Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pōtĭōno, no perf., ātum, 1, v. a. [1. potio], to give to drink (in the verb. finit. post class.): jumentum potione, Veg. Vet. 1, 46; 1, 34; 38; 3, 59: omnes gentes, Hieron. in Isa. 8, 27, v. 2.
Hence, pōtĭōnātus, a, um, P. a., that has had a potion given him (post-Aug.): potionatus amatorio medicamento, Suet. Calig. 50.