Comparison of the analgesic and intestinal effects of fentanyl and morphine in rats

β-caryophyllene inhibits heroin self-administration, but does not alter opioid-induced antinociception in rodents

A growing body of research indicates that β-caryophyllene (BCP), a constituent present in a large number of plants, possesses significant therapeutic properties against CNS disorders, including alcohol and psychostimulant use disorders. However, it is unknown whether BCP has similar therapeutic potential for opioid use disorders. In this study, we found that systemic administration of BCP dose-dependently reduced heroin self-administration in rats under an FR2 schedule of reinforcement and partially blocked heroin-enhanced brain stimulation reward in DAT-cre mice, maintained by optical stimulation of midbrain dopamine neurons at high frequencies. Acute administration of BCP failed to block heroin conditioned place preference (CPP) in male mice, but attenuated heroin-induced CPP in females. Furthermore, repeated dosing with BCP for 5 days facilitated the extinction of CPP in female but not male mice. In the hot plate assay, pretreatment with the same doses of BCP failed to enhance or prolong opioid antinociception. Lastly, in a substitution test, BCP replacement for heroin failed to maintain intravenous BCP self-administration, suggesting that BCP itself has no reinforcing properties. These findings suggest that BCP may have certain therapeutic effects against opioid use disorders with fewer unwanted side-effects by itself.

Medicinal grade opium tincture for severe diarrhea: effect revisited in observational study

PURPOSE OF REVIEW

Chronic diarrhea is a common disorder that interferes with normal daily activities and results in poor quality of life. Fecal urgency and incontinence often necessitate clinical consultation, but the pathophysiological mechanisms are difficult to differentiate in a clinical setting. Therefore, drugs targeting the opioid receptors, such as diphenoxylate and loperamide, are typically used, as they reduce both gut motility and secretion.

RECENT FINDINGS

For severe diarrhea, morphine-containing extemporaneous opium tincture drops have recently been reprofiled to a pharmaceutical. The drug is indicated for severe diarrhea in adults when other antidiarrheals do not give sufficient fecal emptying control. The pronounced effect is due to the liquid formulation with rapid onset as a drug dissolution step is avoided. A recent prospective, noninterventional study (CLARIFY) of patients treated with opioid drops demonstrates a rapid and sustained therapeutic effect. Tolerance does not develop for the antidiarrheal effect and no dependence was observed after discontinuation.

SUMMARY

This mini-review discusses the use of opium derivates for treatment of diarrhea, with an emphasis on opium drops as a new medicinal grade opium for the use as additional treatment of severe diarrhea, emphasizing its mechanism of action and evaluation of the risk-benefit ratio in the clinical setting.

Preclinical comparison of antinociceptive effects between ibuprofen, diclofenac, naproxen, and acetaminophen on acid-stimulated body stretching and acid-depressed feeding behaviors in rats

Pain is a major problem that burdens the health and economy of societies worldwide. Nonsteroidal anti-inflammatory drugs (NSAIDs) are over-the-counter medications that are widely indicated for mild to moderate pain conditions. Clinically, the selection of a medication among this class is mainly based according to both patient's and doctor's previous experiences. Herein, we studied differences in therapeutic efficacies among the most commonly prescribed NSAIDs and acetaminophen in inflammatory pain rat model. Body stretching and food consumption behaviors were assessed after intraperitoneal administration of lactic acid. Initially, different concentrations of lactic acid were evaluated in adult male rats in both behavioral models. Acid concentrations of 1.8 and 3.2% were selected to assess the effects of ibuprofen, diclofenac, naproxen, and acetaminophen in body stretching and feeding behaviors, respectively. In the feeding study, food restriction for 1-24 h prior to feeding studies was assessed at first, and 24 h was selected for further tests. Acetaminophen (100 mg/kg), diclofenac (10 mg/kg), ibuprofen (10-32 mg/kg), and naproxen (3.2-10 mg/kg) significantly decreased acid-stimulated body stretching. Likewise, acetaminophen (100 mg/kg), diclofenac (10 mg/kg), and ibuprofen (32 mg/kg) increased food consumption significantly after 3.2% lactic acid. There were no significant differences between different test drugs efficacies in both stretching and feeding behaviors. In conclusion, feeding behavior provides a good appraisal for pain and analgesic drugs in preclinical studies. There were comparable efficacies between all tested medications in both lactic acid-stimulated body stretching and -depressed feeding behaviors.

Respiratory effects of low and high doses of fentanyl in control and β-arrestin 2-deficient mice

We have investigated the potential acute desensitizing role of the β arrestin 2 (β-arr2) pathway on the ventilatory depression produced by levels of fentanyl ranging from analgesic to life-threatening (0.1 to 60 mg/kg ip) in control and β-arr2-deficient nonsedated mice. Fentanyl at doses of 0.1, 0.5, and 1 mg/kg ip-corresponding to the doses previously used to study the role of β-arr2 pathway-decreased ventilation, but along the V̇e/V̇co₂ relationship established in baseline conditions. This reduction in ventilation was therefore indistinguishable from the decrease in breathing during the periods of spontaneous immobility. Above 1.5 mg/kg, however, ventilation was depressed out of proportion of the changes in metabolic rate, suggesting a specific depression of the drive to breathe. The ventilatory responses were similar between the two groups. At high doses of fentanyl (60 mg/kg ip) 1 out of 20 control mice died by apnea versus 8 out of 20 β-arr2-deficient mice (P = 0.008). In the surviving mice, ventilation was however identical in both groups. The ventilatory effects of fentanyl in β-arr2-deficient mice, reported in the literature, are primarily mediated by the "indirect" effects of sedation/hypometabolism on breathing control. There was an excess mortality at very high doses of fentanyl in the β-arr2-deficient mice, mechanisms of which are still open to question, as the capacity of maintaining a rhythmic, although profoundly depressed, breathing activity remains similar in all of the surviving control and β-arr2-deficient mice.NEW & NOTEWORTHY When life-threatening doses of fentanyl are used in mice, the β-arrestin 2 pathway appears to play a critical role in the recovery from opioid overdose. This observation calls into question the use of G protein-biased μ-opioid receptor agonists, as a strategy for safer opioid analgesic drugs.

Pharmacokinetics and pharmacodynamics of cyclopropylfentanyl in male rats

BACKGROUND

Illicitly manufactured fentanyl and its analogs are a major driving force behind the ongoing opioid crisis. Cyclopropylfentanyl is a fentanyl analog associated with many overdose deaths, but limited knowledge is available about its pharmacology. In the present study, we developed a bioanalytical method for the determination of cyclopropylfentanyl and its main metabolite cyclopropylnorfentanyl and evaluated pharmacokinetic-pharmacodynamic relationships in rats.

METHOD

An ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for determination of cyclopropylfentanyl and cyclopropylnorfentanyl in rat plasma. Male Sprague-Dawley rats fitted with jugular catheters and temperature transponders received cyclopropylfentanyl (30, 100, and 300 μg/kg) or saline subcutaneously. Blood specimens were withdrawn over an 8-h time period, along with measurements of pharmacodynamic endpoints.

