Alternative opioids to morphine in palliative care: a review of current practice and evidence

Apneic response to fentanyl in adult rats: Role of laryngeal afferents

Intravenous (systemic) bolus injection of fentanyl (FNT) reportedly induces an immediate vagal-mediated apnea; however, the precise origin of vagal afferents responsible for this apnea remains unknown. We tested whether intralaryngeal (local) application of FNT would also trigger an apnea and whether the apneic response to both local and systemic administration of FNT was laryngeal afferent-mediated. Cardiorespiratory responses to FNT were recorded in anesthetized male adult rats with and without bilateral sectioning of the superior laryngeal nerve (SLNx) or peri-SLN capsaicin treatment (SLNcap) to block local C-fiber signal conduction. Opioid mu-receptor (MOR)-immunoreactivity was detected in laryngeal C- and myelinated neurons. We found that local and systemic administration of FNT elicited an immediate apnea. SLNx, rather than SLNcap, abolished the apneic response to local FNT application though MORs were abundantly expressed in both laryngeal C- and myelinated neurons. Importantly, SLNx failed to affect the apneic response to systemic FNT administration. These results lead to the conclusion that laryngeal afferents' MORs are responsible for the apneic response to local, but not systemic, administration of FNT.

Pharmacokinetics, adverse effects and effects on thermal nociception following administration of three doses of codeine to horses

BACKGROUND

In humans, codeine is a commonly prescribed analgesic that produces its therapeutic effect largely through metabolism to morphine. In some species, analgesic effects of morphine have also been attributed to the morphine-6-glucuronide (M6G) metabolite. Although an effective analgesic, administration of morphine to horses produces dose-dependent neuroexcitation at therapeutic doses. Oral administration of codeine at a dose of 0.6 mg/kg has been shown to generate morphine and M6G concentrations comparable to that observed following administration of clinically effective doses of morphine, without the concomitant adverse effects observed with morphine administration. Based on these results, it was hypothesized that codeine administration would provide effective analgesia with decreased adverse excitatory effects compared to morphine. Seven horses received a single oral dose of saline or 0.3, 0.6 or 1.2 mg/kg codeine or 0.2 mg/kg morphine IV (positive control) in a randomized balanced 5-way cross-over design. Blood samples were collected up to 72 hours post administration, codeine, codeine 6-glucuronide, norcodeine morphine, morphine 3-glucuronide and M6G concentrations determined by liquid chromatography- mass spectrometry and pharmacokinetic analysis performed. Pre- and post-drug related behavior, locomotor activity, heart rate and gastrointestinal borborygmi were recorded. Response to noxious stimuli was evaluated by determining thermal threshold latency.

RESULTS

Morphine concentrations were highest in the morphine dose group at all times post administration, however, M6G concentrations were significantly higher in all the codeine dose groups compared to the morphine group starting at 1 hour post drug administration and up to 72-hours in the 1.2 mg/kg group. With the exception of one horse that exhibited signs of colic following administration of 0.3 and 0.6 mg/kg, codeine administration was well tolerated. Morphine administration, led to signs of agitation, tremors and excitation. There was not a significant effect on thermal nociception in any of the dose groups studied.

CONCLUSIONS

The current study describes the metabolic profile and pharmacokinetics of codeine in horses and provides information that can be utilized in the design of future studies to understand the anti-nociceptive and analgesic effects of opioids in this species with the goal of promoting judicious and safe use of this important class of drugs.

Metabolism, pharmacokinetics and selected pharmacodynamic effects of codeine following a single oral administration to horses

OBJECTIVE

To describe the pharmacokinetics and selected pharmacodynamic variables of codeine and its metabolites in Thoroughbred horses following a single oral administration.

STUDY DESIGN

Prospective experimental study.

ANIMALS

A total of 12 Thoroughbred horses, nine geldings and three mares, aged 4-8 years.

METHODS

Horses were administered codeine (0.6 mg kg-1) orally and blood was collected before administration and at various times until 120 hours post administration. Plasma and urine samples were collected and analyzed for codeine and its metabolites by liquid chromatography-mass spectrometry, and plasma pharmacokinetics were determined. Heart rate and rhythm, step counts, packed cell volume and total plasma protein were measured before and 4 hours after administration.

