Antonyms of adj inefficacious

1 sense of inefficacious

Sense 1
inefficacious (vs. efficacious) -- (lacking the power to produce a desired effect; "laws that are inefficacious in stopping crime")

efficacious (vs. inefficacious) -- (marked by qualities giving the power to produce an intended effect; "written propaganda is less efficacious than the habits and prejudices...of the readers"-Aldous Huxley; "the medicine is efficacious in stopping a cough")
        => effective -- (works well as a means or remedy; "an effective reprimand"; "a lotion that is effective in cases of prickly heat")

Similarity of adj inefficacious

1 sense of inefficacious

Sense 1
inefficacious (vs. efficacious) -- (lacking the power to produce a desired effect; "laws that are inefficacious in stopping crime")
          Also See-> ineffective#1, uneffective#1, ineffectual#1