A drug is any substance that can modify one or more of the body’s functions. A medication is a chemical substance intended for use in the diagnosis, treatment, cure, mitigation, or prevention of a disease. Nurses are responsible for administering drugs and for teaching clients how to administer their own medications. Nurses need to understand the principles of pharmacology as well as the safe administration of medications. The United States Food and Drug Administration (FDA) regulates the manufacture, sale, and effectiveness of medications. United States narcotics laws have delegated the use of narcotics and other controlled drugs to the Drug Enforcement Administration (DEA).

Each state’s Nurse Practice Act outlines the scope of nursing practice, including the nurse’s responsibilities in giving medications. Medications are identified by chemical, generic, or trade names. The chemical name is the exact description of the drug’s composition. The generic name is the drug name assigned by the United States Adopted Names Council to the first manufacturer of the drug. The trade (brand or proprietary) name is the name the company uses to market the medication. Nurses should consult a drug reference guide or formulary to check the names and spellings of medications they give. Medications are classified by the body system with which they interact (e.g., cardiovascular) or by the condition they treat (e.g., antihypertensives).

Pharmacokinetics is the study of the absorption, distribution, metabolism, and excretion of drugs to determine the relationship between the dose of a drug and the drug’s concentration in biological fluids. Absorption of medication depends on the drug’s physiochemical effects, dosage, route of administration, and interaction with other substances in the digestive system, as well as on client characteristics, such as age. The more rapid the rate of dissolution (rate at which a drug becomes a solution) of a drug, the more quickly it can be absorbed. Liquid medications absorb more readily than tablets. A rich blood flow to an absorption site facilitates absorption. Therefore, sublingual medications are absorbed more quickly than medications that are injected into the subcutaneous tissue. Medications that are injected intramuscularly into a person in shock (when blood supply is shunted to the core of the body) are poorly absorbed. Acidic medications are absorbed better in the acidic environment in the stomach, while alkaline medications are absorbed better in the alkaline environment of the small intestine. Some oral medications are poorly absorbed when taken with food and others interact with each other to impair absorption. Sustained release medications are coated so the medication is released slowly.

Distribution is the movement of medications from the blood into various body fluids and tissues. Distribution is affected by blood flow, cell membrane permeability, the protein-binding capacity of the medication, and the client’s body composition. A high proportion of body fat slows the distribution of medications. Metabolism (biotransformation) occurs primarily in the liver and results in the deactivation of medications. Metabolism is slowed when the client has cirrhosis of the liver and enhanced when the client has a fever. Excretion is the elimination of medications from the body from the liver/biliary system, kidneys, sweat glands, skin, breast glands, and tear ducts. Excretion is most commonly affected by kidney disease.

A medication’s half-life is the time it takes the body to eliminate half of the blood level of a drug dose. Half-life is roughly correlated with duration of action. Several terms are used to describe drug action: onset, peak plasma level, trough, duration, and plateau. Onset of action is the time it takes the body to respond to a drug after administration. The peak plasma level is the highest blood concentration of a single drug dose before the elimination rate equals the rate of absorption. Trough, measured immediately before a scheduled dose, is the lowest blood serum concentration of a drug in a person’s system. Duration is the time a drug remains in the system in a concentration great enough to have a therapeutic effect. Plateau is the blood concentration level maintained after a series of scheduled drug doses is administered. The therapeutic range of a medication is the range of drug concentration in the blood that gives the desired effect without causing serious side effects or toxicity.

Adverse actions of drugs include side effects, adverse reactions, toxic effects, drug allergies, and idiosyncratic reactions. Side effects are possible harmful actions of a medication. An adverse reaction is an unexpected, harmful outcome of taking a medication. A toxic effect is an accumulation of a drug in the blood. A drug allergy is an antigen-antibody immune reaction occurring when an individual has developed antibodies against a drug.

Sometimes medications affect each other when taken at the same time. Medications can potentiate each other or interfere with the absorption of another drug. Food can likewise interfere with absorption or action of medications. Most interaction problems occur with the use of diuretics, oral antibiotics, anticoagulant drugs, and antihypertensive drugs. Client characteristics, such as genetic factors, gender, age, height, weight, physical conditions, and mental conditions, also affect the pharmacokinetics of a drug.

Drugs are available in many forms for administration by the route by which they are absorbed: oral, buccal, sublingual, rectal, parenteral, otic, vaginal, topical, inhalation, or intraocular. The rates by which medications are absorbed vary by route. The effects of medication may be local (on the cellular or organ level), systemic, or both local and systemic.

