, similar to SF-36, has overall acceptable psychometric properties. The EORTC QLQ-C30 is a valid alternative to the SF-36 when a broader assessment of symptoms is desired.

Serum and cerebrospinal fluid morphine pharmacokinetics after single doses of intravenous and intramuscular morphine after hip replacement surgery

AIM

To compare the time course of morphine and metabolite concentrations in serum and cerebrospinal fluid (CSF) after intravenous and intramuscular administration after surgery.

METHODS

This was a randomized double-blind, double-dummy study in patients who had undergone hip replacement surgery. Morphine (M, 10 mg) was administered intravenously (IV) or intramuscularly (IM). Arterial blood and CSF samples (from a spinal catheter) were drawn simultaneously at 10, 30, 60, and 120 min after administration. Morphine and metabolites [morphine-3-glucuronide (M-3-G), morphine-6-glucuronide (M-6-G), and normorphine (NM)] were determined by a validated liquid chromatography-tandem mass spectrometry method.

RESULTS

Thirty-eight patients were included: 13 men and 25 women, 20 in the IV, 18 in the IM group. Serum concentrations of M after 10 min were consistently higher after IM than IV, concentrations of M-3-G and M-6-G after IM surpassed those of IV after 45 min. NM was not found. None of the metabolites was found in CSF. CSF morphine concentrations and CSF/serum concentration ratios were consistently higher after IV compared to IM. The mean AUC(CSF)/AUC(serum) (0-120 min) concentration ratios were 0.18 and 0.09 after IV and IM, respectively.

CONCLUSIONS

The uptake of morphine to the CSF was consistently higher after IV administration than after IM already after 10 min. The higher CSF concentration may be caused by an initially higher morphine blood/CSF gradient following IV morphine injection. The pharmacokinetic findings are compatible with a more rapid and extensive initial effect of IV morphine compared with IM.

Long term methadone for chronic pain: a pilot study of pharmacokinetic aspects

Methadone is used as an alternative opioid when first line opioids fail to provide adequate pain control. Highly variable morphine:methadone dose ratios make switching challenging and little is known about the pharmacokinetics of long lasting methadone treatment for pain. Twelve patients treated with morphine for chronic non-malignant pain were switched to methadone. Seven of these patients continued with methadone throughout the nine months study period and only minor dose adjustments were performed. Serum concentrations of morphine, methadone and their metabolites were measured at baseline, day one and two, after dose titration and one week, five weeks, three months and nine months after the end of dose titration. Serum concentrations of methadone and its metabolite EDDP did not change significantly from the end of dose titration and during the nine months (repeated measures ANOVA: p=0.88 and p=0.06). Very low correlation between dose ratios and serum concentration ratios between morphine and methadone was observed. Large interindividual differences in serum concentrations and metabolism were observed. Our findings contradict that autoinduction of methadone metabolism takes place during long term treatment and supports that a 3-day opioid switch from morphine to methadone followed by a one week titration seems pharmacologically sound.

Opioid switching from morphine to methadone causes a minor but not clinically significant increase in QTc time: A prospective 9-month follow-up study

Case reports and retrospective studies suggest that methadone causes an increase in QTc (QT time corrected for heart rate) time and risk of torsades de pointes arrhythmia. No prospective studies in pain patients have been conducted, and data on whether a methadone-induced increase in QTc time persists during long-term treatment have not been reported. Eight chronic nonmalignant pain patients experiencing insufficient pain control or intolerable side effects during treatment with oral morphine switched to oral methadone and were included in this study. Electrocardiograms were obtained at baseline and at follow-up 2 weeks, and 3 and 9 months after the opioid switch. Start of methadone caused a minor but statistically significant increase in QTc time, while fluctuations in QTc during treatment with stable doses of methadone were neither clinically nor statistically significant. We observed no episodes of arrhythmias.

[Genetic variation-- important for the clinical effect of opioids?]

The individual variability of opioid pharmacology suggests that the patients' genetic disposition influences the response to opioids. Given the complexity of morphine pharmacology, variability may be caused by several genes. Data suggest that variability in genes encoding the enzyme metabolising morphine (UGT2B7 gene), mu-opioid receptors (OPRM1 gene) and BBB transport of morphine by multidrug resistance transporters (MDR1 gene) influence the clinical efficacy of morphine. Furthermore, variability in an enzyme-degrading catecholamines (COMT gene) may also alter the efficacy of morphine, which shows that genetic variability in non-opioid systems may indirectly influence the clinical opioid efficacy. Results obtained so far strongly suggest that opioid efficacy is partly related to inborn properties caused by genetic variability.

Genetic variability and clinical efficacy of morphine

The individual variability of opioid pharmacology suggests that the patients' genetic disposition influences the response to opioids. Given the complexity of morphine pharmacology, variability may be caused by several genes. We review data which shows that variability in genes coding the enzyme metabolizing morphine (UGT2B7 gene), mu-opioid receptors (OPRM gene) and blood-brain barrier (BBB) transport of morphine by multidrug resistance transporters (MDR1 gene) influences the clinical efficacy of morphine. Furthermore, variability in an enzyme degrading catecholamines (COMT gene) alters the efficacy of morphine demonstrating that genetic variability in non-opioid systems may indirectly influence the clinical efficacy from morphine. Thus, results obtained so far strongly argue that opioid efficacy is partly related to inborn properties caused by genetic variability.

The 118 A > G polymorphism in the human mu-opioid receptor gene may increase morphine requirements in patients with pain caused by malignant disease

BACKGROUND

Dispositions for genes encoding opioid receptors may explain some variability in morphine efficacy. Experimental studies show that morphine and morphine-6-glucuronide are less effective in individuals carrying variant alleles caused by the 118 A > G polymorphism in the mu-opioid receptor gene (OPRM1). The purpose of the study was to investigate whether this and other genetic polymorphisms in OPRM1 influence the efficacy of morphine in cancer pain patients.

METHODS

We screened 207 cancer pain patients on oral morphine treatment for four frequent OPRM1 gene polymorphisms. The polymorphisms were the -172 G > T polymorphism in the 5'untranslated region of exon 1, the 118 A > G polymorphism in exon 1, and the IVS2 + 31 G > A and IVS2 + 691 G > C polymorphisms, both in intron 2. Ninety-nine patients with adequately controlled pain were included in an analysis comparing morphine doses and serum concentrations of morphine and morphine metabolites in the different genotypes for the OPRM1 polymorphisms.

RESULTS

No differences related to the -172 G > T, the IVS2 + 31 G > A and the IVS2 + 691 G > C polymorphisms were observed. Patients homozygous for the variant G allele of the 118 A > G polymorphism (n = 4) needed more morphine to achieve pain control, compared to heterozygous (n = 17) and homozygous wild-type (n = 78) individuals. This difference was not explained by other factors such as duration of morphine treatment, performance status, time since diagnosis, time until death, or adverse symptoms.

CONCLUSION

Patients homozygous for the 118 G allele of the mu-opioid receptor need higher morphine doses to achieve pain control. Thus, genetic variation at the gene encoding the mu-opioid receptor contributes to variability in patients' responses to morphine.