Opioid overdose is a major public health crisis in the United States.   Treatment with naloxone has expanded, beyond use by clinicians in the hospital setting, but also beyond pre-hospital emergency medical services (EMS), into the general community.  It is critical that the available naloxone dose is consistently adequate for the emergency treatment of an opioid overdose and can be readily and rapidly administered by a first responder without exposure to needle-stick injury.  Adapt Pharma has developed NARCAN® Nasal Spray supplied as a single 4 mg dose of naloxone hydrochloride in a 0.1 mL intranasal spray.  Each Narcan 4 mg dose delivered by intranasal administration is approximately equivalent to a 2 mg dose of naloxone hydrochloride delivered by intramuscular injection (IM).  Narcan Nasal Spray is for intranasal administration only, in the treatment of suspected or known opioid overdose and frequently must be administered by someone other than a medically trained person.  This requires a simple, robust and easy to operate device.  The simplicity of the nasal spray was critical in device selection.  Selection of the chosen device was based on the small volume of liquid sprayed which remained in the nostril, 100 µL(microliters), regarded as the optimal for nasal administration and the higher naloxone concentration (40 mg/mL) which is optimal for nasal absorption. It is a single dose device that does not require priming before use and gives an orientation independent fine spray adhering to the nasal cavity wall, without the patient being alert.  This presentation briefly describes, the rationale and stages in developing Narcan Nasal Spray to achieve these needs.