RESULTS

Codeine was rapidly converted to the metabolites norcodeine, codeine-6-glucuronide (C6G), morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). Plasma codeine concentrations were best represented using a two-compartment model. The Cmax, tmax and elimination t½ were 270.7 ± 136.0 ng mL-1, 0.438 ± 0.156 hours and 2.00 ± 0.534 hours, respectively. M3G was the main metabolite detected (Cmax 492.7 ± 35.5 ng mL-1), followed by C6G (Cmax 96.1 ± 33.8 ng mL-1) and M6G (Cmax 22.3 ± 4.96 ng mL-1). Morphine and norcodeine were the least abundant metabolites with Cmax of 3.17 ± 0.95 and 1.42 ± 0.79 ng mL-1, respectively. No significant adverse or excitatory effects were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Following oral administration, codeine is rapidly metabolized to morphine, M3G, M6G, C6G and norcodeine in horses. Plasma concentrations of M6G, a presumed active metabolite of morphine, were comparable to concentrations reported previously following administration of an analgesic dose of morphine to horses. Codeine was well tolerated based on pharmacodynamic variables and behavioral observations.

Opioid Prescribing Patterns Before and After an Inpatient Palliative Care Consultation

BACKGROUND

To the best of our knowledge, the change in opioid prescription patterns upon referral to a palliative care team (PCT) was not previously investigated in the Middle East.

OBJECTIVE

This study aimed to explore the change in the pattern of opioid prescription and the pain scores before and after referring inpatients to a PCT.

METHODS

We conducted a retrospective review of patients' records including all inpatients ≥15 years newly referred to the PCT over a period of 21 months at King Faisal Specialist Hospital and Research Center, Riyadh.

RESULTS

Of 631 patients, 52.3% were females, the median age was 54 years, and 96.7% had cancer. The proportion of patients on opioids before referral (83.4%) increased to 93.3% in the postreferral period, P < .0001. Patients receiving opioids on a regular basis increased from 31.9% before referral to 49.9% after referral to the PCT, P < .0001. Morphine was the most commonly prescribed opioid on a regular basis pre- and postreferral. Upon referral, the administration of opioids through the subcutaneous route increased from 3.7% to 10.9%, P < .0001. On average, pain scores were reduced by 1 point on a 0 to 10 numeric scale within 48 hours of seeing a patient by the PCT, P < .0001.

CONCLUSION

Patients referred to a PCT are likely to get their opioid prescription optimized and pain scores improved shortly after the PCT involvement. Patients with cancer-related pain requiring opioids should be referred to a PCT as early as possible.

Characterization of the in vitro CYP450 mediated metabolism of the polymorphic CYP2D6 probe drug codeine in horses

Despite their widespread popularity as sport and companion animals and published and anecdotal reports of vast difference in drug disposition and pharmacokinetics between individuals, studies describing equine drug metabolism are limited. It has been theorized that similar to humans, members of the CYP2D family in horses may be polymorphic in nature leading to differences in metabolism of substrates. This study aims to build on the limited current knowledge regarding P450 mediated metabolism in horses by describing the metabolism of the polymorphic CYP2D6 probe drug codeine in vitro. Codeine, at varying substrate concentrations, was incubated with equine liver microsomes (±UDPGA) and a panel of baculovirus expressed recombinant equine P450s. Parent drug and metabolite concentrations were determined using LC-MS/MS. Incubation of codeine in equine liver microsomes generated norcodeine, morphine, codeine glucuronide and morphine 3- and 6- glucuronide. In recombinant P450 assays, the newly described CYP2D82 was responsible for catalyzing the biotransformation of codeine to morphine (K_m of 247.4 μM and a V_max of 1.6 pmol/min/pmol P450). CYP2D82 is 80% homologous to the highly polymorphic CYP2D6 enzyme, which is responsible for biotransformation of codeine to morphine in humans. CYP3A95, which shares 79% sequence homology with human CYP3A4 and CYP2D50 catalyzed the conversion of codeine to norcodeine (K_m of 104.1 and 526.9 μM, V_max of 2.8 and 2.6 pmol/min/pmol P450). In addition to describing the P450 mediated metabolism of codeine, the current study offers a candidate probe drug that could be used in vivo to study the functional implications of polymorphisms in the CYP2D gene in horses.

Head and Neck Cancer Pain

Pain is a significant morbidity resulting from head and neck cancer. Pain may also be the result of the treatments directed against head and neck cancer. An experienced practitioner may manage this pain by understanding the multifactorial mechanisms of pain and the various pharmacotherapies available. Pain should be managed with multiple medications in a multimodal approach, and nonpharmacologic therapies should be considered as well.

