Comparison of a New Intranasal Naloxone Formulation to Intramuscular Naloxone: Results from Hypothesis-generating Small Clinical Studies

Clinical Pharmacokinetics and Pharmacodynamics of Naloxone

Naloxone is a World Health Organization (WHO)-listed essential medicine and is the first choice for treating the respiratory depression of opioids, also by lay-people witnessing an opioid overdose. Naloxone acts by competitive displacement of opioid agonists at the μ-opioid receptor (MOR). Its effect depends on pharmacological characteristics of the opioid agonist, such as dissociation rate from the MOR receptor and constitution of the victim. Aim of treatment is a balancing act between restoration of respiration (not consciousness) and avoidance of withdrawal, achieved by titration to response after initial doses of 0.4-2 mg. Naloxone is rapidly eliminated [half-life (t1/2) 60-120 min] due to high clearance. Metabolites are inactive. Major routes for administration are intravenous, intramuscular, and intranasal, the latter primarily for take-home naloxone. Nasal bioavailability is about 50%. Nasal uptake [mean time to maximum concentration (Tmax) 15-30 min] is likely slower than intramuscular, as reversal of respiration lag behind intramuscular naloxone in overdose victims. The intraindividual, interindividual and between-study variability in pharmacokinetics in volunteers are large. Variability in the target population is unknown. The duration of action of 1 mg intravenous (IV) is 2 h, possibly longer by intramuscular and intranasal administration. Initial parenteral doses of 0.4-0.8 mg are usually sufficient to restore breathing after heroin overdose. Fentanyl overdoses likely require higher doses of naloxone. Controlled clinical trials are feasible in opioid overdose but are absent in cohorts with synthetic opioids. Modeling studies provide valuable insight in pharmacotherapy but cannot replace clinical trials. Laypeople should always have access to at least two dose kits for their interim intervention.

The pharmacokinetic interaction between nasally administered naloxone and the opioid remifentanil in human volunteers

Purpose

Remifentanil has been shown to increase the bioavailability of nasally administered naloxone. The aim of this study was to explore the nature of this observation.

Methods

We analysed samples from three pharmacokinetic studies to determine the serum concentrations of naloxone-3-glucuronide (N3G), the main metabolite of naloxone, with or without exposure to remifentanil. To enable direct comparison of the three studies, the data are presented as metabolic ratios (ratio of metabolite to mother substance, N3G/naloxone) and dose-corrected values of the area under the curve and maximum concentration (Cmax).

Results

Under remifentanil exposure, the time to maximum concentration (Tmax) for N3G was significantly higher for intranasal administration of 71 min compared to intramuscular administration of 40 min. The dose-corrected Cmax of N3G after intranasal administration of naloxone under remifentanil exposure was significantly lower (4.5 ng/mL) than in subjects not exposed to remifentanil (7.8–8.4 ng/mL). The metabolic ratios after intranasal administration rose quickly after 30–90 min and were 2–3 times higher at 360 min compared to intravenous and intramuscular administration. Remifentanil exposure resulted in a much slower increase of the N3G/naloxone ratio after intranasal administration compared to intranasal administration with the absence of remifentanil. After remifentanil infusion was discontinued, this effect gradually diminished. From 240 min there was no significant difference between the ratios observed after intranasal naloxone administration.

Conclusion

Remifentanil increases the bioavailability of naloxone after nasal administration by reducing the pre-systemic metabolism of the swallowed part of the nasal dose.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00228-021-03190-1.

[Cardiac arrest under special circumstances]

These guidelines of the European Resuscitation Council (ERC) Cardiac Arrest under Special Circumstances are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the modifications required for basic and advanced life support for the prevention and treatment of cardiac arrest under special circumstances; in particular, specific causes (hypoxia, trauma, anaphylaxis, sepsis, hypo-/hyperkalaemia and other electrolyte disorders, hypothermia, avalanche, hyperthermia and malignant hyperthermia, pulmonary embolism, coronary thrombosis, cardiac tamponade, tension pneumothorax, toxic agents), specific settings (operating room, cardiac surgery, cardiac catheterization laboratory, dialysis unit, dental clinics, transportation [in-flight, cruise ships], sport, drowning, mass casualty incidents), and specific patient groups (asthma and chronic obstructive pulmonary disease, neurological disease, morbid obesity, pregnancy).

