Inhaled fentanyl as a method of analgesia

Nebulized fentanyl does not improve exercise capacity or dyspnoea in fibrosing interstitial lung disease

Exercise intolerance and exertional dyspnoea are hallmarks of fibrosing interstitial lung disease (FILD) and are associated with worse prognosis and quality of life. Activation of pulmonary vagal afferents influences the ventilatory pattern and contributes to the sensation of dyspnoea. We tested the hypothesis that nebulized fentanyl, which might attenuate aberrant pulmonary afferent activity in FILD, reduces ventilation and dyspnoea while extending exercise endurance time (EET). In this randomized, single-blind, placebo-controlled study, eight FILD patients (two males, 71 ± 6 years of age) performed incremental cardiopulmonary cycle exercise tests following nebulization of either fentanyl citrate (100 µg) or 0.9% saline. Previous work indicated that this dose was unlikely to produce central effects. Comparisons between treatment conditions at rest were undertaken using Student's paired t-test, and exercise data were evaluated with two-way ANOVA with repeated measures. Dyspnoea was assessed using the Borg dyspnoea scale. Resting respiratory variables were not different following treatment with fentanyl and saline; however, resting heart rate was lower following fentanyl (P = 0.002) and remained lower throughout exercise compared with placebo (P = 0.008). Fentanyl did not increase EET (placebo 334 ± 117 s vs. fentanyl 348 ± 126 s, P = 0.250) although overall minute ventilation was reduced slightly (mean difference: -0.97 L/min, P = 0.022). There were no differences in ratings of dyspnoea intensity or unpleasantness between the conditions either at rest or at end-exercise. Nebulized fentanyl did not improve EET or exercise dyspnoea but did decrease minute ventilation during exercise, although the extent of this reduction appears clinically insignificant. These findings suggest that nebulized fentanyl is unlikely to offer significant benefits for enhancing exercise capacity in FILD.

Effect of different doses of dexmedetomidine as an adjuvant to lignocaine nebulization: A comparative study during awake flexible fiberoptic bronchoscopy

Background and Aims

Mild to moderate sedation during bronchoscopy is essential for patient safety, comfort during and after the procedure, and to facilitate the performance of the bronchoscopist. Dexmedetomidine is a highly selective, centrally acting α-2 agonist used to provide conscious sedation during various procedures. The aim of this study was to compare the efficacy of three different doses of dexmedetomidine nebulization as an adjuvant to lignocaine during bronchoscopy.

Material and Methods

Ninety American Society of Anesthesiologists physical status I/II patients, aged from 18 to 60 years, scheduled for an elective bronchoscopy, were recruited. They were divided into three groups: 30 patients in each group. Group I: The patient was nebulized with a mixture of 4 ml of 4% lignocaine and dexmedetomidine 0.5 μg/kg. Group II: The patient was nebulized with a mixture of 4% lignocaine, 4 ml, and dexmedetomidine, 1 μg/kg. Group III: The patient was nebulized with 4% lignocaine 4 ml and dexmedetomidine 1.5 μg/kg.

Results

The mean cough score was (1.17 ± 0.37), (1.40 ± 0.49), and (1.70 ± 0.75) in group III, group II, and group I, respectively. A significant difference was found between the groups. Patients were more comfortable with a statistically significant difference in the comfort score in group III as compared to group II and group I.

Conclusion

Dexmedetomidine nebulization in a dose of 1.5 μg/kg (compared to 1 μg/kg or 0.5 μg/kg) as an adjuvant to lignocaine, provides better bronchoscopy conditions and patient satisfaction.

Drugs as Chemical Weapons: Past and Perspectives

The emergence of modern chemical weapons and chemical warfare is traditionally associated with World War I, but the use of poisons in the military has its roots deep in the past. The sources of these poisons have always been natural agents that also served as medicines. This relationship between poison and medicine, and nowadays between chemical warfare and medicine, or between 'military chemistry' and pharmacy, appears to be very important for understanding not only the history but also the possible future of both phenomena. This article looks at some historical examples of the use of drugs as chemical weapons and, conversely, the use of chemical weapons as medicines. It seeks to find answers to some questions that are particularly relevant to the implementation of the Chemical Weapons Convention, which aims to achieve a world without chemical warfare.

Inhaled opioids for cancer pain relief: A narrative review

Despite the many new possibilities, cancer pain treatment is not always effective and often poses a challenge for practitioners. At the end-of-life care, both oral and subcutaneous drug delivery very often are not attainable. The increasing number of patients in terminal stage of chronic diseases forced us to look for the alternative ways of administration of pain treatment. In this context, the potentially rapid onset of action and ease of use make aerosolized drug delivery an attractive option in palliative care settings. The objective of this review was to identify literature on pain relief with inhaled opioids. The evidence suggests that nebulized opioids might be effective in the treatment of pain in various aetiologies; however, randomized controlled studies on nebulization therapy for cancer pain are lacking.

Recent advances in drug delivery to the central nervous system by inhalation

INTRODUCTION

Drugs need to enter the systemic circulation efficiently before they can cross the blood-brain barrier and reach the central nervous system. Although the respiratory tract is not a common route of administration for delivering drugs to the central nervous system, it has attracted increasing interest in recent years for this purpose.

AREAS COVERED

In this article, we compare pulmonary delivery to three other common routes (parenteral, oral, and intranasal) for delivering drugs to the central nervous system, followed by summarising the devices used to aerosolise neurological drugs. Recent studies delivering drugs for different neurological disorders via inhalation are then discussed to illustrate the strengths of pulmonary delivery.

