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Merck Manual

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Reading a Drug Label

Reading a Drug Label

Nonprescription drugs in the United States are required to have labels that explain what a drug’s benefits and risks are and how to use the drug correctly. The label is entitled “Drug Facts.” Active ingredients are listed at the top, followed by uses, warnings, directions, other information, and inactive ingredients.

Active ingredient: The drug itself is the active ingredient. Combination products have more than one active ingredient. The drug’s generic name is listed with the amount of drug in each tablet, capsule, or dose unit. The same generic drug may be sold under several different trade (brand) names.

Uses: Symptoms or disorders for which the drug product is recommended are listed.

Warnings: When the drug should not be used, when a doctor or pharmacist should be consulted (and after how long), and which factors can alter the expected response to the drug are listed, usually in four sections.

  • “Ask a doctor before use if you have” lists conditions that can make taking the drug more problematic or unsafe. This section refers to drug-disease interactions.

  • “Ask a doctor or a pharmacist before use if you are taking” lists other drugs that can interfere with the drug’s effectiveness or safety. This section refers to drug-drug interactions.

  • “When using this product” includes common side effects, foods that may interfere with the drug’s effectiveness or safety (drug-food interactions), and special precautions to take (for example, not driving while taking the drug).

  • The last section lists special warnings for women who are pregnant or breastfeeding and for children, with instructions about what to do in case of an overdose.

Directions: How much of the drug and how often to take the drug are given for different age groups, because size and age, among other factors, affect how a person responds to a drug.

Other information: Special instructions, such as how to store the drug so that it does not deteriorate, are listed.

Inactive ingredients: In addition to the drug, drug products—the tablets, capsules, or other formulations that consumers buy—contain substances added to facilitate the administration of the drug, such as ingredients that provide bulk or a pleasant taste and color. Products with the same active ingredient may contain different inactive ingredients. Inactive ingredients are usually harmless, but some of them cause an allergic reaction in a few people, who should look for products made without those ingredients.