Eur. Med. 1178 (and generally) πρὸς τὸν ἀρτίως πόσιν

Does the use of an adverb in a nominal phrase like πρὸς τὸν ἀρτίως πόσιν, indicate that we should imagine an appropriate verbal form (participle of a verb of marriage) when reading it, or does the adverb function temporarily as a differentbword class, ie serve as an adjective?