EXPERT OPINION

Recent studies provide strong evidence and rationale to support inhaling neurological drugs. Since inhalation can achieve improved pharmacokinetics and rapid onset of action for multiple drugs, it is a non-invasive and efficient method to deliver drugs to the central nervous system. Future research should focus on delivering other small and macro-molecules via the lungs for different neurological conditions.

The use of heat to deliver fentanyl via pulmonary drug delivery

The golden standard to treat acute pain is by intravenous drug delivery of opioids such as fentanyl or morphine. Intravenous drug delivery requires the placement of an intravenous (IV) port, which can cause infections, dislodgments, and distress to the patients, and therefore a non-invasive method is desirable. Pulmonary drug delivery is a non-invasive method that has been shown to be a good alternative to intravenous administration. New devices have been investigated for treating acute pain by delivering fentanyl by heat. The pure drug, fentanyl, is applied onto a surface which is then heated up to 350 °C and inhaled, resulting in no formation of degradation products. Furthermore, forced degradation of fentanyl has been studied which showed that longer heating time and higher temperatures will result in the formation of degradation products. The evidence indicates that heat can be used to deliver drugs to the lungs where fast onset reaction can be obtained giving fast and non-invasive pain relief.

Inspiratory neural drive and dyspnea in interstitial lung disease: Effect of inhaled fentanyl

BACKGROUND

Exertional dyspnea in interstitial lung disease (ILD) remains difficult to manage despite advances in disease-targeted therapies. Pulmonary opioid receptors present a potential therapeutic target for nebulized fentanyl to provide dyspnea relief.

METHODS

ILD patients were characterized with reference to healthy volunteers. A randomized, double-blind, placebo-controlled crossover comparison of 100 mcg nebulized fentanyl vs placebo on dyspnea intensity and inspiratory neural drive (IND) during constant work rate (CWR) cycle exercise was performed in 21 ILD patients.

RESULTS

Dyspnea intensity in ILD increased in association with an increase in IND (diaphragm activation) from a high resting value of 16.66 ± 6.52 %-60.04 ± 12.52 % of maximum (r = 0.798, p < 0.001). At isotime during CWR exercise, Borg dyspnea intensity ratings with fentanyl vs placebo were 4.1 ± 1.2 vs 3.8 ± 1.2, respectively (p = 0.174), and IND responses were also similar.

CONCLUSION

IND rose sharply during constant work rate exercise in association with dyspnea intensity in mild to moderate ILD but was not different after nebulized fentanyl compared with placebo.

Nebulized Fentanyl for Dyspnea: A Retrospective Chart Review

Nebulized fentanyl is well established for analgesia but its use for dyspnea requires further investigation. The aim of our study was to determine the effectiveness of nebulized fentanyl in treating patients with dyspnea and to determine if there were harmful side effects described by patients or their providers. We used a convenience sample of patients from July 1 2014 to July 1 2018 and performed a retrospective chart review. We found that 360 doses of nebulized fentanyl were given to 73 patients during that time period. Of the 73 patients evaluated, 32 patients (43.8%) were female and forty-one were male (56.1%). The median age was 67 and the median length of stay was 9 days. There were no documented findings of bronchospasm, hypotension, or allergic reaction in any of the medical records reviewed. Patients treated with nebulized fentanyl for dyspnea showed a mean decreased respiratory rate of 4.3 breaths/min and a mean increased oxygen saturation of 2.3%. Also, 71% of patients with documented responses experienced an improvement in their dyspnea. Our preliminary data suggest that nebulized fentanyl has limited side effects and may have a role in the treatment of dyspnea. Further research is necessary to determine its efficacy.

Novel Approaches for Treating Pain in Children

PURPOSE OF REVIEW

Good pain management in children, especially those at end of life, is a crucial component of palliative medicine. The current review assesses some of the new and/or innovative ways to manage pain in children. The article focuses on some recent medications/pharmaceutical options such as cannabinoids and also innovative ways to administer medication to children, such as intranasal and inhalation.

RECENT FINDINGS

Current approaches to pain management now include (1) new uses of old drugs such as ketamine and lidocaine, (2) use of new drugs/medications such as cannabinoids, and (3) creative use of old technology such as atomizers, intranasal drops, and inhalation. Typically, novel approaches to care rarely start in pediatrics or palliative care. The current review has presented some new and old drugs being utilized in new and old ways.

A retrospective analysis of nebulized versus intravenous fentanyl for renal colic

STUDY OBJECTIVE

To assess the effectiveness of nebulized fentanyl used for analgesia in renal colic.

MATERIALS/METHODS

This research was planned as a randomized, blinded study in which prospectively collected data were analyzed retrospectively to compare nebulized and intravenous (iv) fentanyl therapies. Patients with renal colic with 'moderate' or worse pain on a four-point verbal pain score (VPS) or with pain of 20mm or above on a 100-mm visual analogue score (VAS) at time of presentation were randomized into iv fentanyl (n=62) or nebulized fentanyl (n=53) study groups. Decreases in VAS and VPS scores at 15 and 30min compared to baseline, rescue analgesia requirements and side-effects between the groups were compared.