European Resuscitation Council Guidelines 2021: Cardiac arrest in special circumstances

These European Resuscitation Council (ERC) Cardiac Arrest in Special Circumstances guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the modifications required to basic and advanced life support for the prevention and treatment of cardiac arrest in special circumstances; specifically special causes (hypoxia, trauma, anaphylaxis, sepsis, hypo/hyperkalaemia and other electrolyte disorders, hypothermia, avalanche, hyperthermia and malignant hyperthermia, pulmonary embolism, coronary thrombosis, cardiac tamponade, tension pneumothorax, toxic agents), special settings (operating room, cardiac surgery, catheter laboratory, dialysis unit, dental clinics, transportation (in-flight, cruise ships), sport, drowning, mass casualty incidents), and special patient groups (asthma and COPD, neurological disease, obesity, pregnancy).

Take-Home Naloxone for the Emergency Interim Management of Opioid Overdose: The Public Health Application of an Emergency Medicine

Naloxone is a well-established essential medicine for the treatment of life-threatening heroin/opioid overdose in emergency medicine. Over two decades, the concept of 'take-home naloxone' has evolved, comprising pre-provision of an emergency supply to laypersons likely to witness an opioid overdose (e.g. peers and family members of people who use opioids as well as non-medical personnel), with the recommendation to administer the naloxone to the overdose victim as interim care while awaiting an ambulance. There is an urgent need for more widespread naloxone access considering the growing problem of opioid overdose deaths, accounting for more than 100,000 deaths worldwide annually. Rises in mortality are particularly sharp in North America, where the ongoing prescription opioid problem is now overlaid with a rapid growth in overdose deaths from heroin and illicit fentanyl. Using opioids alone is dangerous, and the mortality risk is clustered at certain times and contexts, including on prison release and discharge from hospital and residential care. The provision of take-home naloxone has required the introduction of new legislation and new naloxone products. These include pre-filled syringes and auto-injectors and, crucially, new concentrated nasal sprays (four formulations recently approved in different countries) with speed of onset comparable to intramuscular naloxone and relative bioavailability of approximately 40-50%. Choosing the right naloxone dose in the fentanyl era is a matter of ongoing debate, but the safety margin of the approved nasal sprays is superior to improvised nasal kits. New legislation in different countries permits over-the-counter sales or other prescription-free methods of provision. However, access remains uneven with take-home naloxone still not provided in many countries and communities, and with ongoing barriers contributing to implementation inertia. Take-home naloxone is an important component of the response to the global overdose problem, but greater commitment to implementation will be essential, alongside improved affordable products, if a greater impact is to be achieved.

Prepacked naloxone administration for suspected opioid overdose in the era of illicitly manufactured fentanyl: a retrospective study of regional poison center data

Background: Prepacked naloxone kits (PNKs) are frequently used to reverse opioid intoxication. It is unknown if the presence of illicitly manufactured fentanyl and its analogs (IMFs) in heroin supply is affecting the PNK doses given by laypersons. We investigated the trend of PNK dose administered to reverse opioid toxicity in suspected/undifferentiated opioid intoxication.Methods: We retrospectively reviewed PNK administrations reported to the Maryland Poison Center between 1 January 2015 and 15 October 2017. Primary outcome was the mean PNK dose administered to reverse opioid-induced central nervous system and ventilatory depression. Secondary outcomes included the reversal rate of opioid toxicity, patient disposition, and survival rate.Results: Our analysis involved 1139 PNK administrations. The mean age of subjects was 34.3 years; 68.8% (n = 781) were male. Ventilatory depression was present in 98.2% (n = 958) of cases, and 97% (n = 1097) were unresponsive. Law enforcement administered the majority of PNK (91.0%; n = 1035); the primary route was intranasal (97.9%; n = 1051). Toxicity was reversed in 79.2% (n = 886) of overdose victims after a mean PNK dose of 3.12 mg. EMS personnel gave 291 subjects additional naloxone (mean: 2.2 mg), reversing opioid toxicity in 94.2% (n = 254). Between 2015 and 2017, the mean PNK dose increased from 2.12 to 3.63 mg (p < .0001) while the reversal rate decreased from 82.1% to 76.4% (p = .04). One hundred and eighty-two patients (15.9%) refused transport; of those transported to a hospital, 73.4% (n = 569) were treated and released and 12.4% (n = 96) required hospitalization. Ninety-six percent (n = 1092) of the subjects survived. Forty subjects were pronounced dead at the scene. Fentanyl or its analog was detected in 36 of 55 opioid-related deaths (65.5%).Conclusions: PNK administration reversed toxicity in the majority of patients with undifferentiated opioid intoxication. Between 2015 and 2017, increasing doses of PNK were administered but the reversal rate decreased. These trends are likely multifactorial, including increasing availability of IMFs.

Naloxone formulation for overdose reversal preference among patients receiving opioids for pain management

BACKGROUND

Opioid-related overdose has increased 137% in the past decade. Training nonmedical bystanders to administer naloxone (Narcan™) is a widely-researched intervention that has been associated with decreases in overdose rates in the communities in which it has been implemented. A recent review advocated for noninjectable formulations of naloxone, however patient preference for naloxone formulations has not yet been examined (Strang et al., 2016).

