rare, generally limited to allergic reactions. it should be given if there is any suspicion of an opioid overdose. naloxone is available to the public in the united states in two routes of administration: intranasal and intramuscular/subcutaneous. intranasal forms include narcan, approved in 2015, and kloxxado, approved in 2021. formulations that are injectable into the intramuscular or subcutaneous spaces include evzio, approved in 2014, and zimhi, approved in 2021. the doses are approved for both children and adults and may be repeated every 2-3 minutes. synthetic opioids like fentanyl and carfentanil are much more potent than prescription opioids and heroin. there is some debate about whether increased doses of naloxone are required to reverse overdose from synthetic opioids, however this concern has prompted fda approval of higher dose naloxone formulations such as kloxxado and zimhi. if a person suspected of overdose regains consciousness, medical attention is still necessary. naloxone is temporary and people revived with the medication can stop breathing again. naloxone formulations for public use in the us brand name route of administration dose additional considerations narcan intranasal 4mg kloxxado intranasal 8mg evzio intramuscular/subcutaneous auto-injector 2mg zimhi intramuscular/subcutaneous prefilled syringe 5mg for individuals 12 years of age or older access to naloxone opioid overdose should be reversed as soon as possible. to shorten the time between overdose and naloxone administration, multiple programs have been enacted to improve naloxone access for drug users, caregivers, and first responders. these efforts include fda approval of intranasal and injectable naloxone over the counter, professional organizations recommending physicians to co-prescribe naloxone when opioids are used for pain management, free community overdose education and naloxone distribution (oend) programs, and efforts to train non-medical first responders such as firefighters and police to use naloxone. these actions have reduced opioid-related deaths at the state and national levels and are cost-effective. basic life support opioid overdose leads to death when people stop breathing. bystanders trained in first aid can evaluate people who have overdosed and provide basic life support including rescue breathing via bag valve mask or mouth to mouth. if the person who has overdosed does not have a pulse, rescuers should begin cpr. other treatments another medication that can be used to treat opioid overdoses is nalmefene, which is an opioid derivative structurally similar to naltrexone. it works similarly to naloxone but has a longer half life. it is approved for intravenous, intramuscular, and subcutaneous administration by prescription only, unlike the over the counter formulations of naloxone. epidemiology