Definition of "direct-acting" [di•rect•-act•ing]

• Acting directly, as one part upon another, without the intervention of other working parts. (adjective)

Gnu Collaboartive International Dictionary of English: licensed under The Code Project Open License (CPOL)

• "It is advisable to use a direct-acting alpha-adrenergic agonist, such as norepinephrine, because their actions are not dependent upon the release of intracellular amines, the metabolism and availability of which are altered by MAO-I's."
• "Its key experimental medicine, Setrobuvir, is a direct-acting antiviral compound that is currently being evaluated by the U.S. company in a phase II study in combination with Roche's Pegasys and Copegus."
• "Biotron said BIT225 is the first in a new class of direct-acting antiviral drugs for hepatitis C, targeting a specific virus protein essential to virus production and replication."