The hypospray is a medical device that injects drugs through the skin without a needle, standard equipment in Starfleet sickbays from the 22nd century onward.
Pressed against a patient's neck or arm, a hypospray delivers its dose with a quick hiss, making injections fast and painless. It can hold sedatives, stimulants, antidotes, vaccines and countless other medications.
Phlox used hyposprays aboard Enterprise NX-01, and McCoy, Crusher, Bashir and the Doctor all relied on them. In emergencies the device has also been used as an improvised weapon, a quick sedative being one of the most effective ways to subdue an unruly patient.