Antonyms of noun inefficacy

1 sense of inefficacy

Sense 1
inefficacy, inefficaciousness -- (a lack of efficacy)
       Antonym of efficacy (Sense 1)
      => efficacy, efficaciousness -- (capacity or power to produce a desired effect; "concern about the safety and efficacy of the vaccine")

Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun inefficacy

1 sense of inefficacy

Sense 1
inefficacy, inefficaciousness -- (a lack of efficacy)
       => ineffectiveness, ineffectualness, ineffectuality -- (lacking the power to be effective)