Pharmacokinetics of fentanyl after subcutaneous administration in volunteers:

Subcutaneous vs intravenous fentanyl for labor pain management: a multicenter randomized controlled trial

BACKGROUND

Labor pain is the most intense pain a woman will experience during her lifetime. Epidural anesthesia is recommended as the most effective method for pain relief, but it has several limitations. Fentanyl has high analgesic potency with short-acting duration, but the large-scale trials that assessed the effectiveness and safety of it for labor pain management are still limited.

OBJECTIVE

This study aimed to compare the effectiveness and harm and maternal satisfaction of subcutaneous vs intravenous fentanyl for labor pain management.

STUDY DESIGN

We conducted a multicenter, open-label randomized controlled trial. A total of 226 women were randomized to receive intravenous or subcutaneous fentanyl for labor pain management. Pain scores were evaluated before and after fentanyl administration at 5, 30, and 60 minutes and then every 60 minutes until delivery. The data were analyzed based on the intention-to-treat principle.

RESULTS

Both intravenous and subcutaneous fentanyl significantly decreased labor pain from baseline to delivery (overall mean change, -1.39; 95% confidence interval, -1.62 to -1.17; and -0.89; 95% confidence interval, -1.24 to -0.05, respectively). The reduction in the pain score between the 2 groups was not different (overall mean difference, -0.35; 95% confidence interval, -0.76 to 0.05). Maternal satisfaction was high for both intravenous and subcutaneous fentanyl (89.4% and 93.8%, respectively). There was no difference in the maternal satisfaction rate between the 2 groups (relative risk, 0.95; 95% confidence interval, 0.88-1.03). No serious maternal and neonatal adverse effects were observed.

CONCLUSION

Both intravenously and subcutaneously administered fentanyl were safe and significantly reduced pain from baseline to delivery among low-risk pregnancies. Maternal satisfaction with the childbirth experience was high regardless of the route of administration of fentanyl. No serious adverse effects of fentanyl were observed in either the mothers or the neonates.

Sentanyl: a comparison of blood fentanyl concentrations and naloxone dosing after non-fatal overdose

INTRODUCTION

Non-pharmaceutical fentanyl and its analogs have driven striking increases in opioid-associated overdose deaths. These highly potent opioids can be found at low concentrations in biological specimens. Little is known regarding the concentrations of these substances among survivors of non-fatal overdoses. In a locale where fentanyl is responsible for the majority of non-fatal opioid overdoses, we compared the concentration of fentanyl in blood to naloxone dosing in the presence and absence of a concurrent sedative-hypnotic exposure.

METHODS

In this pilot study, we enrolled adult patients presenting to the emergency department (ED) who: (1) arrived after an overdose requiring naloxone for the reversal of respiratory depression; and (2) who required venipuncture or intravenous access as part of their clinical care. Blood specimens (n = 20) underwent comprehensive toxicology testing, including the quantitation of fentanyl, fentanyl analogs, and naloxone, as well as the detection of common sedative-hypnotics and a wide range of other illicit and pharmaceutical substances. We then compared fentanyl concentrations to naloxone dosing in participants with and without a concomitant sedative-hypnotic exposure.

RESULTS

Nineteen of twenty participants (95%) were exposed to fentanyl prior to their overdose; the remaining participant tested positive for heroin metabolites. No participants reported pharmaceutical fentanyl use. Fentanyl analogs - acetylfentanyl or carfentanil - were present in three specimens. In 11 cases, fentanyl and its metabolites were the only opioids identified. Among the fentanyl-exposed, blood concentrations ranged from <0.1-19 ng/mL with a mean of 6.2 ng/mL and a median of 3.6 ng/mL. There was no relationship between fentanyl concentration and naloxone dose administered for reversal. We detected sedative-hypnotics (including benzodiazepines, muscle relaxants, and antidepressants) in nine participants. Among the sedative-hypnotic exposed, fentanyl concentrations were lower, but naloxone dosing was similar to those without a concomitant exposure.

