Pharmacology Update
Naloxone Hydrochloride Injection (Evzio)
By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD
Dr. Elliott is Chair, Formulary Committee, Northern California Kaiser Permanente; and Assistant Professor
of Medicine, University of California, San Francisco.
Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA.
Drs. Elliott and Chan report no financial relationships relevant to this field of study.
The fda has approved the first naloxone hand-held auto-injector. It is intended for family members or caregivers to treat suspected opioid overdose. The auto-injector can be carried in a pocket or stored in a medicine cabinet. The product was reviewed under the agency’s priority review program. It is marketed by Kaleo, Inc. as Evzio.
Indication
Naloxone, an opioid antagonist, is indicated for the emergency treatment of known or suspected opioid overdose.1 Signs of overdose are respiratory and/or central nervous system depression.
Dosage
The initial dose is 0.4 mg of naloxone hydrochloride delivered by the prefilled auto-injector into the muscle or under the skin. Repeated doses may be needed depending on the amount, type, and rate of administration of the opioid exposure. Immediate medical attention should be sought after injection. Evzio comes with printed instructions as well as electronic voice instructions.
Potential Advantages
This formulation is intended to be given by family members or caregivers allowing for early administration outside a health care setting. The device comes with step-by-step voice instructions, similar to a defibrillator. The drug may be blindly injected in the thigh, through clothing if necessary.
Potential Disadvantages
Abrupt reversal of opioid depression may result in nausea, vomiting, sweating, accelerated heart rate, trembling, increased blood pressure, seizures, and cardiac arrest.2 Naloxone has limited efficacy if respiratory depression is caused by partial agonist or mixed agonist/antagonists such as buprenorphine and pentazocine. Use of naloxone in opioid-dependent individuals may precipitate an acute abstinence syndrome. Naloxone has a shorter duration of action than many opioids, so repeated doses may be needed.
Comments
The approval of naloxone auto-injector was based on demonstration of bioequivalence to naloxone injection using a standard syringe.2 This demonstrated that the auto-injector delivered naloxone to the systemic circulation compared to that delivered by a standard syringe/needle. The design was a randomized, two-period crossover study in 30 healthy subjects. The endpoints were the peak concentration (Cmax) and area under the plasma time curve (AUC). The AUC for the auto-injector was the same as given by a standard syringe. The Cmax was 15% higher.
Clinical Implication
Someone dies every 36 minutes in the United States from illicit or prescription opioid overdose. Due to the major public health concern regarding overdose and death from misuse and abuse of illicit and prescription opioids, the FDA fast tracked the approval of Evzio 2 months before it was scheduled to be approved. The drug’s approval was a result of efforts by several federal agencies and has been the subject of a joint Health and Human Services and FDA working group and has been a part of the White House’s Office of National Drug Control Policy’s National Drug Control Strategy.3 Evzio has the potential to prevent death from an opioid overdose in the field, stabilizing the patient until emergency services arrive. The cost for Evzio was not available at the time of this review.
References
- Evzio Prescribing Information. Richmond, VA: Kaleo, Inc.; April 2014.
- Center for Drug Evaluation and Research. Application number 205787Orig1s000. Summary Review. April 2014.
- http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm391465.htm. Accessed on April 20, 2014.