Most medications are given orally. Oral drugs are contraindicated in people with gastrointestinal disturbances or clients who can take nothing by mouth (NPO). They are given cautiously to people with swallowing disorders. Oral administration includes administration through gastric or intestinal tubes. The nurse should check the tube for patency, placement, and residue (gastric contents) before administering a medication. Medications that would be destroyed in the stomach or small intestines are given sublingually or buccally so they can be absorbed in the mouth.

The most common parenteral routes include intradermal (ID, injected into the dermis), subcutaneous (SC or SQ, injected into the subcutaneous tissue), intramuscular (IM, injected into the muscle), and intravenous (IV, injected into a vein). Topical medications are given to deliver a drug (1) for local effect on the skin or mucous membrane or (2) for systemic effect by absorption into the circulatory system.

There are several types of medication orders. A stat order is an order for a single dose of medication to be given immediately. A standing (scheduled) order is administered routinely as specified until it is canceled by another order. Certain medications, such as antibiotics, are discontinued after a set time according to institutional policies. A prn order is an order for a drug to be administered as needed. A medication order should include the name of the client, the date and time when the order is written, the name of the drug to be administered, the dosage, the route, the time of administration and frequency, and the signature of the person writing the order. Dosages may be given using metric, apothecary, or household measurements. Each agency has a list of abbreviations approved for medication orders. Only approved abbreviations may be used for medication ordering and documentation in that agency.

A nurse may need to do a drug dose calculation when administering medications. The most common method used is a ratio formula based on dosage on hand and the dosage required. Several “rules” are used to calculate infant and child dosages, based on body surface area, weight, and the age of the child. Health care agencies require nurses to count narcotics and controlled substances periodically to control drug misuse. Nurses who are drug abusers were formerly punished by the state in which they practiced. Currently, programs for impaired nurses focus on helping rather than punishing.

Safe medication administration depends on the clarity of the order and the nurse’s knowledge about the actions of medications. The nurse should clarify any sources of error, such as misspellings, unclear handwriting, or unclear verbal orders, with the prescriber of the medication. Nurses have traditionally used the “five rights” as a guideline to medication administration: right medication, right dose, right client, right route, and right time and frequency. Nurses use the Medicine Administration Record (MAR) to list medications to be given.

When administering a medication, the nurse checks the medication label when removing the medication from the storage area, the medication label against the MAR, and the medication label and MAR with the client’s name band at the bedside. The nurse should never administer medications that have been set up by another nurse or ignore clients’ questions about their medications. When calculating medication doses, especially insulin doses, the nurse should double check calculations with another nurse before administering. Nurses should always use a pill cutter for accuracy when cutting pills in half, and should only halve pills that are scored. Nurses should document medication given immediately after it is given. If the client does not take the medication, the nurse should circle the dose not given and document why is was not given on the client’s record.

Medication errors include violations of the “five rights,” giving the wrong medication; giving a medication to the wrong client; and using the wrong dose, frequency, or route. Mistakes can include inaccurate drug calculations, errors in writing or transcribing orders, drug omissions, late drugs, and mistakes from sound-alike or look-alike medication names. Nurses should document medication errors on an incident report and notify the prescribing practitioner immediately. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) currently requires organization-wide systems for handling medication errors and other safety issues.

The nursing process applied to medication administration includes an assessment of the client’s health history, such as preexisting conditions; lactation status; current medications, including prescribed medications, herbal remedies, supplements, and over-the-counter drugs; and drug allergies. Any medications brought to the nursing facility should be returned to the family for disposal. The nurse should also asses the client’s biological, psychological, social, and cultural status. Possible nursing diagnoses related to medication administration are Deficient Knowledge, Ineffective Therapeutic Regimen Management, Ineffective Health Maintenance, Impaired Physical Mobility, Disturbed Sensory Perception, and Impaired Swallowing.

Planning involves withholding medication until certain laboratory tests are performed and allowing enough time for client teaching. The nurse develops goals based on nursing diagnoses. Client teaching is a major goal in relationship to medication administration. Clients should be able to adhere to a medication schedule, self-monitor for side effects, and understand the importance of checking with the prescriber before taking over-the-counter or herbal preparations. Some conditions, such as diabetes mellitus, require extensive client teaching. Nurses are also responsible for evaluating the client’s responses to medications, level of knowledge and skill, and adherence to the medication regimen, being alert to factors that may affect adherence, such as financial resources or transportation.