RESULTS

The analytical method was validated, and both analytes exhibited a low limit of quantification (15 pg/mL). Cyclopropylfentanyl caused dose-related increases in hot plate latency (ED₅₀ = 48 µg/kg) and catalepsy (ED₅₀ = 87 µg/kg) and produced long-lasting hypothermia at the highest dose. Plasma cyclopropylfentanyl rose rapidly in a dose-related fashion, reaching maximal concentration (C_max) after 15-28 min, whereas metabolite Cmax occurred later at 45-90 min. Cyclopropylfentanyl C_max values were similar to concentrations measured in non-fatal intoxications in humans; however, differences in parent drug: metabolite ratio indicated possible interspecies variance in metabolism.

CONCLUSION

Our study shows that cyclopropylfentanyl produces typical opioid-like effects in male rats. Cyclopropylfentanyl displays much greater analgesic potency when compared to morphine, suggesting that cyclopropylfentanyl poses increased overdose risk for unsuspecting users.

Oxycodone, fentanyl, and morphine amplify established neuropathic pain in male rats

Opioids are widely prescribed for chronic pain, including neuropathic pain, despite growing evidence of long-term harm. Previous preclinical studies have documented exacerbation of nociceptive hypersensitivity, including that induced by peripheral nerve injury, by morphine. The present series of behavioral studies sought to replicate and extend our prior research, which demonstrated a multimonth exacerbation of nociceptive hypersensitivity by a 5-day course of morphine initiated 10 days after nerve injury. The current studies demonstrate that enduring exacerbation of nociceptive hypersensitivity is not restricted to morphine, but rather is also created by the clinically relevant opioids fentanyl and oxycodone when these are likewise administered for 5 days beginning 10 days after nerve injury. Furthermore, enduring exacerbation of nociceptive hypersensitivity is also observed when the same dosing regimen for either morphine, fentanyl, or oxycodone begins 1 month after nerve injury. Finally, a striking result from these studies is that no such exacerbation of nociceptive hypersensitivity occurs when either morphine, fentanyl, or oxycodone dosing begins at the time of nerve injury. These results extend our previous findings that morphine exacerbates nociceptive hypersensitivity to the clinically relevant opioids fentanyl and oxycodone when administered after the development of nociceptive hypersensitivity, while also providing possible clinically relevant insight into when these opioids can be safely administered and not exacerbate neuropathic pain.

Alterations in Rat Accumbens Endocannabinoid and GABA Content during Fentanyl Treatment: The Role of Ghrelin

The opioid-induced rise of extracellular dopamine, endocannabinoid anandamide and γ-aminobutyric acid (GABA) concentrations triggered by opioids in the nucleus accumbens shell (NACSh) most likely participate in opioid reward. We have previously demonstrated that systemic administration of ghrelin antagonist (JMV2959) significantly decreased morphine-induced dopamine and anandamide (N-arachidonoylethanolamine, AEA) increase in the NACSh. Fentanyl is considered as a µ-receptor-selective agonist. The aim of this study was to test whether JMV2959, a growth hormone secretagogue receptor (GHS-R1A) antagonist, can influence the fentanyl-induced effects on anandamide, 2-arachidonoylglycerol (2-AG) and GABA in the NACSh and specify the involvement of GHS-R1A located in the ventral tegmental area (VTA) and nucleus accumbens (NAC). Using in vivo microdialysis in rats, we have found that pre-treatment with JMV2959 reversed dose dependently fentanyl-induced anandamide increases in the NACSh, resulting in a significant AEA decrease and intensified fentanyl-induced decreases in accumbens 2-AG levels, with both JMV2959 effects more expressed when administered into the NACSh in comparison to the VTA. JMV2959 pre-treatment significantly decreased the fentanyl-evoked accumbens GABA efflux and reduced concurrently monitored fentanyl-induced behavioural stimulation. Our current data encourage further investigation to assess if substances affecting GABA or endocannabinoid concentrations and action, such as GHS-R1A antagonists, can be used to prevent opioid-seeking behaviour.

Morphine-Induced Constipation Develops With Increased Aquaporin-3 Expression in the Colon via Increased Serotonin Secretion

Aquaporin-3 (AQP3) is a water channel that is predominantly expressed in the colon, where it plays a critical role in the regulation of fecal water content. This study investigated the role of AQP3 in the colon in morphine-induced constipation. AQP3 expression levels in the colon were analyzed after oral morphine administration to rats. The degree of constipation was analyzed after the combined administration of HgCl(2) (AQP3 inhibitor) or fluoxetine (5-HT reuptake transporter [SERT] inhibitor) and morphine. The mechanism by which morphine increased AQP3 expression was examined in HT-29 cells. AQP3 expression levels in rat colon were increased during morphine-induced constipation. The combination of HgCl(2) and morphine improved morphine-induced constipation. Treatment with morphine in HT-29 cells did not change AQP3 expression. However, 5-HT treatment significantly increased the AQP3 expression level and the nuclear translocation of peroxisome proliferator-activated receptor gamma (PPARγ) 1 h after treatment. Pretreatment with fluoxetine significantly suppressed these increases. Fluoxetine pretreatment suppressed the development of morphine-induced constipation and the associated increase in AQP3 expression in the colon. The results suggest that morphine increases the AQP3 expression level in the colon, which promotes water absorption from the luminal side to the vascular side and causes constipation. This study also showed that morphine-induced 5-HT secreted from the colon was taken into cells by SERT and activated PPARγ, which subsequently increased AQP3 expression levels.

Impact of concomitant antacid administration on gabapentin plasma exposure and oral bioavailability in healthy adult subjects

The aim of this open-label, randomized, and 3-period crossover study was to evaluate the influences of concomitant antacid administration on the plasma disposition, intestinal absorption, and urinary excretion of gabapentin in humans. Gabapentin (200 mg) was orally administered alone, with 1 g magnesium oxide (MgO), or with 20 mg omeprazole to 13 healthy adult subjects. Oral bioavailability (BA) of gabapentin was estimated by 24-h urine collection. The C(max), T(max) and AUC(0-∞) of gabapentin + MgO were significantly lower than that of gabapentin alone (by 33%, 36% and 43%, respectively) and gabapentin + omeprazole (by 29%, 46% and 40%, respectively). In contrast, no significant differences were observed in the plasma disposition parameters of gabapentin between the treatments with and without omeprazole. The gabapentin BA in the MgO treatment was significantly lower, by 32% and 39%, compared to the gabapentin alone and with omeprazole treatment, respectively. There was no significant difference in the gabapentin BA between the gabapentin alone and with omeprazole treatment. Concomitant MgO and omeprazole did not affect the renal clearance of gabapentin. In conclusion, concomitant MgO decreased the gabapentin exposure through the reduction of intestinal absorption extent and rate. This reduction may be independent of the suppression of gastrointestinal acidification caused by antacids.