CONCLUSIONS

In this study, we found that: 1) fentanyl was present in the blood of nearly all participants; 2) fentanyl concentrations were lower among study participants with concomitant sedative-hypnotic exposure; and 3) the dose of naloxone administered for overdose reversal was not associated with the measured fentanyl concentration in blood specimens. Our results underscore the role that tolerance and concomitant drug exposure play in the precipitation and resuscitation of management of opioid overdose.

Population pharmacokinetic model of subcutaneous fentanyl in older acute care patients

PURPOSE

Subcutaneous fentanyl injection is commonly prescribed to manage acute pain in older patients; however, there is a gap in the literature describing the pharmacokinetic parameters for this route of administration in this population. The aim of this study was to develop and evaluate a population pharmacokinetic model for subcutaneous fentanyl injection in older patients.

METHODS

Twenty-one patients who received subcutaneous fentanyl injections (50 to 75 μg) were recruited. Fentanyl concentrations were determined using a validated liquid chromatography/tandem mass spectrometry method. A population pharmacokinetic model was developed using non-linear mixed-effects modelling. A base model was selected based on the Akaike information criterion. Age, sex, body weight, number of previous fentanyl doses, number of prescribed medications, creatinine clearance, Charlson Comorbidity Index, Identification of Seniors at Risk score and concurrent use of CYP3A4 inhibitors were covariates considered for inclusion. A p value of < 0.05 was considered statistically significant for inclusion of covariates in the final model by stepwise addition. The simulation performance of the model was assessed by visual predictive check.

RESULTS

A one-compartment, first-order absorption with lag time and linear elimination model was the best to fit to the fentanyl concentration data. The absorption rate constant was 0.136 h^-1 (between subject variability (BSV), 46%), lag time 0.66 h (BSV 51%), apparent volume of distribution 6.28 L (BSV 30%), and apparent clearance 16.3 L.h^-1 (BSV 54%). The Charlson Comorbidity Index was the only covariate included in the final model, where a higher value of the index increased fentanyl exposure and C_max.

CONCLUSION

This is the first report of subcutaneous fentanyl population pharmacokinetic model to evaluate fentanyl pharmacokinetic in older patients. The between subject variability in clearance and subcutaneous absorption rate was relatively high, and some patients recorded high fentanyl concentrations in the context of their titration to effect.

Subcutaneous fentanyl for labour analgesia: a retrospective case note review

BACKGROUND

In 2017, a South Australia Perinatal Practice Guideline was introduced state-wide for the use of subcutaneous fentanyl for labour analgesia as a replacement for intramuscular pethidine. We retrospectively reviewed the implementation of this practice change in our institution.

METHODS

A retrospective review of maternal and neonatal case notes for the first 100 women administered subcutaneous fentanyl in labour at a single tertiary referral centre for maternity care, between February and June 2017.

RESULTS

Of the 102 women administered subcutaneous fentanyl, the majority (55%) were primipara, with an average maternal age of 29 years and body mass index of 27 kg/m². The median total fentanyl dose administered was 200 µg and the average time from last dose to birth was 3 h. The majority of women (70%) did not require additional rescue labour analgesia and 80% had a spontaneous vaginal birth. All neonates had a 5-min Apgar score >7. The median Apgar score at 1 and 5 min was 9. No neonate had an arterial cord blood pH <7.1. The mean arterial and venous cord blood pH was 7.3. The average time for neonates to establish breathing was 1 min and the median postnatal length of stay was two days.

CONCLUSIONS

Subcutaneous fentanyl for labour analgesia appears effective and has a low incidence of adverse events.

