A muscle that works in concert with an AGONIST muscle to perform a certain movement.
An agent, for example a drug, that acts with another to produce a result that is greater than adding together the separate effects of the two agents. Synergism in drug treatment may be beneficial, as in the case of combined LEVODOPA and SELEGILINE, a selective monoamine oxidase inhibitor (see MONOAMINE OXIDASE INHIBITORS (MAOIS), in the treatment of PARKINSONISM. It may be potentially dangerous, however, as when MAOIs boost the effects of BARBITURATES.