# Is this a passive construction?

Take the medicine as prescribed. As there is no verb to be in this sentence, is it passive because it is implied? ..i.e., Take the medicine as (it was) prescribed.?

• Yes, the passive construction takes an auxiliary be, and so do predicate adjectives formed from perfect participles, so the test usually is the grammaticality of an agent by-phrase. In the case of the OQ, the idiom is as prescribed (by indef doctor); i.e, as prescribed_and _as prescribed by a/your/the doctor are both grammatical and synonymous, so it is in fact a reduced passive clause. Participial and infinitive phrases are reduced clauses. – John Lawler May 29 '13 at 15:06