Drugs can be classified according to their chemical composition or their intended therapeutic application. For instance, anti-infective agents that possess the ability to eliminate pathogens or suppress their growth and reproduction can be grouped based on the organisms they target or their chemical structure. Furthermore, drugs can be divided into prescription, nonprescription, or controlled substances. Prescription medications, such as antibiotics, require oversight from a licensed healthcare professional to minimize potential hazards and ensure safety. The FDA considers nonprescription or over-the-counter (OTC) drugs safe when used as instructed, eliminating the necessity for a prescription. OTC medications are frequently employed to relieve cold symptoms, provide analgesic effects, or address gastrointestinal issues. Due to their potential for abuse and addiction, controlled substances are rigorously regulated by the DEA and sorted into five schedules based on their potential for abuse, medical use, and safety:

Schedule I: High potential for abuse, no accepted medical use. For example, heroin and LSD.

Schedule II: High potential for abuse, accepted medical use with severe restrictions. For example, opioids and stimulants.

Schedule III: Lower potential for abuse, accepted medical use with less strict regulations, examples include certain opioid combinations.

Schedule IV: Lower potential for abuse, accepted medical use with fewer restrictions. For example, benzodiazepines.

Schedule V: Lowest potential for abuse, accepted medical use with minimal restriction. For example, certain cough medicines with codeine.

The classification helps regulate the distribution, use, and research of these substances to reduce potential harm and abuse.