METHODS

Two cohorts of respondents (N₁ = 501, N₂ = 172) who reported currently being prescribed an opioid for pain management were recruited through the crowd-sourcing program Amazon Mechanical Turk (MTurk) to assess their preference for naloxone formulations. All respondents were provided a description of different formulations and asked to indicate all formulations they would be willing to administer for overdose reversal and to then rank formulations in order of preference.

RESULTS

Results were remarkably similar across both cohorts. Specifically, respondents preferred noninjectable formulations (intranasal, sublingual, buccal) over injectable (intravenous, intramuscular) formulations. A small percent (8.9%-9.8%) said they would never be willing to administer naloxone. An identical percent of respondents in both cohorts (44.9%) rated intranasal as their most preferred formulation.

CONCLUSIONS

Two independent cohorts of respondents who were receiving opioid medications for pain management reported a preference for noninjectable over injectable formulations of naloxone to reverse an opioid overdose. Though initial preference is only one of many factors that impacts ultimate public acceptance and uptake of a new product, these results support the additional research and development of noninjectable naloxone formulations.

Pharmacodynamics and arteriovenous difference of intravenous naloxone in healthy volunteers exposed to remifentanil

PURPOSE

Pharmacodynamic studies of naloxone require opioid agonism. Steady state condition may be achieved by remifentanil TCI (target controlled infusion). Opioid agonism can be measured by pupillometry. It is not known whether there are arteriovenous concentration differences for naloxone. The aim was thus to further develop a model for studying pharmacokinetic/pharmacodynamic aspects of naloxone and to explore whether a significant arteriovenous concentration difference for naloxone in humans was present.

METHODS

Relevant authorities approved this study. Healthy volunteers (n = 12) were given 1.0 mg intravenous (IV) naloxone after steady state opioid agonism was obtained by TCI of remifentanil (1.3 ng/ml). Opioid effect was measured by pupillometry. Arterial and venous samples were collected simultaneously before and for 2 h after naloxone administration for quantification of naloxone and remifentanil.

RESULTS

Arterial remifentanil was in steady state at 12 min. One milligram IV naloxone reversed the effect of remifentanil to 93% of pre-opioid pupil-size within 4 min. The estimated duration of antagonism was 118 min. At that time, the concentration of naloxone was 0.51 ng/ml. The time course of arterial and venous serum concentrations for naloxone was similar, although arterial AUC (area under the curve) was slightly lower (94%) than the venous AUC (p = 0.03). There were no serious adverse events.

CONCLUSION

Onset of reversal by IV naloxone was rapid and lasted 118 min. The minimum effective concentration was 0.5 ng/ml. Using TCI remifentanil to obtain a steady-state opioid agonism may be a useful tool to compare new naloxone products.

Government Patent Use to Address the Rising Cost of Naloxone: 28 U.S.C. § 1498 and Evzio

The rising cost of the opioid antagonist and overdose reversal agent naloxone is an urgent public health problem. The recent and dramatic price increase of Evzio, a naloxone auto-injector produced by Kaléo, shows how pharmaceutical manufacturers entering the naloxone marketplace rely on market exclusivity guaranteed by the patent system to charge prices at what the market can bear, which can restrict access to life-saving medication. We argue that 28 U.S.C. § 1498, a section of the federal code that allows the government to use patent-protected products for its own purposes in exchange for reasonable compensation, could be used to procure generic naloxone auto-injectors, or at least bring Kaléo to the negotiating table. Precedent exists for the use of § 1498 to procure pharmaceuticals, and it could give meaning to the federal government's recent declaration of a public health emergency around the opioid epidemic, discourage new market entrants from charging exorbitant prices, and yield important public health benefits.

Pharmacokinetic properties of intranasal and injectable formulations of naloxone for community use: a systematic review

Aim: To assess the pharmacokinetic properties of community-use formulations of naloxone for emergency treatment of opioid overdose. Methods: Systematic literature review based on searches of established databases and congress archives. Results: Seven studies met inclusion criteria: two of US FDA-approved intramuscular (im.)/subcutaneous (sc.) auto-injectors, one of an FDA-approved intranasal spray, two of unapproved intranasal kits (syringe with atomizer attachment) and two of intranasal products in development. Conclusion: The pharmacokinetics of im./sc. auto-injector 2 mg and approved intranasal spray (2 and 4 mg) demonstrated rapid uptake and naloxone exposure exceeding that of the historic benchmark (0.4 mg im.), indicating that naloxone exposure was adequate for reversal of opioid overdose.