RESULTS

Both iv fentanyl and nebulized fentanyl provided effective analgesia in renal colic patients at the end of 30min. However, iv fentanyl provided more rapid and more effective analgesia than nebulized fentanyl. Patients receiving iv fentanyl had lower rescue analgesia requirements than those receiving nebulized fentanyl (37.1% vs 54.7%), although the difference was not statistically significant (p=0.058). In addition, side-effects were more common in the iv fentanyl group compared to the nebulized fentanyl group (22.1% vs 9.4%), although the difference was also not significant (p=0.058).

CONCLUSION

Nebulized fentanyl provides effective analgesia in patients with renal colic. However, iv fentanyl exhibits more rapid and more powerful analgesic effects than nebulized fentanyl. Nonetheless, due to its ease of use and few potential risks and side-effects the nebulized form can be used as an alternative in renal colic.

Nebulized Fentanyl in Acute Pain: A Systematic Review

OBJECTIVE

To provide a systematic review of the current role of nebulized fentanyl in acute pain and potentially other conditions.

DATA SOURCES

A MEDLINE literature search inclusive of the dates 1946 to May 2016 was performed using the following search terms: fentanyl and administration, inhaled Excerpta Medica was searched from 1980 to May 2016 using the following search terms: exp fentanyl/inhalation drug administration Additionally, Web of Science was searched using the terms fentanyl and pain inclusive of 1945 to May 2016.

STUDY SELECTION AND DATA EXTRACTION

We utilized the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines to select English language, human primary literature, review articles, and supporting data assessing the efficacy of nebulized fentanyl in acute pain.

DATA SYNTHESIS

Seven clinical trials have demonstrated no difference in efficacy between nebulized fentanyl and intravenous (IV) opioids. Few adverse effects were reported; however, the trials were of short duration. Nebulized fentanyl appeared to be a rapid-acting analgesic that does not require IV access.

CONCLUSION

Evidence suggests that nebulized fentanyl is as effective as IV opioids in the treatment of acute pain, with relatively few adverse effects. However, questions remain about the extemporaneous preparation of fentanyl nebulized solution, the variability in nebulization devices, and ensuring consistent drug delivery to distal airways in the clinical setting. The abuse potential of nebulized fentanyl should also be considered.

Devices for dry powder drug delivery to the lung

Dry powder inhalers (DPIs) are an important and increasingly investigated method of modern therapy for a growing number of respiratory diseases. DPIs are a promising option for certain patient populations, and may help to overcome several limitations that are associated with other types of inhalation delivery systems (e.g., accuracy and reproducibility of the dose delivered, compliance and adherence issues, or environmental aspects). Today, more than 20 different dry powder inhalers are on the market to deliver active pharmaceutical ingredients (APIs) for local and/or systemic therapy. Depending on the mechanism of deagglomeration, aerosolization, dose metering accuracy, and the interpatient variability, dry powder inhalers demonstrate varying performance levels. During development, manufacturers focus on improving aspects characteristic of their specific DPI devices, depending on the intended type of application and any particular requirements associated with it. With the wide variety of applications related to specific APIs, there exists a range of different devices with distinct features. In addition to the routinely used multi-use DPIs, several single-use disposable devices are under development or already approved. The recent introduction of disposable devices will expand the range of possible applications for use by including agents such as vaccines, analgesics, or even rescue medications. This review article discusses the performance and advantages of recently approved dry powder inhalers as well as disposable single-use inhalers that are currently under development.

Does nebulized fentanyl relieve dyspnea during exercise in healthy man?

Few therapies exist for the relief of dyspnea in restrictive lung disorders. Accumulating evidence suggests that nebulized opioids selective for the mu-receptor subtype may relieve dyspnea by modulating intrapulmonary opioid receptor activity. Our respective primary and secondary objectives were to test the hypothesis that nebulized fentanyl (a mu-opioid receptor agonist) relieves dyspnea during exercise in the presence of abnormal restrictive ventilatory constraints and to identify the physiological mechanisms of this improvement. In a randomized, double-blind, placebo-controlled crossover study, we examined the effect of 250 μg nebulized fentanyl, chest wall strapping (CWS), and their interaction on detailed physiological and perceptual responses to constant work rate cycle exercise (85% of maximum incremental work rate) in 14 healthy, fit young men. By design, CWS decreased vital capacity by ∼20% and mimicked the negative consequences of a mild restrictive lung disorder on exercise endurance time and on dyspnea, breathing pattern, dynamic operating lung volumes, and diaphragmatic electromyographic and respiratory muscle function during exercise. Compared with placebo under both unrestricted control and CWS conditions, nebulized fentanyl had no effect on exercise endurance time, integrated physiological response to exercise, sensory intensity, unpleasantness ratings of exertional dyspnea. Our results do not support a role for intrapulmonary opioids in the neuromodulation of exertional dyspnea in health nor do they provide a physiological rationale for the use of nebulized fentanyl in the management of dyspnea due to mild restrictive lung disorders, specifically those arising from abnormalities of the chest wall and not affiliated with airway inflammation.

Nebulized fentanyl vs intravenous morphine for ED patients with acute limb pain: a randomized clinical trial

OBJECTIVE

Intravenous morphine has been used as a common method of pain control in emergency care. Nebulized fentanyl is also an effective temporary substitute. This study was designed to compare the effectiveness of nebulized fentanyl with intravenous (IV) morphine on management of acute limb pain.