Fentanyl sublingual: in breakthrough pain in opioid-tolerant adults with cancer

Fentanyl is a potent opioid with a short duration of action. Fentanyl sublingual has been formulated as a rapidly disintegrating tablet that is quickly absorbed, producing a fast onset of analgesia. In two randomized, double-blind clinical trials, fentanyl sublingual as single fixed or titrated doses reduced pain intensity during breakthrough pain episodes to a significantly greater extent than placebo in opioid-tolerant cancer patients. In a fixed-dose phase II trial and a titrated-dose phase III trial, fentanyl sublingual (as a single 400 μg dose and as titrated doses) reduced mean pain intensity difference (PID) to a significantly greater extent than placebo over the entire treatment period (up to 60 minutes), reaching statistical significance 15 minutes post-dose. In the titrated-dose study, the mean sum of PID (area under the PID vs time curve) at 30 minutes post-dose was significantly greater with fentanyl sublingual than placebo, with significant improvements in PID seen at 10 minutes maintained at 60 minutes post-dose. In the phase III study, patients receiving fentanyl sublingual were more satisfied with their treatment than patients receiving placebo (measured using the Patient Global Evaluation of Medication score), and almost half of all fentanyl sublingual recipients were satisfied or very satisfied with their treatment. Fentanyl sublingual was generally well tolerated in the two trials and most adverse events were mild to moderate in intensity.

Social isolation increases morphine intake: behavioral and psychopharmacological aspects

Environmental and situational factors are important determinants of recreational drug use in humans. We aimed to develop a reliable animal model for studying the effects of environmental variables on drug-seeking behavior using the 'social isolation/social restriction' paradigm. Adult Wistar rats housed in short-term isolation (21 days) consumed significantly more morphine solution (0.5 mg/ml) than rats living in pairs, both in one-bottle and in two-bottle tests. No differences were found in their water consumption. This effect was observed in both males and females and the results were also replicated after reversal of housing conditions. We also found that as little as 60-min of daily social-physical interaction with another rat was sufficient to completely abolish the increase in morphine consumption in socially restricted animals. We discuss some possible interpretations for these effects. These results indicate that environmental and situational factors influence drug intake in laboratory rats as they do in humans, and thus may be of interest in studying drug-seeking behavior in humans.

Intravenous Morphine Can Avoid Distressing Constipation Associated With Oral Morphine: A Retrospective Analysis of Our Experience in 11 Patients in the Palliative Care In-Patient Unit

Morphine is the preferred strong opioid analgesic. Most of the adverse effects, such as daytime drowsiness, dizziness, mental clouding, and effects on cognitive and psychomotor function or nausea and vomiting, usually resolve with time. The main continuing adverse effect of morphine is constipation, and prophylactic use of laxative is almost always required. We are presenting retrospective data of 11 patients admitted in our palliative care unit over the past 5 months for new (not yet received any opioid analgesic in any form) and severe cancer pain management. It was found that none of the patients was having constipation with intravenous morphine. This finding can be explained on the basis of differences in pharmacologic profiles, in affinity to opioid receptor, and a higher exposure of opioid-binding receptor in the GI tract after oral administration of morphine compared with intravenous morphine. This explanation was further affirmed as constipation and need for laxative was reported by 7 of the 11 patients when they were given the equi-analgesic oral doses of morphine. Thus, the route of administration seems to be responsible for the above finding; hence, further evaluation with prospective observation and data collection is being planned to look for external validity in a larger population catered by our palliative care unit.

MGM-9 [(E)-methyl 2-(3-ethyl-7a,12a-(epoxyethanoxy)-9-fluoro-1,2,3,4,6,7,12,12b-octahydro-8-methoxyindolo[2,3-a]quinolizin-2-yl)-3-methoxyacrylate], a derivative of the indole alkaloid mitragynine: a novel dual-acting mu- and kappa-opioid agonist with potent antinociceptive and weak rewarding effects in mice

Mitragynine is a major indole alkaloid isolated from the Thai medicinal plant Mitragyna speciosa that has opium-like properties, although its chemical structure is quite different from that of morphine. We attempted to develop novel analgesics derived from mitragynine, and thus synthesized the ethylene glycol-bridged and C10-fluorinated derivative of mitragynine, MGM-9 [(E)-methyl 2-(3-ethyl-7a,12a-(epoxyethanoxy)-9-fluoro-1,2,3,4,6,7,12,12b-octahydro-8-methoxyindolo[2,3-a]quinolizin-2-yl)-3-methoxyacrylate]. We hypothesized that a dual-acting mu- and kappa-opioid agonist could produce potent antinociceptive effects with fewer rewarding effects compared with mu agonists. In this study, MGM-9 exhibited high affinity for mu- and kappa-opioid receptors with Ki values of 7.3 and 18 nM, respectively. MGM-9 showed a potent opioid agonistic effect, and its effects were meditated by mu- and kappa-opioid receptor mechanisms in in vitro assays. Subcutaneous and oral administration of MGM-9 produced potent antinociceptive effects in mouse tail-flick, hot-plate, and writhing tests. When administered orally, the antinociceptive effect of MGM-9 was seven to 22 times more potent than that of morphine. The antinociceptive effects of MGM-9 were mediated by both mu- and kappa-opioid receptors. Subcutaneous administration of MGM-9 twice daily for 5 days led to antinociceptive tolerance. In the gastrointestinal transit study, MGM-9 inhibited gastrointestinal transit, but its effect was weaker than that of morphine at equi-antinociceptive doses. Furthermore, MGM-9 induced less hyperlocomotion and fewer rewarding effects than morphine. The rewarding effect of MGM-9 was blocked by a mu antagonist and enhanced by a kappa antagonist. Taken together, the results suggest that MGM-9 is a promising novel analgesic that has a stronger antinociceptive effect and weaker adverse effects than morphine.

Toward evidence-based prescribing at end of life: a comparative analysis of sustained-release morphine, oxycodone, and transdermal fentanyl, with pain, constipation, and caregiver interaction outcomes in hospice patients

OBJECTIVE

The primary goal of this investigation was to examine selected outcomes in hospice patients who are prescribed one of three sustained-release opioid preparations. The outcomes examined include: pain score, constipation severity, and ability of the patient to communicate with caregivers.

PATIENTS AND SETTINGS

This study included 12,000 terminally ill patients consecutively admitted to hospices and receiving pharmaceutical care services between the period of July 1 and December 31, 2002.

DESIGN

We retrospectively examined prescribing patterns of sustained-release morphine, oxycodone, and transdermal fentanyl. We compared individual opioids on the aforementioned outcome markers, as well as patient gender, terminal diagnosis, and median length of stay.

RESULTS

Patients prescribed a sustained-release opioid had similar average ratings of pain and constipation severity, regardless of the agent chosen. Patients prescribed transdermal fentanyl were reported to have more difficulty communicating with friends and family when compared with patients prescribed either morphine or oxycodone. On average, patients prescribed transdermal fentanyl had a shorter length of stay on hospice as compared with those receiving morphine or oxycodone.

CONCLUSION

There was no difference in observed pain or constipation severity among patients prescribed sustained-release opioid preparations. Patients receiving fentanyl were likely to have been prescribed the medication due to advanced illness and associated dysphagia. Diminished ability to communicate with caregivers and a shorter hospice course would be consistent with this profile. Further investigation is warranted to examine the correlation between a patient's ability to interact with caregivers and pain control achieved.

