"his prescribed" is correct and usable in written English.
You can use it when you want to refer to something that has been designated or recommended for someone by a doctor, authority figure, or rule. Example: He diligently followed his prescribed medication regimen, and his health gradually improved.
His prescribed script had been torn up.
Earlier in the fall, he had started shortening the time between his prescribed doses of Percocet until suddenly he was taking twice what he should.
Mikal had told me that his prescribed respiratory routine would distract my mind from the impending puncture and align my yin better with my yang.
At Brooklyn Hospital, doctors diagnosed early stages of pneumonia and found that Mr. Washington had been unknowingly taking only half his prescribed dosage of medicine since his pharmacy recently switched brands.
Wakeling informed staff yesterday of his forthcoming surgery and that he intends to spend all his spare time - of which there will be plenty during his prescribed bed rest - watching television.
You might think that the mood this political season is being set by the likes of Glenn Beck or Sarah Palin or even that nobody pastor in Florida who outlasted his prescribed 15 minutes.
Perhaps it was the long menu of medications his doctors prescribed: narcotics to ease his pain, antipsychotics to control his moods, sleep aids to tame his nightmares.
Scouted on the street in England, the 17-year-old met success so quickly that the orthodontics his agents prescribed unexpectedly became his calling card.
Appearing on a steady stream of national television programs, he has defended plural marriage as a fulfillment of his Mormon religion as his ancestors prescribed it.
Even before Nungesser was finished using the three-week supply of drops his doctor prescribed after the surgery, his world came roaring back.
His doctor prescribed him Adderall to treat his symptoms, but higher and higher doses of the stimulant failed to have an effect.