METHODS

This was a placebo-controlled, double-blind randomized clinical trial. Ninety emergency department patients with moderate to severe pain aged 15 to 50 years were blocked randomized and enrolled in this study. Forty-seven patients in the experimental group received nebulized fentanyl (4 μg/kg) and IV normal saline as placebo, and the remaining 43 patients in the control group received IV morphine (0.1 mg/kg) and nebulized normal saline as placebo. All participants' pain scores were assessed by Numerical Rating Scale before and after intervention at 5-, 10-, 15-, 30-, 45-, and 60-minute intervals. Patients' vital sign and possible adverse effects were recorded respectively. Finally, all participants were assessed for their satisfaction.

RESULTS

The mean initial pain score in the experimental group was 8.7 and 8.4 in the control group (P = .1). Pain relief in both groups after 5 and 10 minutes were similar (P = .72). Although the pain relief was significantly greater with fentanyl at 15 minutes, this difference is not clinically significant. Pain management in both groups was successful and was more than 3 scores reduction in Numerical Rating Scale. Patient satisfaction in both groups was similar. No adverse effects were reported in the experimental group.

CONCLUSION

This study suggests that nebulized fentanyl is a rapid, safe, and effective method for temporary control of acute limb pain in emergency department patients.

Nebulised fentanyl for post-operative pain relief, a prospective double-blind controlled randomised clinical trial

Background and Aim:

Intravenous (IV) route for fentanyl administration is the gold standard for post-operative pain relief, but complications such as respiratory depression, bradycardia and hypotension have limited this route. The aim of this randomised controlled trial was to compare the efficacy of nebulised fentanyl with IV fentanyl for post-operative pain relief after lower abdominal surgery.

Methods:

In the post-operative care unit, at the time of first onset of pain (visual analogue scale- VAS score > 4) patients were randomised into three groups and fentanyl was administered either IV 2 μg/kg or by nebulisation of solution containing 3 or 4 μg/kg fentanyl over 8 min in 90 patients divided into three groups of 30 each. Observation were made for pain relief by visual analogue scale score 0-10. Adverse effects such as respiratory depression, bradycardia and hypotension were also recoded. Statistical analysis was performed using Medcalc software version 12, 2012. (MedCalc Software, Ostend, Belgium).

Results:

In the nebulisation group, it was observed that the analgesic efficacy of fentanyl was dose dependent with a delayed onset of analgesia (10 min vs. 5 min). Nebulisation with 4 μg/kg fentanyl produced analgesia at par to 2 μg/kg IV fentanyl with prolonged duration (90 min vs. 30 min) and with significantly less adverse effects.

Conclusions:

This study shows that nebulisation with 4 μg/kg fentanyl may be used as an alternative to IV 2 μg/kg fentanyl for adequate post-operative pain relief.

Inhaled fentanyl aerosol in healthy volunteers: pharmacokinetics and pharmacodynamics

BACKGROUND

Rapid delivery of potent opioid to the systemic circulation is an important feature for the effective treatment of acute and acute-on-chronic breakthrough pain. The delivery of different opioids by the pulmonary route has been inconsistent, usually resulting in low bioavailability of the drug. Staccato® Fentanyl for Inhalation is a handheld inhaler producing a single metered dose of aerosolized fentanyl during a single inspiration. The aerosol is of high purity (≥98%) at a particle size (1 to 3.5 microns) shown to be best for pulmonary absorption.

METHODS

We conducted the study in healthy volunteers in 2 stages. In the crossover stage, 10 subjects received IV fentanyl 25 µg and inhaled fentanyl 25 µg on separate occasions. The dose escalation stage was a multidose, randomized, double-blind, placebo-controlled, single-period dose escalation study of inhaled fentanyl (50 to 300 µg). Serial blood sampling was performed over an 8-hour period after drug administration to determine the pharmacokinetic profile, and serial pupillometry was performed as a measure of pharmacodynamic effect.

RESULTS

In the crossover stage the pharmacokinetic profiles of the inhaled and IV fentanyl showed similar peak arterial concentrations and areas under the curve. The time to maximum concentration was slightly shorter for the inhaled than IV fentanyl, 20.5 and 31.5 seconds, respectively. In the dose escalation stage the administration of repeated doses resulted in predictable, dose-dependent serum concentrations.

CONCLUSIONS

This study has demonstrated that the pharmacokinetic profile of single doses of inhaled fentanyl is comparable to IV administration.

Inhaled fentanyl citrate improves exercise endurance during high-intensity constant work rate cycle exercise in chronic obstructive pulmonary disease

CONTEXT

Activity limitation and dyspnea are the dominant symptoms of chronic obstructive pulmonary disease (COPD). Traditionally, efforts to alleviate these symptoms have focused on improving ventilatory mechanics, reducing ventilatory demand, or both of these in combination. Nevertheless, many patients with COPD remain incapacitated by dyspnea and exercise intolerance despite optimal therapy.

OBJECTIVES

To determine the effect of single-dose inhalation of nebulized fentanyl citrate (a μ-opioid agonist drug) on exercise tolerance and dyspnea in COPD.

METHODS

In a randomized, double-blind, placebo-controlled, crossover study, 12 stable patients with COPD (mean ± standard error of the mean post-β(2)-agonist forced expiratory volume in one second [FEV(1)] and FEV(1) to forced vital capacity ratio of 69% ± 4% predicted and 49% ± 3%, respectively) received either nebulized fentanyl citrate (50 mcg) or placebo on two separate days. After each treatment, patients performed pulmonary function tests and a symptom-limited constant work rate cycle exercise test at 75% of their maximum incremental work rate.

