Key Concepts, Chapter 29, Medications A drug or medication is any substance that modifies body functions when taken into the body. The study of drugs and their effect on the body’s functioning is called pharmacology. Drugs have several names, including generic and trade names. Drug preparations are available for oral, topical, and parenteral administration. Drug classifications, or drug classes, are groups of drugs that share similar characteristics. Knowledge related to the class of a drug can be applied to individual drugs in that class. Pharmacotherapeutics is the achievement of the desired therapeutic goal from drug therapy. It is the clinical purpose (the indication) for administering a drug. Understanding the desired outcome of administering a drug is an important part of nursing responsibilities related to medication administration. This knowledge is required to enable the nurse to assess the appropriateness of the medication, as well as provide appropriate and accurate patient education. Pharmacokinetics is the effect of the body on the drug, once the drug enters the body. It is the movement of drug molecules in the body in relation to the drug’s absorption, distribution, metabolism, and excretion. The process by which drugs alter cell physiology and affect the body is called pharmacodynamics. Undesirable effects other than the intended therapeutic effect of a drug are known as side effects; harmful or injurious effects are more serious and are frequently referred to as adverse drug reactions and may require official reporting. Certain variables can influence the action or effect of a medication. These variables include developmental considerations, patient’s body weight, patient’s biological sex, genetic and cultural factors, psychological factors, pathology, environment, and timing of medication administration. Blood levels of a drug are often measured to help evaluate whether a drug’s dose is at a level to achieve the desired effect and below the level at which adverse effects occur. Important legislation has influenced the administration of medication in the United States. Medication reconciliation, the process of specifying medications and maintaining a current, accurate list of medications the patient is receiving, has been shown to decrease the incidence of medication errors that occur during care at points of transition. There are several types of orders that a prescriber may write: a standing order (or routine order); a PRN order (“as needed”); the single, or one time, order; and a stat order. The medication order consists of seven parts: patient’s name, date and time the order is written, name of drug to be administered, dosage of the drug, route by which the drug is to be administered, administration frequency of the drug, and signature of the person writing the order. Medication orders require the drug, dose, rate, route, frequency, and, when appropriate, duration to be explicit and specific to the needs of the patient in order to achieve the desired outcome. Medications are supplied in a number of ways. Many facilities make use of one or more systems in conjunction with each other, or variations of systems. Nurses need to be proficient in the use of weights and measures as well as systems of measurement to calculate drug dosages and prepare medications for administration. Two systems of measurement are used in the United States for administering medications: the metric system and the household system. Several formulas can be used to calculate drug dosages: formula methods and dimensional analysis. Use of the three checks and the rights of medication administration when administering medications can assist with safe administration of medications. Controlled substances are secured at all times and have specific guidelines for administration and documentation. Positive identification of the patient is essential to safe drug administration. The nursing process can be applied to the administration of medications. Drugs given orally are intended for absorption in the stomach and small intestine. Certain solid dosage medications can be crushed. Medications can be administered via several parenteral routes: intradermal, subcutaneous, and intramuscular injections; intravenous bolus; and intermittent intravenous infusion. It is important to choose the right equipment to ensure correct administration via these routes. Injected medications also require knowledge of the correct angle of insertion and identification of appropriate landmarks to ensure accurate administration to the intended site. Medications delivered via the topical route are applied to the skin or mucous membranes, including the eyes, ears, nose, rectum, vagina, and lungs. The medication record is a legal document. Recording each dose of medication as soon as possible after it is given provides a documented record that can be consulted if there are any questions about whether the patient received the medication. The name of the medication, dosage, route of administration, time given, and name of the person administering the medication are noted in the record. Record the site used for an injection. Omitted or refused drugs require additional documentation. Prompt acknowledgment of medication errors may minimize their possible detrimental effect. Teaching about medications is a nursing responsibility and is an ongoing process. B or D • a Pharmacodynamics Pharmacodynamics is the process by which drugs alter cell physiology and affect the body. Drugs turn on, turn off, promote, or block responses that are part of the body’s processes. Drug–receptor interaction occurs when the drug interacts with one or more cellular structures to alter cell function. Drugs may also combine with other molecules in the body to achieve their effect. Other drugs act on the cell membrane or alter the cellular environment to achieve their effect. Pharmacokinetics (Effect of Body on Drug) Absorption First pass effect Factors affecting absorption of medications Distribution • Protein binding and solubility 9 Metabolism & Liver and cytochrome P-450 system @ Excretion D Kidneys r Drug Dose and Serum Drug Levels Therapeutic range: concentration of drug in the blood serum that produces the desired effect without causing toxicity • Route of administration Lipid solubility pH Blood flow Local conditions at the site of administration Drug dosage Adverse Drug Effects Allergic effects: anaphylactic reaction Drug tolerance : Toxic effect Idiosyncratic effect : Drug interactions: antagonistic and synergistic effects s C 0 Trough level: the point when the drug is at its lowest concentration, indicating the rate of elimination Half-life: amount of time it takes for 50% of blood concentration of a drug to be eliminated from the body Factors Affecting Drug Action Developmental considerations : Weight Gender : Genetic and cultural factors Psychological factors : Pathology Environment Timing of administration 8 A Types of Medication Orders Standing order (routine order): carried out until cancelled by another order PRN order: as needed Single or one-time order Stat order: carried out immediately Parts of the Medication Order Patient’s name Date and time order is written Name of drug to be administered Dosage of drug Route by which drug is to be administered Frequency of administration of the drug Signature of person writing the order Rights of Medication Administration Administration of Parenteral Medications Right medication Subcutaneous injection: subcutaneous tissue Right dosage Intradermal injection: corium(under epidermis) Right assessment data Right documentation Intra-arterial injection: artery Right patient Intramuscular injection: muscle tissue Right route Intravenous injection: vein Intracardial injection: heart tissue Intraperitoneal injection: peritoneal cavity Right response Intraspinal injection: spinal canal Right to education Intraosseous injection: bone Right to refuse Right time Criteria for Choosing Equipment for Injections Right reason Route of administration = Oral Medications Solid form: tablets, capsules, pills Liquid form: elixirs, spirits, suspensions, syrups Viscosity of the solution Quantity to be administered Body size Type of medication . Controlled Substances Required Information Name of patient receiving narcotic Amount of narcotic used Hour narcotic was given Name of physician prescribing narcotic Name of the nurse administering narcotic Administration of Oral Medications Oral route: having patient swallow drug Enteral route: administering drug through an enteral tube Sublingual administration: placing drug under tongue Buccal administration: placing drug between tongue and cheek