Involvement of mu-opioid receptors in antinociception and inhibition of gastrointestinal transit induced by 7-hydroxymitragynine, isolated from Thai herbal medicine Mitragyna speciosa

7-hydroxymitragynine, a constituent of the Thai herbal medicine Mitragyna speciosa, has been found to have a potent opioid antinociceptive effect. In the present study, we investigated the mechanism of antinociception and the inhibitory effect on gastrointestinal transit of 7-hydroxymitragynine, and compared its effects with those of morphine. When administered subcutaneously to mice, 7-hydroxymitragynine produced antinociceptive effects about 5.7 and 4.4 times more potent than those of morphine in the tail-flick (ED50=0.80 mg/kg) and hot-plate (ED50=0.93 mg/kg) tests, respectively. The antinociceptive effect of 7-hydroxymitragynine was significantly blocked by the mu1/mu2-opioid receptor antagonist beta-funaltrexamine hydrochloride (beta-FNA) and the mu1-opioid receptor-selective antagonist naloxonazine in both tests. Thus, 7-hydroxymitragynine acts predominantly on mu-opioid receptors, especially on mu1-opioid receptors. Isolated tissue studies further supported its specificity for the mu-opioid receptors. Further, 7-hydroxymintragynine dose-dependently (ED50=1.19 mg/kg, s.c.) and significantly inhibited gastrointestinal transit in mice, as morphine does. The inhibitory effect was significantly antagonized by beta-FNA pretreatment, but slightly antagonized by naloxonazine. The ED50 value of 7-hydroxymitragynine on gastrointestinal transit was larger than its antinociceptive ED50 value. On the other hand, morphine significantly inhibits gastrointestinal transit at a much smaller dose than its antinociceptive dose. These results suggest that mu-opioid receptor mechanisms mediate the antinociceptive effect and inhibition of gastrointestinal transit. This compound induced more potent antinociceptive effects and was less constipating than morphine.

Assessment of visceral pain-related pseudo-affective responses to colorectal distension in mice by intracolonic manometric recordings

Recently, a new manometric method has been proposed to quantify visceromotor responses (VMR) to colorectal distension (CRD) in rats. This method is based on monitoring pressure changes within the distending balloon during CRD. This study assesses the applicability of such a technique to the quantification of VMRs to CRD in mice. Electrical activity of the abdominal muscles and pressure changes within the distending balloon (mechanical response) were simultaneously recorded in conscious mice during CRD (phasic ascending, 10-80 mm Hg, or repetitive, 55 mm Hg). There was a clear stimulus-response relationship with a strong correlation between electrical and mechanical responses during the ascending (r(2) = 0.899, n = 7) or repetitive phasic CRD (r(2) = 0.926, n = 8). Repetitive phasic distensions (55 mm Hg) increased the mechanical and electrical responses by 71 +/- 20% and 42 +/- 16%, respectively (pulses 10-12 vs. 1-3; n = 8, both P < .01). Atropine (0.5 or 1 mg/kg, subcutaneously) did not affect the mechanical response to CRD. The mu-opioid agonist, fentanyl (0.05 mg/kg, subcutaneously), completely prevented the sensitizing response associated to repetitive distensions. These results show that noninvasive, surgery-free manometry of intracolonic pressure is a reliable method to assess VMRs to CRD in mice. The analgesic effect of compounds could be determined, indicating that the method can be used in pharmacologic studies.

PERSPECTIVE

The model presented to assess visceral pain in mice allows a broad use of this species in pharmacological studies and will be of use in the characterization of potential targets and new drugs for the treatment of human pathologies with visceral pain arising from the gut as a significant component.

Is the use of transdermal fentanyl inappropriate according to the WHO guidelines and the EAPC recommendations? A study of cancer patients in Italy

BACKGROUND

World Health Organization (WHO) guidelines, Agency for Health Care Policy and Research (AHCPR) clinical practice guidelines, and EAPC recommendations indicate oral route of opioid administration as the preferred route. Transdermal administration of opioids is considered an alternative when patients cannot take medications orally. Moreover, WHO and EAPC indicate orally administered morphine as the first-choice drug for the treatment of moderate to severe cancer-related pain. However, we can see that in Italy there is an increasing use of transdermal fentanyl (TF) as first-choice strong opioid (and route) even when oral administration of opioids is possible.

AIMS

The aims of this study are to describe the modality in the use of TF administration in two settings of care, taking into consideration (1) the drugs previously taken by the patients, (2) the reasons for switching from any drug to TF, (3) the conversion ratio used, and (4) the frequency of "inappropriate use of transdermal fentanyl according to the WHO guidelines and the EAPC recommendations", i.e., switching to fentanyl patch from any drug, even if there were no contraindications in using oral morphine. The settings of care considered were the out-patient palliative care unit (OP-PCU) and the oncological wards (OWs) of the National Cancer Institute (NCI) of Milan.

PATIENTS AND METHODS

The clinical charts of 98 patients prescribed with and given fentanyl patch for the first time at the NCI of Milan in 2002 were reviewed and the data gathered were grouped according to the administration of fentanyl at the OP-PCU (63 out-patients) or at the OWs (35 in-patients). Summary descriptive statistics and bar and box plots have been used. Fisher two-tailed exact text was applied to test the differences between in- and out-patients.

RESULTS

Before switching to TF, (1) in-patients were more frequently treated with nonsteroidal anti-inflammatory drugs (NSAIDs) and weak opioids (mostly tramadol) in respect to the out-patients (44.1 vs 25.8%) who were mostly treated with oral morphine (48.4 vs 20.6%) (p=0.045), and (2) 88.7% of the out-patients were treated with oral opioids and only 1.6% with parenteral opioids in respect to OWs where 69.7% were on oral opioids and 18.2% on parenteral opioids (p=0.006). In 29% of out-patients and in 53% of in-patients, changing to fentanyl patch was considered as "inappropriate" (p=0.028) according to the WHO guidelines and the EAPC recommendations. No statistically significant differences between the two settings were observed regarding the reasons for switching and the conversion ratio used.

CONCLUSIONS

There is a trend to use fentanyl patch as first-choice strong opioid in cancer patients in situations such as titration phase, in the presence of instable pain, and in the absence of dysphagia or gastrointestinal symptoms where the use of oral morphine is, however, not contraindicated.

Single opioid administration modifies gonadal steroids in both the CNS and plasma of male rats

While morphine remains one of the most widely used opioids for the treatment of painful conditions, other opioids are also commonly employed. Because of the interactions between opioids and gonadal hormones, in particular opioid-induced hypogonadism, this study investigated the effects of widely used opioids on plasma testosterone and estradiol levels and brain testosterone levels in male rats. Animals were s.c. injected with two concentrations of morphine (5 or 10 mg/kg), fentanyl (0.05 or 0.1 mg/kg), tramadol (10 or 40 mg/kg), buprenorphine (0.05 or 0.1 mg/kg) or saline (0.7 ml/kg). Four or 24 h after treatment, the rats were deeply anesthetized to collect blood samples from the abdominal aorta and to perfuse the brains with saline. Plasma and brain hormone levels were measured by radioimmunoassay. In rats studied 4 h after treatment, all the opioids except tramadol 10 mg/kg decreased plasma testosterone in comparison with saline administration. At the same time, plasma estradiol levels were lower than control in the groups treated with the low doses of morphine, tramadol and buprenorphine, while estradiol remained at control levels in the other groups. Twenty-four hours after treatment, plasma testosterone levels were different (higher) than control in the animals treated with the low doses of morphine, fentanyl and buprenorphine. Estradiol was lower than control in the low dose groups, while the high doses did not produce any changes with respect to control. Four hours after treatment, brain testosterone was drastically decreased in all groups except buprenorphine, in which it remained at control levels. All groups returned to control levels at 24 h after treatment. In conclusion, opioids exert important effects on plasma and CNS sex hormone levels. The different magnitude and time-course of the effects of the different opiates on testosterone and estradiol levels are likely due to their different mechanism of action.