Efficacy of a new once daily hydromorphone formulation in comparison with twice daily administration in chronic pain: a randomized, double-blind, cross-over study

Objective Efficacy and safety of a novel multiple-unit hydromorphone once daily (HOD) was compared to an established hydromorphone twice daily (HTD) regimen in patients with moderate-to-severe chronic pain. Design and methods The results from a randomized, double-blind, multicenter, cross-over trial in patients (n = 37) with chronic malignant or non-malignant pain are reported. The primary efficacy parameter was current pain on 0-100 mm VAS assessed four times daily and prior to intake of rescue medication (immediate-release hydromorphone) throughout the last 5 days with each treatment (after an 8 day build-up period to avoid carry-over effects). Total daily dose of hydromorphone (TDD: 8-32 mg/day) was kept stable during the double-blind treatment phase. Results The difference observed in mean current pain (-0.92 mm VAS) over the 5 day assessment period between HOD and HTD (28.44 mm vs. 29.36 mm VAS) was found to lack clinical relevance, as the 95% CI (-4.10 to 2.28 mm VAS) did not exceed the prespecified limit for non-inferiority of 9 mm VAS. Results from the full analysis set were consistent with per protocol data confirming robustness, as did the data for 12 h recalled pain assessed at 08:00 h and 20:00 h, showing no significant differences between once and twice daily medication. Both treatments produced effective and stable pain control with only minor day-to-day and intra-day fluctuations. Switching between treatments was suitable, considering both efficacy and safety, as no relevant or significant differences in adverse events were seen (25.0% HOD, 24.3% HTD). Most frequently typical side-effects of opioid therapy were observed, such as nausea, vomiting and headache. Conclusion Although this study was of short duration and included a limited number of patients, the results confirm that the new HOD is as effective and safe as the established HTD.

Tramadol in traumatic brain injury: Should we continue to use it?

Background and Aims:

Tramadol is commonly used to treat moderate to moderately-severe pain in adults. We aimed to analyze the clinical relevance of tramadol use during weaning and extubation in patients with traumatic brain injury (TBI).

Material and Methods:

A retrospective observational study was conducted and included all the intubated TBI patients at the level I trauma center between 2011 and 2012. Data included patient's demographics, mechanism of injury (MOI), Glasgow Coma Scale (GCS), injury severity score, length of Intensive Care Unit (ICU) stay length of stay (LOS), agitation scale, analgesics, failure of extubation and tracheostomy. Patients were divided into two groups based on whether they received tramadol (Group 1) or not (Group 2) during ventilatory weaning. Chi-square and Student's t-tests were used for categorical and continuous variables; respectively. Logistic regression analysis was performed for predictors of agitation in ICU.

Results:

The study included 393 TBI patients; the majority (96%) was males with a mean age of 33.6 ± 14 years. The most common MOI were motor vehicle crash (39%), fall (29%) and pedestrian (17%). The associated injuries were mainly chest (35%) and abdominal (16%) trauma. Tramadol was administered in 51.4% of TBI patients. Tracheostomy was performed in 12.4% cases. Agitation was observed in 34.2% cases. Group 1 patients had significantly lower age (31.6 ± 12.4 vs. 35.7 ± 15.6; P = 0.005) and head AIS (3.5 ± 0.8 vs. 3.9 ± 0.9; P = 0.001) compared to Group 2. The incidence of agitation, ICU and hospital LOS were higher in Group 1. Failure of extubation and tracheostomy were reported more frequently in Group 1 (P = 0.001). On multivariate analysis, tramadol use was an independent predictor for agitation (adjusted odds ratio 21; P = 0.001), followed by low GCS.

Conclusion:

Patients with TBI who received tramadol are more likely to develop agitation, undergo tracheostomy and to have longer hospital LOS. Therefore, an extensive risk-benefit assessment would help to attain maximum efficacy of the drug in TBI patients.

Morphine-sparing effect by COX-1 inhibitor sustains analgesic function without compromising antigen-specific immunity and antitumor effect of naked DNA vaccine