RESULTS

There were no significant postdose differences in spirometric parameters or plethysmographic lung volumes. Neither the intensity nor the unpleasantness of perceived dyspnea was, on average, significantly different at isotime (5.0 ± 0.6 minutes) or at peak exercise after treatment with fentanyl citrate vs. placebo. Compared with placebo, fentanyl citrate was associated with 1) increased exercise endurance time by 1.30 ± 0.43 minutes or 25% ± 8% (P=0.01); 2) small but consistent increases in dynamic inspiratory capacity by ∼0.10 L at isotime and at peak exercise (both P≤0.03); and 3) no concomitant change in ventilatory demand, breathing pattern, pulmonary gas exchange, and/or cardiometabolic function during exercise. The mean rate of increase in dyspnea intensity (1.2 ± 0.3 vs. 2.9 ± 0.8 Borg units/minute, P=0.03) and unpleasantness ratings (0.5 ± 0.2 vs. 2.9 ± 1.3 Borg units/minute, P=0.06) between isotime and peak exercise was less after treatment with fentanyl citrate vs. placebo.

CONCLUSION

Single-dose inhalation of fentanyl citrate was associated with significant and potentially clinically important improvements in exercise tolerance in COPD. These improvements were accompanied by a delay in the onset of intolerable dyspnea during exercise near the limits of tolerance.

Pulmonary delivery of therapeutic compounds for treating CNS disorders

Delivering therapeutic compounds via the lungs presents potential advantages relative to other routes of administration. Depending on the compound and the disease state, these advantages may include: non-invasive medication delivery, ease of administration, higher bioavailability leading to dose sparing and lower systemic toxicity, potentially greater blood–brain barrier penetration and rapid pharmacodynamic effect. The practice of inhaling drugs has been around for centuries, including both medical and recreational usage. It is only more recently that formal clinical development programs have been undertaken specifically to use medication delivery via the lung to achieve systemic blood levels for the treatment of CNS disorders. At present, there are several CNS therapies being developed for pulmonary administration, with some of those programs at or near the marketing authorization stage. While there are still regulatory hurdles before these therapies can be put into practice, the success of these programs thus far demonstrates the scientific viability of inhalation therapies for treating CNS disorders.

Formulations of fentanyl for the management of pain

Fentanyl is an opioid initially developed for parenteral administration. While oral administration is not an option due to a high first-pass metabolism, its high potency and lipophilicity have made a number of new routes of administration feasible. The transdermal therapeutic system offers an excellent option for long-term treatment of cancer and chronic pain, achieving stable plasma concentrations over the treatment period. The recent change from reservoir to matrix systems has made these systems more convenient to wear and safer to use, while being bioequivalent. In contrast, the patient-controlled iontophoretic transdermal system has been developed to enable on-demand delivery of transdermal bolus doses of fentanyl to treat postoperative pain. It offers a needle-free system to provide patient-controlled analgesia otherwise offered by intravenous pumps. However, due to technical difficulties the system is currently not clinically available. Oral transmucosal fentanyl utilizes the rapid uptake through the buccal mucosa to achieve high plasma concentrations rapidly and is indicated to treat breakthrough pain in patients who are not opioid-naive. The recently introduced fentanyl buccal tablets offer slightly better pharmacokinetics for the same indication. The intranasal route is another option to achieve rapid uptake of fentanyl, and is currently being investigated to provide acute and breakthrough pain relief. Transpulmonary administration of fentanyl remains experimental and this route of administration is not yet in clinical use. Overall, the specific pharmacological and physicochemical properties of fentanyl have made this compound highly suitable for novel routes of administration in a range of clinical indications.

Advanced formulation design: improving drug therapies for the management of severe and chronic pain

Chronic pain is a condition affecting a vast patient population and resulting in billions of dollars in associated health care costs annually. Sufferers from severe chronic pain often require [correction of requite] twenty-four hour drug treatment through intrusive means and/or repeated oral dosing. Although the oral route of administration is most preferred, conventional immediate release oral dosage forms lead to inconvenient and suboptimal drug therapies for the treatment of chronic pain. Effective drug therapies for the management of chronic pain therefore require advanced formulation design to optimize the delivery of potent analgesic agents. Ideally, these advanced delivery systems provide efficacious pain therapy with minimal side effects via a simple and convenient dosing regime. In this article, currently commercialized and developing drug products for pain management are reviewed with respect to dosage form design as well as clinical efficacy. The drug delivery systems reviewed herein represent advanced formulation designs that are substantially improving analgesic drug therapies.

Pulmonary delivery of opioids as pain therapeutics

Pulmonary opioid delivery, on the basis of the fact that small molecular entities can be rapidly and completely absorbed from the peripheral lung, poses a unique opportunity for the treatment of severe (breakthrough) pain, which currently is treated with intravenous therapy. Early clinical studies involving inhaled opioids were focused on treatment of dyspnoea and not pain management, but they showed that inhalation of various opioid compounds is safe, even in severely ill patients. The advent of specialized and efficient pulmonary drug delivery systems has facilitated the evaluation of inhaled opioids, such as morphine and fentanyl, for management of severe pain associated with surgery or malignant disease. This review will summarize recent literature on the pharmacokinetics and pharmacodynamics of inhaled opioids and will discuss safety and efficacy in comparison to injection and other opioid dosage forms available for pain therapy. Finally, regulatory considerations will be discussed towards the approval of this new delivery paradigm for opioid drugs.

