So the specifics are China that is now strictly controlling a small set of advanced piperidone/piperidine intermediates plus two broad families of derivatives that cover most of the “last mile” steps into fentanyl. Some upstream raw chemicals are still wide open, like aniline and propionyl chloride, along with other basic lab reagents. So technically nobody banned the entire pipeline, but this does clamp down on several of the most convenient rate-limiting steps cartel labs were relying on.
There's no expected impact on prices for medical fentanyl.