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

Reversal of Opioid-Induced Respiratory Depression in Healthy Volunteers: Comparison of Intranasal Nalmefene and Intranasal Naloxone

An open-label, randomized, crossover study in healthy volunteers compared the reversal of remifentanil-induced respiratory depression by intranasal (IN) naloxone hydrochloride (4 mg) to IN nalmefene (2.7 mg) (NCT04828005). Subjects were administered a hypercapnic gas mixture which produces an elevation in minute ventilation (MV), a result of the ventilatory response to hypercapnia. Subjects breathed a hypercapnic gas mixture through a tight-fitting mask for an initial period of 46 min prior to a series of mask "holidays" introduced to reduce subject discomfort and encourage study completion. Ten minutes after initiating the hypercapnic gas mixture, a remifentanil bolus was administered, and an infusion continued for the study duration. Subjects were administered either naloxone or nalmefene 15 min after initiating the remifentanil infusion and MV monitored for 21 min followed by a mask holiday. Both nalmefene and naloxone produced a time-dependent reversal of remifentanil-induced reductions in MV measured 2.5-20 min post administration. At the primary endpoint (5 min post administration), nalmefene increases in MV (5.75 L/min) were nearly twice that produced by naloxone (3.01 L/min) (P < .0009); the point estimate favors nalmefene, demonstrating non-inferiority and superiority. In this model of opioid-induced respiratory depression, nalmefene has a more rapid onset of action than naloxone, which required 20 min to achieve a comparable reversal of respiratory depression. Both nalmefene and naloxone were well tolerated by healthy volunteers. This rapid onset of action may prove particularly valuable in an era when over 90% of fatalities are linked to synthetic opioid overdose.

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.

Endogenous opiates and behavior: 2021

This paper is the forty-fourth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2021 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonizts and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Assessment of Neurotoxic Effects of Oxycodone and Naloxone in SH-SY5Y Cell Line

Opioid drugs have analgesic properties used to treat chronic and post-surgical pain due to descending pain modulation. The use of opioids is often associated with adverse effects or clinical issues. This study aimed to evaluate the toxicity of opioids by exposing the neuroblastoma cell line (SH-SY5Y) to 0, 1, 10, and 100 µM oxycodone and naloxone for 24 h. Analyses were carried out to evaluate cell cytotoxicity, identification of cell death, DNA damage, superoxide dismutase (SOD), glutathione S-transferase (GST), and acetylcholinesterase (AChE) activities, in addition to molecular docking. Oxycodone and naloxone exposure did not alter the SH-SY5Y cell viability. The exposure to 100 µM oxycodone and naloxone significantly increased the cells' DNA damage score compared to the control group. Naloxone exposure significantly inhibited AChE, GST, and SOD activities, while oxycodone did not alter these enzymes' activities. Molecular docking showed that naloxone and oxycodone interact with different amino acids in the studied enzymes, which may explain the differences in enzymatic inhibition. Naloxone altered the antioxidant defenses of SH-SY5Y cells, which may have caused DNA damage 24 h after the exposure. On the other hand, more studies are necessary to explain how oxycodone causes DNA damage.

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.