This glossary serves as a clear, informative guide for common pharmacy and drug-related terms, to help you feel more confident in understanding your medications.

Navigating healthcare and medications often feels like learning a second language. From deciphering complex insurance jargon to understanding the specific clinical instructions on a pill bottle, the terminology can be overwhelming.

Learn more about your medications by understanding the following common terms that are often used in the world of pharmacy and prescriptions.

Active ingredient: What makes a drug work.

Adverse reaction: A harmful, unintended, and undesired response to a medication. Also referred to as “side effect”.

Abbreviations

The prescription you give to your pharmacist may have abbreviations on it. Your doctor may use these in the instructions for how to take the medication. Your pharmacist will translate these into plain language so you can clearly understand how to take your medication.

Read more: Learn about common abbreviations you may see on a prescription.

Biologics: A medication that is made from living cells. Because of this, they can’t be copied exactly like brand-name medications.

Biosimilars: A medication that is similar to a biologic drug (known as the reference drug).

Boxed warning: The most serious warning from the Food and Drug Administration (FDA) about drug effects that may be dangerous. A boxed warning is given to drugs that carry risks of severe adverse reactions that could lead to death or serious injury. Previously known as a “black box warning”.

Brand name: A medication that is made from chemicals that is given a trade name by the manufacturer. It is the original version of a medication that’s FDA-approved to treat a specific condition.

Contraindication: A factor or condition that could prevent your doctor from prescribing a drug due to the risk of harm.

Delayed-release: Describes a form of drug where the drug is released into your body after a time lag or it is released into your body after it passes through your stomach.

Extended-release: Describes a form of drug where the drug is slowly released into your body over a long period of time.

Food and Drug Administration (FDA): Organization responsible for protecting the public health and regulating the safety, efficacy, and security of human and veterinary drugs, biological products, and medical devices. It also ensures the safety of our food supply, cosmetics, and products that emit radiation. Additionally, the FDA regulates the manufacturing, marketing, and distribution of tobacco products.

Generic: A medication that is a copy of the active drug in a brand-name medication. A generic is considered just as safe and effective as the original drug but tends to cost less.

Half-life: Refers to the amount of time it takes the amount of drug in the body to reduce by half. It typically takes about 5 half-lives for a dose of a drug to be removed from the body.

Immediate-release: Describes a form drug where the drug is released into your body right away.

Indication: Another term for “use” of a drug. These are the conditions a drug has been approved to help treat or prevent.

Interaction: A change in the way a drug works in the body when it is taken with certain other drugs, foods, supplements, or herbs. A drug interaction may make a drug more or less effective or increase the risk of side effects from one or both of the drugs.

Intramuscular injection: An injection into your muscle.

Intravenous (IV) infusion: An injection given into your vein over time.

Mail order pharmacy: Pharmacy that provides home delivery for long-term maintenance drugs. These may be offered through the company that provides your prescription insurance. Some Medicare plans may help cover the cost of mail-order drugs

Mechanism of action: How a drug works in the body.

Pharmacodynamics: What the drug does to the body. This looks at how a drug interacts with a receptor, dose-response relationships, and mechanism of action.

Pharmacokinetics: What the body does to the drug. This looks at the absorption (how the drug gets into the bloodstream), distribution (how the drug moves from the bloodstream to the tissues), metabolism (how the drug is broken down in the body), and excretion (how the drug is removed from the body).

Prescribing information: Detailed information about a drug, including it’s uses, dosage, warnings, and mechanism of action, that is drafted by the manufacturer and approved by the FDA. It may also be called product information, product labeling, or the package insert.

Prior authorization: Your insurance company may require prior authorization before it covers your medication. This means the company and your doctor will discuss the drug in regard to your treatment. The insurance company will then determine whether that medication is covered.

Specialty pharmacy: A pharmacy that is authorized to handle drugs that need special handling, storage, and administration. These drugs typically treat rare and complex medical conditions like cancer, rheumatoid arthritis, and multiple sclerosis. This type of drug may be costly or require help from healthcare professionals to be taken safely and effectively.

Subcutaneous injection: An injection given under the skin.

Terminology in healthcare can feel overwhelming. If you ever have questions about what a term means, be sure to talk with your doctor or pharmacist for more information.

Disclaimer: While Healthline strives for factual, comprehensive, and current information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.