Commentary on Darke & Duflou (2016): Heroin-related deaths-identifying a window for intervention

Pharmacokinetic considerations for community-based dosing of nasal naloxone in opioid overdose in adults

INTRODUCTION

The administration of the opioid antagonist naloxone in the community is a measure to prevent death from opioid overdose. Approved nasal naloxone sprays deliver initial doses of 0.9 to 8 mg. The level of the initial community dose is controversial, as the scientific base is weak.In this review knowledge of the pharmacokinetics of nasal, both approved and improvised nasal sprays, and intramuscular naloxone will be utilized to evaluate dose-effect relationships in previous studies of opioid overdose outcomes.

AREAS COVERED

The aim was to present scientifically based considerations on the initial nasal naloxone doses currently available, which reasonably balances the effect and adverse outcomes, given that at least two doses are at hand. Also included in these considerations is the challenge by illicitly manufactured fentanyl and analogs.This paper is based on both peer-reviewed and grey literature identified by several searches, of such as naloxone pharmacokinetics/formulations/outcomes/emergency medical services, in PubMed and Embase.

EXPERT OPINION

There is little scientific evidence that supports the use of initial systemic dosing that exceeds 0.8 mg in the community. Higher doses increase the risk of withdrawal symptoms feared in people who use opioids. Many obstacles may reduce the potential of community-administered naloxone.

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.

Twenty years of take-home naloxone for the prevention of overdose deaths from heroin and other opioids-Conception and maturation

BACKGROUND

Opioid overdose is a major cause of mortality, but injury and fatal outcomes can be prevented by timely administration of the opioid antagonist naloxone. Pre-provision of naloxone to opioid users and family members (take-home naloxone, THN) was first proposed in 1996, and WHO Guidelines were issued in 2014. While widespread in some countries, THN is minimally available or absent elsewhere. This review traces the development of THN over twenty years, from speculative harm reduction proposal to public health strategy.

METHOD

Medline and PsycINFO were searched for peer-reviewed literature (1990-2016) using Boolean queries: 1) "naloxone OR Narcan"; 2) "(opioid OR opiate) AND overdose AND prevention". Grey literature and specialist websites were also searched. Data were extracted and synthesized as narrative review, with key events presented as chronological timeline.

RESULTS

Results are presented in 5-year intervals, starting with the original proposal and THN pilots from 1996 to 2001. Lack of familiarity with THN challenged early distribution schemes (2001-2006), leading to further testing, evaluation, and assessment of challenges and perceived medicolegal barriers. From 2006-2011, response to social and legal concerns led to the expansion of THN programs; followed by high-impact research and efforts to widen THN availability from 2011 to 2016.

CONCLUSIONS

Framed as a public health tool for harm reduction, THN has overcome social, clinical, and legal barriers in many jurisdictions. Nonetheless, the rising death toll of opioid overdose illustrates that current THN coverage is insufficient, and greater public investment in overdose prevention will be required if THN is to achieve its full potential impact.

Pharmacokinetics of concentrated naloxone nasal spray over first 30 minutes post-dosing: analysis of suitability for opioid overdose reversal

BACKGROUND AND AIMS

Lack of non-injectable naloxone formulations has impeded widespread take-home provision for the prevention of heroin/opioid overdose deaths. For non-injectable formulations that are finally being investigated, rapid onset of action and sufficient bioavailability will be vital. We present analysis of data from a study of concentrated naloxone nasal spray formulations. Our aims are: to assess (1) pharmacokinetic properties and (2) suitability for overdose reversal in terms of naloxone absorption within 30 minutes post-dosing.

DESIGN AND INTERVENTIONS/COMPARATOR

Open-label, randomized, four-way cross-over Latin-square pharmacokinetic study of naloxone administration by three routes: intranasal at two doses (8 mg/0.4 ml, 16 mg/0.4 ml) versus sublingual (16 mg/ml) versus intravenous reference (1 mg/ml).

SETTING

Clinical Pharmacology Unit at The Ohio State University (Columbus, OH, USA).

PARTICIPANTS

Twelve healthy volunteers (age 20-41; seven female).

MEASUREMENTS

From blood plasma naloxone concentrations, (1) standard pharmacokinetic parameters, including maximum plasma concentration (C_max ) and mean absolute bioavailability (F%, relative to intravenous injection), were determined; as well as (2) partial area under the curve (AUC) values, t_max (time to maximum plasma concentration) and t_50% (time to 50% of maximum plasma concentration) as measures of early absorption.

FINDINGS

(1) Bioavailability was F% = 25-28% for intranasal naloxone. Sublingual had low bioavailability (F% = 2%) and was not considered further. Mean C_max values for 8 mg (12.83 ng/ml) and 16 mg (18.25 ng/ml) intranasal exceeded 1 mg intravenous (9.64 ng/ml) naloxone. (2) Following intranasal administration, t_50% was reached within 8 minutes and t_max within 20 minutes. Mean naloxone absorption from dosing to 30 minutes (AUC₃₀ ) was greater following 8 mg (4.17 h × ng/ml) and 16 mg (5.91 h × ng/ml) intranasal than following 1 mg intravenous (1.70 h × ng/ml) administration.

CONCLUSIONS

Concentrated naloxone nasal spray has a promising pharmacokinetic profile, with substantial bioavailability. Its early absorption time-course suggests that concentrated nasal naloxone is suitable for emergency administration in the community, where rapid restoration of respiratory function is essential for opioid overdose reversal.