Which of the following best describes a therapeutic drug?

A therapeutic drug is defined as a substance that is specifically designed or used to treat, prevent, or alleviate the symptoms of an illness or medical condition. This is why the option indicating a drug that has a medical purpose is the correct choice.

Therapeutic drugs are critical in the healthcare system as they help in managing diseases, improving patient health, and enhancing the quality of life. They can range from antibiotics used to fight infections to medications that manage chronic conditions like diabetes or hypertension.

In contrast, options that describe a drug with no medical purpose or those used exclusively for recreational use do not fit the definition of a therapeutic drug because they lack the intended medical benefits. Additionally, a drug used only in emergency situations may not be therapeutic in nature, as it implies a specific context rather than an overall medical application. This reflects the broader scope of therapeutic drugs, which are utilized in a variety of clinical settings beyond emergencies.