The novel carboxamide–pyridine N-oxide synthon, sustained via N–H⋯O⁻ hydrogen bonding and C–H⋯O interaction, is shown to assemble isonicotinamide N-oxide in a triple helix architecture and the same heterosynthon is exploited to synthesize cocrystals of barbiturate drugs with 4,4′-bipyridine N,N′-dioxide.