Preliminary findings for preemptive analgesia with inhaled morphine: efficacy in septoplasty and septorhinoplasty cases

OBJECTIVE

The aim of this study was to assess the efficacy of inhaled morphine for preemptive analgesia in patients who undergo septoplasty or septorhinoplasty. STUDY PLAN AND METHODS: Eighty ASA I-II patients scheduled for septoplasty or septorhinoplasty were recruited and randomly divided into 2 groups that received different treatments 10 minutes prior to induction. The preemptive analgesia group (Group P, n = 40) received 65 mug kg(-1) morphine sulphate (a 3-mL volume) via an oral nebulizer, and the control group (Group C, n = 40) received 3 mL 0.9% sodium chloride (physiological saline) via the same type of nebulizer. Blood pressure, oxygen saturation, heart rate, time to first requirement for analgesia, and occurrence of nausea/vomiting were recorded.

RESULTS

There were no significant differences between Groups P and C with respect to age, body weight, sex distribution, or duration of surgery. There was also no significant difference between the group frequencies of postoperative nausea/vomiting. The time to first requirement for analgesia was significantly longer in Group P than Group C.

CONCLUSION

The results of this preliminary study suggest that a single dose of inhaled morphine administered preemptively prior to septoplasty or septorhinoplasty provides effective postoperative analgesia.

EBM RATING

B-3b.

Inhaled methoxyflurane as a prehospital analgesic in children

OBJECTIVE

Despite widespread use of methoxyflurane as an inhaled analgesic by ambulance services in Australia there are no published data as to its use pattern, efficacy and safety in the prehospital setting. We set out to characterize methoxyflurane use in children in the prehospital setting.

METHODS

An observational case series was conducted over an 8 month period. Children who received methoxyflurane while being transported to a tertiary children's hospital by ambulance were enrolled. We analysed indications for use, verbal numerical pain scores, adverse events and depth of sedation based on paramedic, patient, parent and ED staff surveys and review of ambulance care records.

RESULTS

During the study period 105 patients were enrolled with an age range of 15 months to 17 years (median age 11 years). Methoxyflurane was mainly used for extremity injuries (82%). Paramedic pain scores dropped from a mean of 7.9 (95% confidence interval [CI] 7.5-8.3) prior to methoxyflurane use to 4.5 (95% CI 3.9-5.0) at 2-5 min and to 3.2 (95% CI 2.8-3.7) at 10 min. There were no serious adverse events (one-sided 97.5% CI 0-3%). Mild adverse events occurred in 38 patients (36.2%; 95% CI 27.0-46.1%). Five of 15 (33.3%) patients under 5 years of age were deeply sedated.

CONCLUSION

In the present paediatric case series methoxyflurane appears to be an efficacious analgesic with a low adverse events profile. In young children in particular it can briefly lead to deep sedation.

Endomorphin1 and endomorphin2, endogenous potent inhibitors of electrical field stimulation (EFS)-induced cholinergic contractions of rat isolated bronchus

In the present study, we determined whether endomorphin1 (EM1) and endomorphin2 (EM2), selective endogenous mu-opioid receptor (MOR) agonists, inhibited the response to EFS in rat isolated bronchus in a concentration- and frequency-dependent manner. EM1 (1 microM) produced significant inhibition at relatively low frequencies (< 5 Hz) (74.02 +/- 5.53%, 56.16 +/- 10.24% and 37.64 +/- 5.92% inhibition at 1, 2 and 4 Hz, respectively, p < 0.05 versus control), but no significant inhibition at 8, 16, 32 and 64 Hz (17.15 +/- 9.4%, 14.51 +/- 4.23%, 9.11 +/- 2.38% and 5.93 +/- 3.5%, respectively, p > 0.05 versus control). Similar modulations were observed in response to EM2 (1 microM). It is therefore considered that the inhibition effects of EM1 and EM2 may take place at frequencies under physiological conditions. Furthermore, EM1 and EM2 (0.01-10 microM) induced inhibition of cholinergic constriction in a dose-dependent manner at 1, 2 and 4 Hz. The inhibitory effect on EFS was blocked by the opioid receptor antagonist naloxone (10 microM), indicating that opioid receptors were involved. Neither EM1 nor EM2 (1 microM) had an effect on the contractile response to exogenous acetylcholine, indicating a prejunctional effect. All the results indicate that EM1 and EM2 are potent inhibitors of EFS-induced cholinergic bronchoconstriction. These also imply that EM1 and EM2 may modulate cholinergic bronchoconstriction under physiological conditions and that these tetrapeptides could have therapeutic potential in the treatment of airway diseases.

Paediatric prehospital analgesia in Auckland

OBJECTIVES

The objectives of the present study were: To determine whether the age of a child influences the likelihood of their receiving prehospital analgesia from the Auckland ambulance service. To investigate the effect of age on ambulance officers' decision-making and use of analgesia.

METHODS

A prospective study of children arriving by ambulance at Starship Children's Emergency Department Auckland, with a diagnosis of limb fracture or burn, was undertaken over 2 months in 2002. A concurrent questionnaire survey investigated ambulance officers' use of analgesia in children.