Morphine and ketorolac, two analgesics with different mechanisms, have been widely used in controlling cancer pain and postoperative pain in surgery. Our previous study revealed that morphine could suppress the anti-tumor effect of antigen-specific DNA vaccine. In this study, we further evaluated and compared another analgesic drug, ketorolac, with morphine for its analgesic functions and the antitumor immunities of antigen-specific DNA vaccine. We first observed that ketorolac-treated mice did not enhance tumorigenesis nor suppress the anti-tumor effects of antigen-specific (calreticulin linked to HPV16 E7) CRT/E7 DNA vaccine. We then demonstrated that ketorolac was less potent in inducing apoptosis of T lymphocytes and the generation of reactive oxygen species, in reducing mitochondrial membrane potentials, and leading to the activation of caspases 3 and 7 in T lymphocytes than morphine. When CRT/E7 DNA vaccinated mice treated with ketorolac, the declines of frequencies of E7-specific IFN-gamma-secreting CD8+ T cell precursors were slower in the morphine-treated group. CRT/E7 DNA vaccinated mice, treated with a mixture of morphine and ketorolac, could maintain the analgesic function without experiencing a decrease in the anti-tumor effects. CRT/E7 DNA vaccine with the opioid-sparing effect of ketorolac could provide potent anti-tumor effects and good analgesic function.

A guide to cancer pain management

Most, if not all, cancer patients require care from community teams at some stage during their disease trajectory. For many of these patients, community nurses and General Practitioners are the main point of contact. Pain is reported by between 55-95% of patients with advanced or terminal disease. Optimal pain control positively impacts on the physical, emotional and functional well-being of the patient. Despite the existence of guidelines (WHO, 1996) (SIGN, 2000) and a wealth of literature on cancer pain management, half of all patients in Western countries still do not receive adequate pain relief. This article looks at the reasons behind this and provides community nurses with an overview of up-to-date information on pain pathophysiology and management, so that the control of cancer pain can be optimized in the community.

[Outpatient opiate therapy in cancer patients during their last days of life]

BACKGROUND

Pain is one of the symptoms that many tumor patients are especially afraid of in the final phase of their illness. Symptoms can change rapidly, making quick adaptation of the therapy necessary. This poses particular challenges to organizational structures in outpatient treatment if the patients' desire to spend their last days of life in their accustomed surroundings is to be realized.

METHODS

Pain intensity and the associated symptoms in a WHO step III opiate therapy during the last 3 days of life were investigated retrospectively among 601 tumor patients who had received medical care from Home Care Berlin. Differences in gender, age, living conditions/care situation and place of death were evaluated with due consideration for the different pain medications administered and for the different forms and routes of administration.

RESULTS

More than 80% of the patients reported freedom from pain or only moderate pain during the opiate therapy. Care provided by the hospice-at-home medical service Home Care Berlin allowed excellent control of tumor patients' symptoms with only moderate side-effects in their final days of life. Among patients receiving opioids by the transdermal route there were significantly more frequent complaints of pain (p=0.004) and nausea (p=0.001). During the last days of life continuous subcutaneous infusions containing opiates facilitated good analgesia within an acceptable spectrum of side-effects. Most problems with controlling symptoms in outpatients were encountered in younger patients.

CONCLUSION

Morphine emerged as the drug of first choice in this investigation, because it can be given parenterally and also because of its price. The use of subcutaneous and intravenous administration systems such as PCA pumps requires trained nursing services and regular house visits by physicians experienced in palliative medicine.

A comparison of the resources used in advanced cancer care between two different strong opioids: an analysis of naturalistic practice in the UK

OBJECTIVE

To assess the resource implications of using strong opioids in patients with advanced cancer in the UK, based on naturalistic practice, in order to develop the evidence base supporting better management.

DESIGN AND SETTING

A modelling study performed from the perspective of the UK's National Health Service (NHS). Study participants and interventions: A data set was created from the DIN-link database comprising 986 patients with advanced cancer who were prescribed either 12-hourly sustained release morphine (SR morphine; MST Continuous) ( n = 784) or transdermal fentanyl (Durogesic) (n = 202) as their first strong opioid between 1st January 1998 and 30th September 2000 and died during that period.

METHODS

Palliative care-related resource use data were obtained from the DIN-link database. Unit costs at 2000/2001 prices were applied to the resource use values to determine the mean NHS cost of palliative care from the start of treatment until death.

RESULTS

Patients initially treated with transdermal fentanyl started their strong opioid regime 8.5 years after diagnosis compared to 6.4 years after diagnosis in those who started SR morphine. This equates to an overall survival period from diagnosis of 8.8 years and 7.4 years respectively. Nevertheless, the total NHS cost of palliative care was similar between treatment groups, ranging from a mean 3087-3462 pounds per patient. Hospitalisation accounted for up to 71% of the total cost and opioids accounted for up to a further 17%. Less than one-third of patients received 4-hourly morphine as part of their initial opioid treatment despite UK guidelines recommending that moderate-to-severe pain should always be managed initially with an immediate-release preparation. Additionally, patients who received transdermal fentanyl as part of their initial treatment received significantly more laxative prescriptions than patients who started with SR morphine.

