Pharmacokinetics and Pharmacodynamics of a New Formulation of Nasal Naloxone for Prehospital Use

Overview

Overdose with potential deadly outcome is a serious problem among opioid abusers, not least in Norway. The annual death toll from overdose is about 250, higher than road traffic accidents. Those who inject heroin or other opioids are considered to have the highest risk for death from overdose. To save lives, immediate treatment with a μ-opioid antidote such as naloxone is required. Usually naloxone is injected into a muscle or a blood vessel. Administration of naloxone via the nose (intranasal) has been suggested as an alternative for use by emergency teams and possibly also bystanders. This is not only an easier way to give naloxone, but would also eliminate the risk for needle stick injuries and blood contamination. In a series of studies on intranasal naloxone at The Norwegian University of Science and Technology, this study explores pharmacokinetics and pharmacodynamics of intranasal and intramuscular naloxone in healthy volunteers under the influence of remifentanil.

Healthy volunteers will be brought into a state of opioid influence in a well-known, short acting, controlled and safe manner using remifentanil. Naloxone is a well-known, well-tolerated drug with an excellent safety profile over many decades of use. The current formulation has proven safe and without local or systemic side effects in the studies conducted so far. The excipients in the present nasal formulation are all well known. This study has two aims. Firstly to investigate what naloxone does to the body under opioid influence, applying a well-tested model with infusion of the potent opioid remifentanil (Target Control Infusion). This will create a state of strong opioid effect for a short time and in a highly controlled fashion, inducing a state of miosis, reduced respiratory rate and reduced sensation to pain, all three strong indicators of opiates. Naloxone will antagonise these effects, and this change can be measured. Choosing intramuscular 0.8 mg naloxone for comparison means that the novel intranasal naloxone formulation will be compared with the well-established and described treatment protocol for opioid overdose in Norway used today. Secondly the pharmacokinetic profile of intranasal and intramuscular naloxone will be studied. The same measurements as in preparative studies (OPI 12-001 and OPI 13-001) will be taken: Serum naloxone concentration over time to calculate maximum concentration, Time to maximum concentration, Area Under the Curve and Relative bioavailability. There are two main reasons to repeat these measurements. In contrast to the previous studies under the current protocol the participants will be under the influence by strong opioids. This may have significant physiologic effects, and it will be explored whether the pharmacokinetics of the intranasal formulation are changed. The other reason is that in this study pharmacokinetics of naloxone will be compared with the actual dosage and administration routes of naloxone as used by doctors and paramedics in the pre-hospital setting. This has not been done before, in spite of the widespread use of this treatment, The measurements of remifentanil in serum open the possibility to relate pharmacodynamic data directly to an actual serum concentration of the opioid at the same time. Care will be taken not to include opioid users in this study as naloxone would precipitate acute withdrawal. Also possible drug misusers will be excluded as well as people who have access to remifentanil and infusion equipment in their daily work, although the abuse potential of this highly specialised drug is minimal. Safety of the formulation will also be studied by measuring vital signs and for the patient to report any nasal discomfort or potential adverse reactions during the study. By weighing spray device, and intramuscular syringes before and after discharge the reliability of the dose delivered will be confirmed.