Intranasal Fentanyl versus Subcutaneous Fentanyl for Pain Management in Prehospital Patients with Acute Pain: A Retrospective Analysis

Objective: Retrospective analysis evaluating and comparing the feasibility, effectiveness and safety of intranasal fentanyl (INF) and subcutaneous fentanyl (SCF) for pain management of patients with acute severe pain in a rural/suburban Emergency Medical Services (EMS) system. Methods: Pre- and post-pain management data of all patients (aged ≥14 years) who were transported to the emergency department (January 2015-August 2017) were extracted from EMS and online medical control center records, and compared for groups receiving INF or SCF. Kaplan-Meier analysis and the log-rank test were used to describe and compare the percentage of patients in both groups who experienced relief according to their clinically significant pain relief score. Subgroup analysis was performed by patient age (<70 years, ≥70 years). Results: 94.6% (SCF = 94.8%; INF = 94.4%) of patients successfully received fentanyl and 82.7% (SCF = 81.2%; INF = 84.0%) had complete data and were included in the analysis. No difference was observed in time to administration or in the effectiveness of INF and SCF, and neither route of administration resulted in major adverse events that required intervention by paramedics. Upon subgroup analysis, INF patients ≥70 years were more likely to experience relief compared to those <70 years. Conclusion: This retrospective analysis of prehospital patients in the Chaudière-Appalaches EMS system demonstrates that both IN and SC are feasible, effective and safe routes for administering fentanyl. The observed effects of INF were found to be greater among patients ≥70 years. Further research is required to compare these routes with more conventional methods of pain management.

Effect of fentanyl nasal packing treatment on patients with acute postoperative pain after closed reduction of nasal bone fracture: a randomized double-blind controlled trial

PURPOSE

Nasal bone fracture reduction surgery is normally followed by nasal packing to control bleeding. Yet, patients suffer from pain and require further analgesic treatments following nasal packing and removal. This study aimed to evaluate the effect of fentanyl-soaked packing as a method of controlling pain after nasal surgeries in a prospective, randomized, double-blind controlled trial.

METHODS

Sixty-five patients that have undergone closed nasal bone fracture reduction surgery were included in this study. Thirty-two patients were treated postoperatively with 50 mcg fentanyl-soaked Merocel^®, a biodegradable synthetic polyurethane foams packing, and the other 33 patients were treated with saline-soaked packings. To analyze the relative nasal pain control effect of fentanyl, Numeric Rating Scale, patient satisfaction and Ramsay Sedation Scale were used. Patients were closely monitored to record relevant cardiopulmonary indicators and degree of adverse symptoms such as headache or sore throat.

RESULTS

Fentanyl group had a significantly lower Numeric Rating Scale and higher patient satisfaction for most of the time periods after operation (p < .05). Symptoms of headache and sore throat were also significantly reduced. Ramsay Sedation Scale scores improved compared to the control group (p < .05). No significant differences in cardiopulmonary relevant indicators between the two experimental groups were observed (p > .05).

CONCLUSION

Fentanyl-soaked packing significantly decreased postoperative pain with no observable adverse effects. Our results demonstrate that topical fentanyl application to nasal packing is an effective method of postoperative pain control after closed nasal bone fracture reduction surgery.

Effect of Fentanyl Nasal Packing Treatment on Patients With Acute Postoperative Pain After Nasal Operation: A Randomized Double-Blind Controlled Trial

PURPOSE

Nasal packing is an option for bleeding control after endoscopic sinus surgery and septoplasty. Although new packing materials have been developed, patients still suffer from pain and require additional analgesics treatments. In this study, a prospective, randomized, and double-blind controlled trial was designed to evaluate the effect of fentanyl-soaked packing on pain after endoscopic sinus surgery and septoplasty.

METHODS

One hundred fifty-two patients who underwent nasal surgeries due to chronic rhinosinusitis or nasal septal deviation were enrolled in this study. At the end of operation, 50 mcg fentanyl-soaked biodegradable synthetic polyurethane foams packing Nasopore or Merocel were applied to a group of 79 patients, and saline-soaked ones were applied to another group of 73 patients. To evaluate the influence of fentanyl on postoperative nasal pain, patients' conditions were assessed via means of Numeric Rating Scale, patient satisfaction, and Ramsay Sedation Scale. In addition, symptoms of headache or sore throat and any signs of cardiopulmonary-relevant indicators were monitored.