CONCLUSIONS

SR morphine and transdermal fentanyl seem to be used in different situations. The results also confirm previous findings that pain management in cancer patients is often sub-optimal. The low contribution of opioids to the overall costs indicates that this should not be an obstacle to starting this aspect of palliative care earlier in disease progression. This characterisation of the resource implications of using SR morphine and transdermal fentanyl should enable purchasers and providers to optimise the availability of strong opioids for cancer patients on medical, economic and humanitarian grounds.

Opioid switch in palliative care, opioid choice by clinical need and opioid availability

Availability of different WHO-step 3 opioids has encouraged the discussion on their value and led to the concepts of opioid rotation. Rotation is suggested, when other measures fail to achieve optimal analgesia and tolerability in cancer pain treatment. Opioid use was assessed in a prospective cohort study of 412 palliative care patients from 14 inpatient and outpatient palliative care facilities in Germany. The most frequently used opioids at baseline were morphine and fentanyl. The most frequent changes in medication (N=106) occurred from oral to parenteral morphine. Only in 49 cases true switches to other long acting opioids were recorded. This is far less than expected from other reports. True switches and adverse side effects were found to occur more frequently in inpatients, while efficacy problems were more frequently recorded in outpatients. There was no correlation between the opioid used at baseline and switch frequency, but numbers of cases receiving other opioids than fentanyl or morphine were low. Reasons for and frequencies of changes in medication were found to be largely shaped by the setting reflecting patients' needs and clinical necessities. Recommendation of first line therapy and availability of opioid formulations define the frequency of opioid use. This impedes evaluation of specific differences between the opioids.

Beta-phenylethylamines and the isoquinoline alkaloids

This review covers beta-phenylethylamines and isoquinoline alkaloids and compounds derived from them, including further products of oxidation, condensation with formaldehyde and rearrangement, some of which do not contain an isoquinoline system, together with naphthylisoquinoline alkaloids, which have a different biogenetic origin. The occurrence of the alkaloids, with the structures of new bases, together with their reactions, syntheses and biological activities are reported. The literature from July 2001 to June 2002 is reviewed, with 581 references cited.

Relative efficacy of some prokinetic drugs in morphine-induced gastrointestinal transit delay in mice

AIM: To study the relative efficacy of cisapride, metoclopramide, domperidone, erythromycin and mosapride on gastric emptying (GE) and small intestinal transit (SIT) in morphine treated mice.

METHODS: Phenol red marker meal was employed to estimate GE and SIT in Swiss albino mice of either sex. The groups included were control, morphine 1 mg/kg (s.c. 15 min before test meal) alone or with (45 min before test meal p.o.) cisapride 10 mg/kg, metoclopramide 20 mg/kg, domperidone 20 mg/kg, erythromycin 6 mg/kg and mosapride 20 mg/kg.

RESULTS: Cisapride, metoclopramide and mosapride were effective in enhancing gastric emptying significantly (P < 0.001) whereas other prokinetic agents failed to do so in normal mice. Metoclopramide completely reversed morphine induced delay in gastric emptying followed by mosapride. Metoclopramide alone was effective when given to normal mice in increasing the SIT. Cisapride, though it did not show any significant effect on SIT in normal mice, was able to reverse morphine induced delay in SIT significantly (P < 0.001) followed by metoclopramide and mosapride.

CONCLUSION: Metoclopramide and cisapride are most effective in reversing morphine-induced delay in gastric emptying and small intestinal transit in mice respectively.

Pharmacotherapy of cancer-related episodic pain

Episodic pain is a transient increase in pain intensity over background pain. Episodic pain occurs commonly in cancer patients; it is a heterogeneous phenomenon that is incapacitating, debilitating and can have a significant impact on quality of life. Episodic pain can be difficult to manage; it is often unpredictable, typically of fast onset, of short duration and feels similar to background pain except that it may be more severe. The successful management of episodic pain can only be achieved following a thorough assessment. The subsequent management usually involves both pharmacological and non-pharmacological strategies integrated into the overall care and appropriate for the stage of the patient's disease. Pharmacological management includes the implementation of primary therapies (e.g., chemotherapy for the underlying aetiology of the pain, optimising the scheduled medication (e.g., analgesics and adjuvant analgesics) and specific pharmacological interventions for the episodic pain (e.g., rescue medication).