Evaluation of pseudo-affective responses to noxious colorectal distension in rats by manometric recordings

Recordings of electromyographic (EMG) activity in the abdominal musculature are generally used to quantify the pseudo-affective visceromotor response induced by colorectal distension (CRD) in rodents. The present study describes a non-invasive, manometric method to quantify the magnitude of the abdominal contractions evoked by CRD. CRD-induced increases in EMG activity in female rats (electrical response) were compared to phasic changes in balloon pressure (mechanical response). A phasic increasing CRD paradigm from 10 to 80mmHg with 10mmHg intervals induced a clear stimulus-response relationship with a strong correlation (r(2)=0.93) between the electrical and mechanical responses. Twelve repeated phasic distensions at 80mmHg increased the mechanical response by 133+/-53% (P<0.01), while the electrical response only increased by 20+/-19% (P>0.05), when comparing the last distension to the first. Atropine methyl bromide (1mg/kg, i.v.) did not affect the mechanical response to distension at 80mmHg, suggesting that colonic activity per se, does not contribute to the balloon pressure variations during CRD in the current experimental set-up. The mu-opioid receptor agonist fentanyl at a dose of 1.5microg/kg (i.v.) significantly reduced the mechanical response to CRD (P<0.01) while the electrical response was not affected. The present study shows that phasic bursts in EMG activity from the abdominal musculature occur simultaneously with balloon pressure variations, which may represent a non-invasive alternative to EMG recordings. Furthermore, the mechanical response is a more sensitive parameter for detecting both hyperalgesic and analgesic responses.

The role of opioids in cancer pain

Columba Quigley, as a specialist in palliative medicine, works in a hospital based support team. She also works with a community based palliative care team and in a hospice, where patients are admitted for terminal care, respite, and control of symptoms. Pain occurs often in patients with cancer, particularly those with advanced disease. In addition, pain is one of the most feared symptoms in people with a diagnosis of cancer. Using analgesics (particularly opioids) appropriately effectively controls cancer pain in most patients

A Comparison of the Antinociceptive and Adverse Effects of the mu-Opioid Agonist Morphine and the delta-Opioid Agonist SNC80

delta-Opioid receptor agonists have been postulated to induce analgesia without the adverse effects commonly associated with mu-opioids e.g. morphine. In the present study, we evaluated the occurrence of antinociceptive and opioid-like side effects in rats (n=5-7) treated with a single dose of subcutaneous morphine (0.01 to 40 mg/kg) or SNC80 (0.63 to 80 mg/kg). The antinociceptive effects of morphine and SNC80 were compared using a range of nociceptive tests including the tail withdrawal test, the acetic acid-induced abdominal constriction (writhing) assay, the automated formalin test and a model of inflammation-induced thermal hyperalgesia. The adverse effects of both drugs were examined in animal models for gastrointestinal (GI) inhibition (charcoal test; ricinus oil test), respiratory depression (blood-gas analysis), motor disturbances (automated rotarod model) and abuse liability (drug discrimination learning). Morphine displayed significant antinociceptive and adverse effects in all the animal models employed. SNC80 exhibited a significant effect in the writhing test and limited efficacy in a model of inflammation-induced thermal hypersensitivity. A delay in the occurrence of diarrhoea and some limited increases in PCO(2) were observed with the higher doses of SNC80 (> or =40 mg/kg). In conclusion, the delta-opioid agonist SNC80 lacks both the analgesic efficacy and adverse effects of mu-opioids. However, the activity of SNC80 in the inflammatory model suggests delta-opioid agonists may be useful analgesics in the treatment of some forms of inflammatory pain.

Stark wirksame Opioidanalgetika und Obstipation

In cancer pain therapy treatment with strong opioids is essential. However, it may be accompanied by the occurrence of various adverse effects. The most frequent and persistent side effect in the course of opioid treatment is constipation. It is mainly caused by linkage of the opioid to the peripheral mu-receptors in the bowel and may increase as a result of certain concomitant circumstances, such as poor intake of fluids or electrolyte disorder. Present research indicates that there is a relation between type of opioid and degree of constipation, i.e. treatment with transdermal fentanyl or methadone tends to cause less constipation compared to morphine or hydromorphone. The route of administration of morphine--oral vs. subcutaneous--does not seem to affect the incidence of opioid-induced constipation. Furthermore, prophylaxis and efficient control of opioid-induced constipation still fail to be part of the routine in pain treatment.

Emerging analgesics in cancer pain management

Cancer pain is one of the most frequent symptoms in malignant disease, severely impairing the patients' quality of life. The recommendations of the World Health Organization will provide adequate pain relief for the vast majority of cancer patients. However, some patients will suffer from inadequate analgesia or intolerable side effects. Cyclooxygenase-2 (COX-2)-selective non-steroidal anti-inflammatory drugs (NSAIDs), new anticonvulsants, cannabinoids and NMDA receptor antagonists are being developed for these patients. NSAIDs with nitric oxide-releasing moieties are an interesting addition, as this new class of analgesics combines improved analgesic efficacy with higher tolerability. Conotoxins and other drugs such as nicotinic acetylcholinergic receptor agonists will be advantageous only for a few patients in the near future, as side-effect profile and risk of complications, as well as the burden on the patient, often are not worth the additional analgesic benefit.

Opioid purchases and expenditure in nine western European countries: 'are we killing off morphine?'

BACKGROUND

In clinical practice the major role of opioid drugs is the management of malignant and nonmalignant pain. The primary aim of this study is to evaluate the trend in sales of four opioid analgesic drugs (codeine, tramadol, morphine, fentanyl), from wholesalers to community pharmacies, as an indicator of opioid consumption in nine European countries in 2001, 2002 and 2003. Secondary aims are to compare: (a) the amount of each drug purchased by different countries in 2003; (b) the average price for each drug in the different countries in 2003; and (c) the total expenditure for each opioid from 2001 to 2003.

METHODS

Data from the Statistical Report on drugs purchased by pharmacies was supplied by IMS Health, an internationally accepted information provider for the pharmaceutical and health care industries.

FINDING

In the period 2001 2003, while the percentage increase of purchases of fentanyl and tramadol was considerable, that of morphine was the lowest in most of the nine countries. The largest consumer of codeine was the UK and of tramadol was Belgium. The consumption of morphine was the lowest reported in all the countries together and was three times lower than that of transdermal fentanyl. There was a high variability in the costs of the opioids among the different countries. In 2003, the total expenditure for fentanyl reached the highest total expenditure [corrected] followed by codeine. Morphine presents the lowest expenditure in all nine countries and over all three years.

