An apparatus includes a container, a needle, and an actuation assembly. The container contains a dose of a naloxone composition having a delivered volume of at least about 0.34 mL. The actuation assembly includes an energy storage member that produces a force on a movable member to move the needle and to deliver the dose of the naloxone composition. The 90% confidence interval of at least one of the relative mean maximum naloxone plasma concentration after dose delivery into the body (Cmax), time to reach the maximum naloxone plasma concentration (Tmax), area under the plasma concentration-time curve from pre-dose (time 0) extrapolated to infinity (AUC0-∞), or area under the plasma concentration-time curve from pre-dose (time 0) to the time of the last quantifiable concentration (Tlast) (AUC0-t) of the delivered dose to a delivered dose of a corresponding naloxone composition delivered via a manually-actuated syringe is within 80% to 125%.