RESULTS

No child aged less than 5 years (n = 10) compared with 51% between 5 and 15 years of age (n = 35) received prehospital analgesia (P = 0.003). On arrival in hospital 70% aged less than 5 years compared with 54% older than 5 years required i.v. opiate analgesia. Ambulance officers did not perceive that a child's age would significantly alter their decision to use analgesia.

CONCLUSIONS

In children, younger age is a significant risk factor for receiving inadequate prehospital analgesia. Ambulance officers' concern about the pain of injection is the major identified factor for the relative underuse of morphine observed in younger children.

A Prospective Randomized Trial of Nebulized Morphine Compared with Patient-Controlled Analgesia Morphine in the Management of Acute Thoracic Pain

BACKGROUND

Successfully managing pain for the trauma patient decreases morbidity, improves patient satisfaction, and is an essential component of critical care. Using patient-controlled analgesia (PCA) morphine to control pain may be complicated by concerns of respiratory depression, hemodynamic instability, addiction, urinary retention, and drug-induced ileus. Morphine is rapidly absorbed by mucosal surfaces in the respiratory tract, achieving systemic concentrations equal to 20% of equivalent intravenous doses. The purpose of this study was to evaluate the safety, efficacy, and utility of nebulized morphine in patients with posttraumatic thoracic pain.

METHODS

This double-blinded, prospective study randomized patients with severe posttraumatic thoracic pain into two groups. The experimental group (NMS) received nebulized morphine every 4 hours and normal saline by PCA. The control group (PCA) received nebulized saline every 4 hours and morphine by PCA. Dose adjustments were made based on patient response to treatments using a 10-point visual analog scale (VAS) for pain. Pulmonary function, pain relief (VAS), level of sedation (0-3), total drug administration, and systematic side effects were recorded.

RESULTS

Forty-four patients were randomized (22 per group). Seven hundred seventy observations were made. The mean 4-hour dose of morphine was 11.96 +/- 3.4 mg for NMS and 6.22 +/- 4.7 mg for PCA (p < 0.001). Patients with NMS had lower heart rates compared with PCA (79 +/- 11 bpm versus 92 +/- 12 bpm; p < 0.001) and were less sedated (0.33 +/- 0.7 versus 0.56 +/- 0.9; p = 0.03). The mean pain level (VAS) was 3.38 +/- 1.8 for NMS and 3.84 +/- 2.7 for PCA (p = 0.2). There was no difference between pain levels before and after dosing. There were no differences between groups with respect to arterial blood pressure, respiratory rate, vital capacity, mean forced expiratory volume in 1 second, spirometric volumes, or Sao2.

CONCLUSION

Nebulized morphine can be safely and effectively used to control posttraumatic thoracic pain. Pain can be successfully managed while vital capacity, mean forced expiratory volume in one second, and spirometric volumes are maintained. Compared with PCA morphine, nebulized morphine provides equivalent pain relief with less sedative effects.

Unexpected "gas" casualties in Moscow: a medical toxicology perspective

In October 2002, the Russian military used a mysterious "gas" to incapacitate Chechen rebels at a Moscow theater. Despite increased interest in the potential use of lethal chemical weapons in recent years, the medical community has paid little attention to the development of incapacitating, calmative, and "less than lethal" technologies. In this analysis, we review the events surrounding the use of a calmative "gas" during the Russian military action and discuss what is currently known about fentanyl derivatives, their aerosolization, and the rationale for their use as incapacitating agents. Collectively, the available evidence strongly suggests that a combination of a potent aerosolized fentanyl derivative, such as carfentanil, and an inhalational anesthetic, such as halothane, was used. The paper also assesses potential errors leading to the loss of a substantial number of hostages. Several lessons can be learned from this surprising and novel use of an incapacitating gas.

Options in prehospital analgesia

BACKGROUND

Prehospital analgesia options for paramedics have been limited due to the difficulty in achieving safe and effective pain relief without compromising transportation to hospital. The present paper identifies the analgesia methods currently available in the prehospital setting so as to evaluate the various options and highlight areas for future research.

METHODS

A literature review of Medline and Embase databases from 1966 until the present was undertaken. Further hand searching of all the references identified in these papers was also performed. All current literature was analysed and categorized according to one of four levels of evidence using National Health and Medical Research Council of Australia guidelines (1999).

RESULTS

There is a paucity of randomized control trials relating to prehospital analgesia. All published literature was level III or IV prospective or retrospective studies. Drug options used included nitrous oxide/oxygen mixtures, intravenous/intramuscular nalbuphine, intravenous tramadol and intravenous pure opiate agonists.

CONCLUSIONS

The evidence supporting analgesic options in the prehospital setting is limited. There are few published data in this area despite the inadequacy of pain relief being recognized as a weakness in prehospital care. Prehospital analgesia is an area worthy of innovative methods for the administration of safe and effective analgesics without significant impact on transport times. Such methods should be prospectively evaluated in well-constructed trials.

Sublingual fentanyl citrate for cancer-related breakthrough pain: a pilot study

The effects of sublingual fentanyl citrate (SLFC) were assessed in 11 hospice inpatients with cancer-related breakthrough pain. Patients were asked to rate their pain, using a visual analogue scale, before SLFC, then after 3, 5, 10, 15, 30, 45 and 60 min. Six patients (55%) had reductions in pain scores at 10 min and nine patients (82%) at 15 min. Ratings for SLFC were very good (18%), good (36%), moderate (28%), and bad (18%). Compared to the usual breakthrough medication, SLFC was better (46%), the same (36%), or worse (18%). Advantages of SLFC included ease of use, quick onset of action and no associated drowsiness. No systemic adverse events were noted, but two patients reported dry mouth and two a bitter taste. Two patients found it difficult to retain the medication under the tongue. Seven patients (64%) said they would continue to use SLFC. Sublingual fentanyl citrate appears safe and well tolerated by these patients. Randomized placebo-controlled and dose ranging studies are required to confirm these findings.

