The antibiotic nitrofurantoin {systematic name: (E)-1-[(5-nitro-2-furyl)methylideneamino]imidazolidine-2,4-dione} is not only used for the treatment of urinary tract infections, but also illegally applied as an animal food additive. Since derivatives of 2,6-diaminopyridine might serve as artificial receptors for its recognition, we crystallized one potential drug-receptor complex, nitrofurantoin-2,6-diacetamidopyridine (1/1), C(8)H(6)N(4)O(5)·C(9)H(11)N(3)O(2), (I·II). It is characterized by one N-H···N and two N-H···O hydrogen bonds and confirms a previous NMR study. During the crystallization screening, several new pseudopolymorphs of both components were obtained, namely a nitrofurantoin dimethyl sulfoxide monosolvate, C(8)H(6)N(4)O(5)·C(2)H(6)OS, (Ia), a nitrofurantoin dimethyl sulfoxide hemisolvate, C(8)H(6)N(4)O(5)·0.5C(2)H(6)OS, (Ib), two nitrofurantoin dimethylacetamide monosolvates, C(8)H(6)N(4)O(5)·C(4)H(9)NO, (Ic) and (Id), and a nitrofurantoin dimethylacetamide disolvate, C(8)H(6)N(4)O(5)·2C(4)H(9)NO, (Ie), as well as a 2,6-diacetamidopyridine dimethylformamide monosolvate, C(9)H(11)N(3)O(2)·C(3)H(7)NO, (IIa). Of these, (Ia), (Ic) and (Id) were formed during cocrystallization attempts with 1-(4-fluorophenyl)biguanide hydrochloride. Obviously nitrofurantoin prefers the higher-energy conformation in the crystal structures, which all exhibit N-H···O and C-H···O hydrogen-bond interactions. The latter are especially important for the crystal packing. 2,6-Diacetamidopyridine shows some conformational flexibility depending on the hydrogen-bond pattern.