INTERPRETATION

These results open up many questions. What factors influence opioid purchasing and costs in these European countries? It would be interesting to have the answers from those people who know the actual situation in the individual countries.

A preclinical comparison between different opioids: antinociceptive versus adverse effects

Reduced side-effect liability of opioids may enhance the patient's quality of life and decrease the incidence of opioid-insensitive pain. Literature offers few comparative data between different opioids at equianalgesic doses. Therefore morphine, fentanyl, buprenorphine, codeine, hydrocodone and oxycodone were compared for analgesic properties and side-effect profiles in rats. Analgesic efficacy was analysed using a tail withdrawal test for acute thermal nociception, a formalin test for chemically induced inflammatory pain and a von Frey test for mechanical hypersensitivity. For side-effect profiling inhibition of gastrointestinal activity was evaluated in a charcoal and ricinus oil test, arterial PCO(2) was determined for measuring respiratory depression, the discriminative stimulus properties linked to the narcotic cue were assessed using a drug discrimination learning test, and motor coordination was tested through rotarod performance. ED(50)'s for the occurrence of side-effects were compared to ED(50)'s in behavioural pain tests. Fentanyl had a strong analgesic potency and, compared to other opioids, an acceptable side-effect profiling at analgesic ED(50)'s. Also consistent was the ceiling effect of buprenorphine implying an increased safety margin for side-effects, but a decreased analgesic efficacy. Differences between opioids as observed in this study can have important indications for their use in acute as well as in the onset of chronic treatments.

Efficacy and safety of transdermal fentanyl and sustained-release oral morphine in patients with cancer and chronic non-cancer pain

PURPOSE

To evaluate effectiveness and safety information of transdermal fentanyl (TDF) (Duragesic/Durogesic) and sustained-release oral morphine (SRM) in cancer pain (CP) and chronic non-cancer pain (NCP), a pooled analysis was conducted on datasets of published, open label, uncontrolled (no comparator group) and randomised controlled (with SRM as comparator) studies of TDF.

PATIENTS AND METHODS

Eight trials with treatment durations of at least 28 days met the inclusion criteria. The effectiveness analysis assessed changes in average pain and pain 'right now' scores between baseline and Day 28. The safety analysis evaluated the incidence of adverse events (AEs) reported within the first 28 days of treatment with TDF or SRM. Subgroup analyses included pain type, gender, age, weight, and body mass index.

RESULTS

Pooled efficacy data were available from 1220 patients; these showed that both TDF and SRM were effective in improving pain 'right now' scores (0-100 scale) from baseline to Day 28. The improvement was significantly more pronounced in the TDF treatment group (-26.7 +/- 31.3 for TDF, -18.7 +/- 30.9 for SRM, p = 0.002). This favourable effect of TDF was most apparent amongst patients with NCP. Data concerning AEs were available from over 2500 patients with CP (3 out of 10 patients) or chronic NCP (7 out of 10 patients). Significantly fewer patients in the TDF than in the SRM group reported any AE (72% vs. 87% respectively; p < 0.001), or an AE leading to the study drug being permanently discontinued (16% vs. 23% respectively; p < 0.001). Constipation and somnolence occurred considerably less frequently in the TDF than in the SRM treatment group. This difference was statistically significant in both the CP and NCP subgroups.

CONCLUSION

This pooled data analysis provides expanded insight into the safety and effectiveness profile of transdermal fentanyl in patients with chronic pain. It shows significantly improved pain relief with transdermal fentanyl compared with sustained-release oral morphine, and supports current evidence of favourable tolerability of transdermal fentanyl, particularly with regard to reduced constipation and somnolence.

Incidence of constipation associated with long-acting opioid therapy: a comparative study

BACKGROUND

Opioid therapy plays a key role in the management of chronic pain. Constipation is one of the more frequently occurring adverse effects associated with opioid therapy.

METHODS

A retrospective cohort design study was conducted to determine the incidence of constipation in chronic pain patients who received three different long-acting opioids (transdermal fentanyl, oxycodone HCl controlled-release [CR], or morphine CR) for malignant or nonmalignant chronic pain. The data source was claims data (January 1996 through March 2001) from a 20% random sample of the California Medicaid (Medi-Cal) database. Claims data were from adult patients with chronic pain (malignant or nonmalignant) who had no prior diagnosis of constipation and no prior usage of long-acting opioids for at least 3 months before the observation period. Patients were followed for at least 3 months after the initiation of opioid therapy. ICD-9 code for diagnosis of constipation was the main outcome variable. Crude rates of constipation, annual incidence density, relative risk, and adjusted odds ratios were compared.

RESULTS

A total of 1,836 patients (601 receiving transdermal fentanyl, 721 receiving oxycodone CR, and 514 receiving morphine CR) were included in the analysis. Crude (unadjusted) rates of constipation were 3.7% for transdermal fentanyl, 6.1% for oxycodone CR, and 5.1% for morphine CR (P > 0.05). Transdermal fentanyl had a lower annual incidence density and risk of constipation than oxycodone CR and morphine CR (P > 0.05). After adjusting for confounding variables, including race and supplemental opioid use, the adjusted risk of constipation was 78% greater in the oxycodone CR group (P = 0.0337) and 44% greater in the morphine CR group (P = 0.2242) than in the transdermal fentanyl group.

CONCLUSION

In this population, patients receiving transdermal fentanyl had a lower risk of developing constipation compared with those receiving oxycodone CR or morphine CR.

Evaluation of long-term efficacy and safety of transdermal fentanyl in the treatment of chronic noncancer pain

The objective of this international, multicenter, open-label trial was to assess the efficacy and safety of up to 12 months of therapy with transdermal therapeutic system (TTS) fentanyl in patients (n = 532) with chronic noncancer pain. The trial was completed by 301 (57%) of the patients. The main outcome measures were pain control assessment, global treatment satisfaction, patient preference for TTS fentanyl, and quality of life. The mean dose of transdermal fentanyl (TDF) increased from 48 to 90 microg/h during a period of 12 months. During treatment, on average 67% of patients within the efficacy analysis group (n = 524) reported very good, good, or moderate pain control. Global satisfaction (very good or good) was also stable at 42%. The majority (86%) of patients reported a preference for TDF over their previous treatment (P < .001, binomial test). Short Form 36 quality-of-life scores improved from baseline for bodily pain. The most frequent treatment-related adverse events were nausea (31%), constipation (19%), and somnolence (18%). With regard to opioid-specific adverse events (respiratory depression [< 1%], adrenal insufficiency [< 1%], drug abuse/dependence [1%], and opioid withdrawal syndrome [3%]), these were extremely rare and, with the exception of opioid withdrawal syndrome, none was considered definitively related to the treatment. Long-term treatment with TDF provided a stable degree of pain control in the majority of patients with moderate to severe chronic noncancer pain. It was preferred by the majority of patients compared with their previous opioid medication. Overall, long-term treatment with TDF was generally well tolerated, particularly in view of the low incidence of potentially serious side effects such as drug abuse/dependence and respiratory depression. However, at present, it is important that patients receiving TDF should still be subject to careful assessment and monitoring.

