How to Say "sleep-inducing" in Spanish
The Spanish word for “sleep-inducing” is “narcótico” — B2 level.

Examples
Algunas plantas tienen propiedades narcóticas muy fuertes.
Some plants have very strong narcotic properties.
El ritmo lento de la música tuvo un efecto narcótico en el público.
The slow rhythm of the music had a narcotic (sleep-inducing) effect on the audience.
Su voz era suave y casi narcótica.
His voice was soft and almost narcotic.
Adjective Agreement
As a describing word, it must match the person or thing it describes. Use 'narcótico' for masculine things and 'narcótica' for feminine things.
Ending Agreement
Mistake: “Las plantas narcótico.”
Correction: Las plantas narcóticas. Remember that describing words must match the 'gender' and 'number' of what they describe.
Learn Spanish with Inklingo
Interactive stories, personalized learning, and more.