A pharmaceutical is a controlled chemical substance that is administered to a patient that is expected to have a therapeutic effect. The study of pharmaceuticals, their effects on patients, side effects and medicine interactions is called pharmacology. A pharmacist is an individual licensed to dispense pharmaceuticals that can only be given by a prescription by a physician and to give advice to patients on non-prescription pharmaceuticals.
In order to ensure that their effect on patients is consistent, pharmaceuticals are manufactured in identical batches and the active ingredient is kept as pure as possible, and uncontaminated. Often, the active ingredient will be combined with other materials to make it easier to administer to the patient, such as bindings, coatings and solutions.
The same active ingredient can be prepared and stored in different forms depending on how it must be administered to the patient. Many drugs can be administered in more than one way (orally, anal suppository, injection, intravenous drip) with the safety and effectiveness of the drug differing in how it is to be administered. In many cases, drugs cannot be administered to a patient in the preferred way - for example, an unconscious person cannot swallow pills.
Although physicians can prescribe and administer pharmaceuticals, in most cases they are not allowed to dispense them. This is particularly true of controlled substances, such as narcotics, which must be carefully accounted for at each step of the supply change. Exceptions are made for pharmaceuticals used on an emergency basis, such as those used to treat severe allergies, tachycardia and bradycardia.