Isso é discutido (com detalhes consideráveis) no Jornada nas Estrelas: A Próxima Geração - Manual Técnico , considerado ser uma fonte canônica de informações sobre o universo de Star Trek.
Subcutaneous and intravenous administration of many types of
medication is accomplished with the hypospray. This device employs a
pinpoint high-pressure low-volume microscopic aerosuspension stream,
which permits low-viscosity medication to be administered through the
epidermis without mechanical penetration. Certain types of medications
can be formulated for a somewhat wider spray pattern, resulting in
lesser penetration into the epidermis, but yielding a higher rate of
absorption due to the greater skin area exposed to the drug.
Standard hyposprays are designed to accept a standard medication vial,
which can be changed as required. Field hyposprays are normally loaded
with an inert saline solution that serves as a vehicle fluid for any
of five user-selectable concentrated emergency medication ampules.
A Star Trek: Encyclopedia também oferece as seguintes informações, basicamente reiterando o texto acima.
Hypospray.
Medical instrument used by Starfleet medical personnel for subcutaneous and intramuscular administration of medication for many humanoid patients. The hypospray uses an extremely fine, high-pressure aerosuspension delivery system, eliminating the need for a needle to physically penetrate the skin.
Descendo a escala de cânones, o Manual de Referência Médica da Frota Estelar tem um painel inteiro que mostra o funcionamento interno de a " Seringa Hipodérmica de Spray de Ar ".