Effect of fentanyl on 5-HT efflux involves both opioid and 5-HT1A receptors

1. Fentanyl is a micro -opioid analgesic that might disinhibit 5-HT neurons and thus increase 5-HT efflux. However, fentanyl also binds to 5-HT(1A) receptors, and if it activates 5-HT(1A) somatodendritic autoreceptors, the resultant inhibition might offset opioid-mediated increases in 5-HT efflux. To test this hypothesis, we used microdialysis to study effects of fentanyl on extracellular 5-HT in the dorsal raphe nucleus (DRN) of unanesthetized rats. 2. Systemic administration of fentanyl (0.01-0.2 mg kg(-1), s.c.) increased 5-HT efflux in the DRN. An intermediate dose of fentanyl (0.05 mg kg(-1)) produced the maximum increase in 5-HT to approximately 180% of baseline levels in the DRN. Naltrexone (10 mg kg(-1), s.c.) blocked the increase in response to systemic fentanyl (0.05 mg kg(-1)). 3. In contrast, during infusion into the DRN, fentanyl (10-1000 micro M) induced a dose-dependent decrease in 5-HT. Naltrexone and nor-binaltorphimine failed to block the decrease suggesting that micro - and kappa-opioid receptors did not mediate this effect. 4. Systemic (-)-pindolol (8 mg kg(-1), s.c.) or infusion of WAY-100635 (100 micro M) into the DRN blocked the decrease, and instead 5-HT increased in response to local infusion of fentanyl (100 micro M). WAY-100635 (0.3 mg kg(-1), s.c.) also potentiated the effect of systemic fentanyl (0.2 mg kg(-1), s.c.). (-)-Pindolol and WAY-100635 block 5HT(1A) receptors, indicating that inhibition of 5-HT neuronal activity resulting from fentanyl binding to somatodendritic autoreceptors attenuated opioid-mediated increases in 5-HT efflux. 5. These results provide novel evidence that besides stimulating micro -opioid receptors, fentanyl is a 5-HT(1A) receptor agonist. Possibly, this contributes to lethality of fentanyl overdose.

Is opiate compliance a problem in cancer pain? A survey of health-care professionals' views

This article reports on a questionnaire survey, which was conducted among health-care professionals to investigate their experience of opiate compliance in terminally ill patients with cancer pain. There were 93 respondents, ranging from hospital consultants to junior doctors and specialist nurses to staff nurses. Sixty-six respondents (71%) indicated that non-compliance was a problem in pain control. Non-compliance was considered a problem in more than 15% of patients for 92 respondents. Non-compliance was reported for all the routes and types of strong opiates. Short-acting morphine administered every 4-6 hours was reported as the drug most likely not to be taken (n=52, 55.9%), whereas transdermal opiates were the most common second-line choice for non-compliant patients (n=65, 70%). Participants indicated that the reasons for non-compliance varied and included gastrointestinal and CNS side effects, fear of addiction and lack of help with drug.

Palliative care of the chronically critically ill patient

Evidence is accumulating that distressing physical and emotional symptoms are prevalent among patients with critical illness, including those requiring prolonged mechanical ventilation, and that suffering is underestimated and undertreated by caregivers. Although patients and their families rank communication as a preeminent concern, it remains deficient in process and content, even when the illness requires weeks of critical care. Strategies are available to improve symptom management and communication about appropriate goals of care. For the CCI, whose risks of death, disability, and suffering are so high, it is essential that excellent palliative care be provided along with restorative treatment in an integrated way.

Transdermal fentanyl: an updated review of its pharmacological properties and therapeutic efficacy in chronic cancer pain control

Fentanyl is a synthetic opioid agonist which interacts primarily with the mu-opioid receptor. The low molecular weight, high potency and lipid solubility of fentanyl make it suitable for delivery by the transdermal therapeutic system. These patches are designed to deliver fentanyl at a constant rate (25, 50, 75 and 100 microg/h), and require replacement every 3 days. Data from randomised, nonblind trials suggest that transdermal fentanyl is as effective as sustained-release oral morphine in the treatment of chronic cancer pain, as reported by patients using visual and numerical analogue scales as well as verbal description scales. No obvious differences in health-related quality of life were found in patients with chronic cancer pain when comparing transdermal fentanyl with sustained-release oral morphine. Nevertheless, significantly more patients expressed a preference for transdermal fentanyl than for sustained-release oral morphine after a randomised, nonblind, crossover trial. Because of the formation of a fentanyl depot in the skin tissue, serum fentanyl concentrations increase gradually following initial application, generally levelling off between 12 and 24 hours. Thereafter, they remain relatively constant, with some fluctuation, for the remainder of the 72-hour application period. Once achieved, steady-state plasma fentanyl concentrations can be maintained for as long as the patches are renewed. The most frequently observed adverse events during transdermal fentanyl administration (as with other opioid agonists) included vomiting, nausea and constipation. Data from a nonblind, randomised trials suggest that constipation occurs less frequently in patients receiving transdermal fentanyl than in those given sustained-release oral morphine. The most serious adverse event reported in US premarketing trials was hypoventilation, which occurred with an incidence of approximately 2%. Adverse reactions related to skin and appendages (i.e. rash and application site reactions - erythema, papules, itching and oedema) were reported in 153 patients with cancer at a frequency between 1 and 3%.

CONCLUSION

Transdermal fentanyl is a useful opioid-agonist for the treatment of moderate to severe chronic cancer pain. The advantages of transdermal fentanyl include ease of administration and the 3-day application interval. These factors coupled with a lower incidence of constipation are likely to contribute to the reported patient preference of transdermal fentanyl over sustained-release oral morphine.

Strategies for the treatment of cancer pain in the new millennium

As was the case in the era before us, in the new millennium we will continue to see an abundance of patients experiencing cancer-related pain for different reasons. Although much needless pain and suffering still affects many of those with cancer, we are presented with a medical dichotomy. With the analgesic drugs available today, and the relatively simple and effective guidelines to treat cancer pain published and disseminated by the World Health Organization, why do people with cancer continue to experience pain? As we search for the answer, the horizon may hold promising new drugs, 'old drugs' with new interest and applications, and new strategies for the field of pain therapy. Possibilities include the isolation and development of analgesics or analgesic combinations that may minimise the adverse effects which are often associated with the current therapeutic class of opioid analgesics. In addition, current research points to promising results identifying the N-methyl D-aspartate non-opioid receptor as a likely component of neuropathic pain. Drugs such as gabapentin, the mechanism of action of which is not well known, have found favour within the clinical community for their analgesic properties and good tolerability. Methadone, in a phase of resurgence, has garnered the attention of the clinical community because of its unique receptor activity and pharmacoeconomic benefits. A number of clinical studies have demonstrated that methadone has a valuable role in treating cancer pain. Perhaps, an unbalanced focus on the risks of inappropriate use, rather than the benefits, should not compromise or distract from the use of methadone as an alternative to morphine. Studies are on going to assess the potential role of methadone in treating neuropathic pain. Drugs such as cannabinoids, although currently applicable for patients with anorexia, nausea and/or vomiting, may offer benefits to patients experiencing pain. Other opportunities exist with such compounds as alpha2-adrenergic agonists, nicotine, lidocaine and ketamine. New strategies such as the switching opioids and/or their route of administration may offer improved analgesia with fewer adverse effects, thus providing therapeutic alternatives for the clinical community. In addition, there is interest in the co-administration of opioids that act on different receptors. For instance, oxycodone appears to be a kappa opioid receptor agonist and may offer enhanced analgesia when combined with morphine.