RESULTS

The fentanyl group had significantly decreased Numeric Rating Scale and increased patient satisfaction in every operation type for the majority of postoperative time periods ( P < .05) with reduced postoperative headache and sore throat compared to the control group. The fentanyl group showed a higher score on Ramsay Sedation Scale than the control group ( P < .05 in group including endoscopic sinus surgery). There were no significant differences in cardiopulmonary-relevant indicators between the 2 groups ( P > .05).

CONCLUSION

Fentanyl group showed significantly reduced postoperative pain without serious adverse effects. We suggest that topical fentanyl application to nasal packs can be a useful method to reduce pain during the early postoperative period after endoscopic sinus surgery and septoplasty.

A randomized controlled trial comparing the effect of intravenous, subcutaneous, and intranasal fentanyl for pain management in patients undergoing cesarean section

BACKGROUND

The objective of this study was to evaluate and compare the effects of three methods of using intravenous (IV), subcutaneous and intranasal (IN) fentanyl for pain management following general anesthesia in patients undergoing cesarean section.

MATERIALS AND METHODS

A prospective, randomized, single-blind clinical trial was done on 75 patients aged 20-40 years, American Society of Anesthesiology-1, who had a normal singleton pregnancy beyond 36 weeks of gestational age. Patients were randomized to receive 50 μg fentanyl intravenously (Group 1), subcutaneously (Group 2) or intranasally (Group 3) after closure of incision. The pain intensity, nausea, the systolic, and diastolic blood pressures were assessed.

RESULTS

All groups were equivalent for baseline characteristics. The average pain visual analog scale (VAS) score was less in the second group who received fentanyl subcutaneously at the time of recovery admission (6.8 ± 1.5) (P = 0.037) and after 3 h (6.36 ± 1.5) (P = 0.033) postoperatively. The mean VAS score of nausea and the mean systolic and diastolic blood pressures were not significantly different between three groups throughout the study (P > 0.05).

CONCLUSION

subcutaneous fentanyl is an effective alternative to IV and IN route of administration for pain management.

Treatment with subcutaneous and transdermal fentanyl: results from a population pharmacokinetic study in cancer patients

Purpose

Transdermal fentanyl is effective for the treatment of moderate to severe cancer-related pain but is unsuitable for fast titration. In this setting, continuous subcutaneous fentanyl may be used. As data on the pharmacokinetics of continuous subcutaneous fentanyl are lacking, we studied the pharmacokinetics of subcutaneous and transdermal fentanyl. Furthermore, we evaluated rotations from the subcutaneous to the transdermal route.

Methods

Fifty-two patients treated with subcutaneous and/or transdermal fentanyl for moderate to severe cancer-related pain participated. A population pharmacokinetic model was developed and evaluated using non-linear mixed-effects modelling. For rotations from subcutaneous to transdermal fentanyl, a 1:1 dose conversion ratio was used while the subcutaneous infusion was continued for 12 h (with a 50 % tapering after 6 h). A 6-h scheme with 50 % tapering after 3 h was simulated using the final model.

Results

A one-compartment model with first-order elimination and separate first-order absorption processes for each route adequately described the data. The estimated apparent clearance of fentanyl was 49.6 L/h; the absorption rate constant for subcutaneous and transdermal fentanyl was 0.0358 and 0.0135 h⁻¹, respectively. Moderate to large inter-individual and inter-occasion variability was found. Around rotation from subcutaneous to transdermal fentanyl, measured and simulated plasma fentanyl concentrations rose and increasing side effects were observed.

