Structural study of anhydrous and hydrated 5-fluorouracil co-crystals with nicotinamide and isonicotinamide

Abstract 5-Fluorouracil is a widely used anti-cancer drug which exhibits diverse polymorphic and co-crystalline behavior. Here we report two new solvent-free co-crystals of 5-fluorouracil with model co-formers nicotinamide and isonicotinamide, along with the redetermination of their hydrated analogues. Selected co-formers are categorized as safe and therefore suitable for pharmaceutical applications. Differences and similarities in supramolecular topology of the given structures are discussed. A special emphasis is set on the influence of fluorine moieties on the overall packing and synthetic accessibility of the presented multi-component systems.