Although I see the convenience of weight field, wouldn’t it be more reasonable to keep this information as an entry in the measurement table? At the very least, allowing it as a 50 length varchar just asks for trouble.
On a more general note, current drug domain toolset, to my knowledge, is not currently used in actual use-cases beyond Ingredient level, which is used for drug_era table creation. Dosage and route information ends up being unused. Is there a need for more precise drug information now?