Conclusions

We describe the pharmacokinetics of subcutaneous and transdermal fentanyl in one patient cohort and report several findings that are relevant for clinical practice. Further research is warranted to study the optimal scheme for rotations from the subcutaneous to the transdermal route.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-015-2005-x) contains supplementary material, which is available to authorized users.

Pharmacokinetics of tramadol after subcutaneous administration in a critically ill population and in a healthy cohort

Background

Tramadol is an atypical centrally acting analgesic agent available as both oral and parenteral preparations. For patients who are unable to take tramadol orally, the subcutaneous route of administration offers an easy alternative to intravenous or intramuscular routes. This study aimed to characterise the absorption pharmacokinetics of a single subcutaneous dose of tramadol in severely ill patients and in healthy subjects.

Methods/design

Blood samples (5 ml) taken at intervals from 2 minutes to 24 hours after a subcutaneous dose of tramadol (50 mg) in 15 patients (13 male, two female) and eight healthy male subjects were assayed using high performance liquid chromatography. Pharmacokinetic parameters were derived using a non-compartmental approach.

Results

There were no statistically significant differences between the two groups in the following parameters (mean ± SD): maximum venous concentration 0.44 ± 0.18 (patients) vs. 0.47 ± 0.13 (healthy volunteers) mcg/ml (p = 0.67); area under the plasma concentration-time curve 177 ± 109 (patients) vs. 175 ± 75 (healthy volunteers) mcg/ml*min (p = 0.96); time to maximum venous concentration 23.3 ± 2 (patients) vs. 20.6 ± 18.8 (healthy volunteers) minutes (p = 0.73) and mean residence time 463 ± 233 (patients) vs. 466 ± 224 (healthy volunteers) minutes (p = 0.97).

Conclusions

The similar time to maximum venous concentration and mean residence time suggest similar absorption rates between the two groups. These results indicate that the same dosing regimens for subcutaneous tramadol administration may therefore be used in both healthy subjects and severely ill patients.

Trial registration

ACTRN12611001018909

Effects of prophylactic subcutaneous fentanyl on exercise-induced breakthrough dyspnea in cancer patients: a preliminary double-blind, randomized, controlled trial

CONTEXT

Dyspnea is one of the most distressing symptoms in patients with cancer, and often worsens with breakthrough episodes on exertion. We hypothesized that fentanyl given prophylactically may alleviate breakthrough dyspnea.

OBJECTIVES

To determine the feasibility of conducting a randomized trial of subcutaneous fentanyl in patients with cancer, and examine the effects of fentanyl on dyspnea, walk distance, vital signs, and adverse events.

METHODS

In this double-blind, randomized, controlled trial, we asked ambulatory patients with breakthrough dyspnea to perform a baseline six minute walk test (6MWT), and then assigned them to either subcutaneous fentanyl or placebo 15 minutes before a second 6MWT. We documented the change in dyspnea Numeric Rating Scale (NRS) score, walk distance, vital signs, and adverse events between the first and second 6MWT.

RESULTS

A total of 20 patients were enrolled (1:1 ratio) without attrition. Comparison between baseline and second walk showed that fentanyl was associated with significant improvements in dyspnea NRS score at the end of the 6MWT (mean [95% CI] -1.8 [-3.2, -0.4]), dyspnea NRS score at rest of 15 minutes after drug administration (-0.9 [-1.8, -0.04]), Borg Scale fatigue score at the end of the 6MWT (-1.3 [-2.4, -0.2]), 6MWT distance (+37.2m [5.8, 68.6]), and respiratory rate (-2.4 [-4.5, -0.3]). Nonstatistically significant improvements also were observed in the placebo arm, with no difference between the two study arms. No significant adverse effects were observed.

CONCLUSION

Prophylactic fentanyl was safe and improved dyspnea, fatigue, walk distance, and respiratory rate. We also observed a large placebo effect. Our results justify larger randomized controlled trials with higher fentanyl doses (clinicaltrials.gov registration: NCT01515566).

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).