Translation

効果的な / 効き目のある / 有効な

Meaning

Efficacious means producing the intended result, especially for a treatment, method, remedy, or policy. It is formal and often used when evidence of effectiveness matters. Do not confuse it with efficient, which focuses on low waste.

Examples

• その治療法は臨床試験で有効であることが示されました。
  The treatment proved efficacious in clinical trials.
• 委員会はより効果的な対策を求めました。
  The committee called for more efficacious measures.