Pulmonary administration of aerosolised fentanyl: pharmacokinetic analysis of systemic delivery

AIMS

Pulmonary drug delivery is a promising noninvasive method of systemic administration. Our aim was to determine whether a novel breath-actuated, microprocessor-controlled metered dose oral inhaler (SmartMist, Aradigm Corporation) could deliver fentanyl in a way suitable for control of severe pain.

METHODS

Aersolised pulmonary fentanyl base 100-300 microg was administered to healthy volunteers using SmartMist and the resultant plasma concentration-time data were compared with those from the same doses administered by intravenous (i.v.) injection in the same subjects.

RESULTS

Plasma concentrations from SmartMist were similar to those from i.v. injection. Time-averaged bioavailability based upon nominal doses averaged approximately 100%, and was > 50% within 5 min of delivery. Fentanyl systemic pharmacokinetics were similar to those previously reported with no trends to dose-dependence from either route. Side-effects (e.g. sedation, lightheadedness) were the same from both routes.

CONCLUSIONS

Fentanyl delivery using SmartMist can provide analgetically relevant plasma drug concentrations. This, combined with its ease of noninvasive use and transportability, suggests a strong potential for field and domicilliary use, and for patient controlled analgesia without the need for i.v. cannulae.

Morphine pharmacokinetics after pulmonary administration from a novel aerosol delivery system

BACKGROUND

Successful pharmacotherapy of pain often depends on the mode of drug delivery. A novel, unit dose, aqueous aerosol delivery system (AERx Pulmonary Drug Delivery System) was used to examine the feasibility of the pulmonary route for the noninvasive systemic administration of morphine.

METHODS

The study had two parts: (1) a dose-ranging study in four subjects with three consecutive aerosolized doses of 2.2, 4.4, and 8.8 mg (nominal) morphine sulfate pentahydrate at 40-minute intervals, and (2) a crossover study, on separate days, in six subjects with 4.4 mg (nominal) aerosolized morphine sulfate administered over 2.1 minutes on three occasions and intravenous infusions of 2 and 4 mg over 3 minutes. Subjects were healthy volunteers from 19 to 34 years old. Arterial blood was sampled for a total of 6 hours and plasma morphine concentrations were measured by gas chromatography-mass spectrometry.

RESULTS

In part 1, plasma morphine concentrations were proportional to dose. In part 2, the mean +/- SD peak plasma concentration (Cmax) occurred at 2.7 +/- 0.8 minutes after the aerosol dose, with mean values for Cmax of 109 +/- 85, 165 +/- 22, and 273 +/- 114 ng/ml for the aerosol and 2 and 4 mg intravenous doses, respectively. The bioavailability [AUC(0-360 min)] of aerosol-delivered morphine was approximately 100% relative to intravenous infusion, with similar intersubject variability in AUC for both routes (coefficient of variation < 30%).

CONCLUSION

The time courses of plasma morphine concentrations after pulmonary delivery by the AERx system and by intravenous infusions were similar. This shows the utility of the pulmonary route in providing a noninvasive method for the rapid and reproducible systemic administration of morphine if an appropriate aerosol drug delivery system is used.

Intratracheal administration of fentanyl: pharmacokinetics and local tissue effects

OBJECTIVE

To study the pharmacokinetics and local tissue effects resulting from the intratracheal administration of preservative-free fentanyl.

DESIGN

Prospective, randomized, blinded and controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Eighteen adult male New Zealand rabbits.

INTERVENTIONS

Preservative-free fentanyl citrate or normal saline was administered by the intratracheal (i.t.) and intravenous (i.v.) routes to randomized groups of rabbits. The animals were killed at 24, 48 and 72 h following administration.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of fentanyl were measured before administration and at 2, 5, 10, 30, 60 and 120 min following administration by a specific radioimmunoassay. A detailed histological examination of the lung and tracheal tissue was performed to identify local side effects. There were no significant differences in the plasma fentanyl concentrations resulting from the i.v. or i.t. route of administration. In both groups, the concentrations of fentanyl were within the therapeutic range (i.t. 2.37 ng/ml, i.v. 2.53 ng/ml) by 2 min after injection and reached a maximum concentration within 5 min. The bioavailability of i.t. fentanyl was 71%. Microscopic examination of the respiratory system did not show significant differences between the two random groups overall. However, in the sub-group of animals killed at 24 h, more animals in the i.t. group showed signs of inflammation in the lung parenchyma.

CONCLUSIONS

There is rapid absorption of fentanyl following i.t. administration. Pharmacokinetic parameters for fentanyl were not significantly altered by the route of administration. Although there were no signs that i.t. administration of preservative-free fentanyl produces lung injury, a transient and mild inflammatory response was detected at 24 h after administration.

Acute pain management

Analgesic regimens should be based on sound clinical data and tailored to the individual patient's needs. The combination of specific agents for selected syndromes and traditional analgesics allows safe pain relief to be achieved for most emergency patients.