A dispensatory is a reference book that provides detailed information about medicinal drugs and their preparations. It includes descriptions of various substances, their uses, dosages, and methods of preparation. Dispensatories serve as essential resources for pharmacists and healthcare professionals in understanding the properties and applications of different medications. Historically, dispensatories have played a crucial role in the development of pharmacology. They often include information on the origins of drugs, their chemical compositions, and guidelines for compounding. The most well-known dispensatory in the United States is the United States Pharmacopeia (USP), which sets standards for medicines and their quality.