Randomised crossover trial of transdermal fentanyl and sustained release oral morphine for treating chronic non-cancer pain

OBJECTIVES

To compare patients' preference for transdermal fentanyl or sustained release oral morphine, their level of pain control, and their quality of life after treatment.

DESIGN

Randomised, multicentre, international, open label, crossover trial.

SETTING

35 centres in Belgium, Canada, Denmark, Finland, the United Kingdom, the Netherlands, and South Africa.

PARTICIPANTS

256 patients (aged 26-82 years) with chronic non-cancer pain who had been treated with opioids.

MAIN OUTCOME MEASURES

Patients' preference for transdermal fentanyl or sustained release oral morphine, pain control, quality of life, and safety assessments.

RESULTS

Of 212 patients, 138 (65%) preferred transdermal fentanyl, whereas 59 (28%) preferred sustained release oral morphine and 15 (7%) expressed no preference. Better pain relief was the main reason for preference for fentanyl given by 35% of patients. More patients considered pain control as being "good" or "very good" with fentanyl than with morphine (35% v 23%, P=0.002). These results were reflected in both patients' and investigators' opinions on the global efficacy of transdermal fentanyl. Patients receiving fentanyl had on average higher quality of life scores than those receiving morphine. The incidence of adverse events was similar in both treatment groups; however, more patients experienced constipation with morphine than with fentanyl (48% v 29%, P<0.001). Overall, 41% of patients experienced mild or moderate cutaneous problems associated with wearing the transdermal fentanyl patch, and more patients withdrew because of adverse events during treatment with fentanyl than with morphine (10% v 5%). However, within the subgroup of patients naive to both fentanyl and morphine, similar numbers of patients withdrew owing to adverse effects (11% v 10%, respectively).

CONCLUSION

Transdermal fentanyl was preferred to sustained release oral morphine by patients with chronic non-cancer pain previously treated with opioids. The main reason for preference was better pain relief, achieved with less constipation and an enhanced quality of life.

Morphine and alternative opioids in cancer pain: the EAPC recommendations

An expert working group of the European Association for Palliative Care has revised and updated its guidelines on the use of morphine in the management of cancer pain. The revised recommendations presented here give guidance on the use of morphine and the alternative strong opioid analgesics which have been introduced in many parts of the world in recent years. Practical strategies for dealing with difficult situations are described presenting a consensus view where supporting evidence is lacking. The strength of the evidence on which each recommendation is based is indicated.

Constipation and the use of laxatives: a comparison between transdermal fentanyl and oral morphine

Constipation and the use of laxatives were investigated in patients with chronic cancer pain treated with oral morphine and transdermal fentanyl in an open sequential trial. Forty-six patients were treated with slow-release morphine 30-1000 mg/day for 6 days and 39 of these patients were switched to transdermal fentanyl 0.6-9.6 mg/day with a conversion ratio of 100:1. Median fentanyl doses increased from 1.2 to 3.0 mg/day throughout the 30-day transdermal treatment period. Twenty-three patients completed the study. Two patients died from the basic disease while treated with transdermal fentanyl, 12 patients were excluded for various reasons, and not enough data for evaluation were available for two patients. Mean pain intensity decreased slightly after conversion although the number of patients with breakthrough pain or requiring immediate-release morphine as a rescue medication was higher with transdermal fentanyl. The number of patients with bowel movements did not change after the opioid switch but the number of patients taking laxatives was reduced significantly from 78-87% of the patients per treatment day (morphine) to 22-48% (fentanyl). Lactulose was used mainly and was reduced most drastically, but other laxatives were also used less frequently. In this study transdermal fentanyl was associated with a significantly lower use of laxatives compared to oral morphine. The difference in the degree of constipation between the two analgesic regimens should be confirmed in a randomized double-blind study that takes into account both constipation and use of laxatives.

Clinical pharmacokinetics of transdermal opioids: focus on transdermal fentanyl

Transdermal delivery allows continuous systemic application of opioids through the intact skin. This review analyses the pharmacokinetic properties of transdermal opioid administration in the context of clinical experience, with a focus on fentanyl. A transdermal therapeutic system (TTS) for fentanyl has been developed. The amount of fentanyl released is proportional to the surface area of the TTS, which is available in different sizes. After the first application of a TTS, a fentanyl depot concentrates in the upper skin layers and it takes several hours until clinical effects are observed. The time from application to minimal effective and maximum serum concentrations is 1.2 to 40 hours and 12 to 48 hours, respectively. Steady state is reached on the third day, and can be maintained as long as patches are renewed. Within each 72-hour period, serum concentrations decrease gradually over the second and third days. When a TTS is removed, fentanyl continues to be absorbed into the systemic circulation from the cutaneous depot. The terminal half-life for TTS fentanyl is approximately 13 to 25 hours. The interindividual variability of serum concentrations, partly caused by different clearance rates, is markedly larger than the intraindividual variability. The effectiveness of TTS fentanyl was first demonstrated in acute postoperative pain. However, the slow pharmacokinetics and large variability of TTS fentanyl, together with the relatively short duration of postoperative pain, precluded adequate dose finding and led to inadequate pain relief or, especially, a high incidence of respiratory depression; such use is now contraindicated. Conversely, in cancer pain, TTS fentanyl offers an interesting alternative to oral morphine, and its effectiveness and tolerability in this indication has been demonstrated by a number of trials. Its usefulness in chronic pain of nonmalignant origin remains to be confirmed in controlled trials. In general, TTS fentanyl produces the same adverse effects as other opioids, mainly sedation, nausea, vomiting and constipation. In comparison with oral morphine, TTS fentanyl causes fewer gastrointestinal adverse events. The risk of hypoventilation is comparatively low in cancer patients. Sufentanil and buprenorphine may also be suitable for transdermal delivery, but clinical results are not yet available. Transdermal morphine is only useful if applied to de-epithelialised skin. However, iontophoresis may allow transdermal administration of opioids, including morphine, with a rapid achievement of steady state concentrations and the ability to adjust delivery rates. This would be beneficial for acute and/or breakthrough pain, and initial clinical trials are in progress.

Reduction in constipation and laxative requirements following opioid rotation to methadone: a report of four cases

Constipation is a common symptom in cancer patients, especially in those who are receiving opioid analgesics for pain. Although several articles have recently examined constipation with respect to causation and treatment, little research has been done to elucidate the effects of different opioids on the bowel. Recent research has found that laxative doses may be lower in patients using methadone as an analgesic, but changes in constipation were not measured. We report here on four cases in which patients had improvement in constipation and decreased laxative requirements following opioid rotation to methadone.