Pharmacology Introduction Definitions › Pharmacology: – The science of drugs, their composition, uses, and effects, the characteristics or properties of a drug *Nurses need to have knowledge about the actions and effects of medications *To safely and accurately administer medications, nurses need to have an understanding of pharmacologic principles Drug Names › Chemical name – Describes the drug’s chemical composition and molecular structure › Generic name (nonproprietary name) – Name given by the United States Adopted Name Council › Trade name (proprietary name) – The drug has a registered trademark; use of the name restricted by the drug’s patent owner (usually the manufacturer) Drug Names **Nurses need to know both names, but should use the generic name (May be more than one trade name, NCLEX uses generic name) Example: Pharmacological Concepts: Classification › Classification- Nurses learn to categorize meds with similar characteristics by their class by: Usage – why the drug is used Body system – where the drug works Chemical or pharmacological class – what the drug is made of Pharmacological Concepts: Classification › Medication classification indicates the effect of the med on the body system, the symptom the med relieves, or the med’s desired effect (e.g. oral hypoglycemic, beta-blockers) › A medication may also be part of more than one classification system Example: Aspirin is an analgesic, antipyretic, anti-inflammatory, and anti-platelet agent Pharmacological Concepts: Classification When in doubt, look it up! As a nurse, you are professionally, ethically, legally, and personally responsible for every dose of medication you administer. Pharmacokinetics › The processes of drug absorption, drug distribution, drug metabolism, and drug excretion –Absorption –Distribution –Metabolism –Excretion ***It’s important to understand the difference between: Pharmacokinetics-drug movement Pharmacodynamics-drug action Routes of Medication Administration › Drugs are manufactured for a specific route of administration and are absorbed at different rates depending on the route of administration. › Routes of administration Oral- the drug is swallowed and absorbed from the stomach or small intestine Enteral- drug is given directly to the stomach or intestine Sublingual – the drug is held under the tongue and absorbed through the mucosa Buccal/Transmucosal – medication is held against the mucous membrane of the cheek until it dissolves Routes of Medication Administration cont’d Topical (skin) – drug acts locally and is absorbed though the skin Topical (Instillations) - The drug is placed into a body cavity (e.g., urinary bladder, rectum, vagina, ears, nose, eye) Topical (Inhalation) - A device (e.g., nebulizer, face mask) **Some drugs are intended for local effects in the respiratory passages; others (e.g., anesthetic gases) are for systemic effects, especially in the brain Parenteral - drug taken into the body other than through the digestive system Intravenous – medication directly to the vein – circulatory system Intramuscular Subcutaneous Forms of Medications › Medications are available in a variety of forms and preparations › The form of the med will determine its route of administration › Composition of med is designed to enhance its absorption & metabolism › Many meds are available in several forms › Tablet › Capsule › Elixir › Enteric-coated › Suppository › Suspension › Parenteral › Transdermal patch Oral Medications Advantages Convenient Sterility is not needed Economical Noninvasive, low-risk procedure Easy to administer, good for self-administration Capsule can mask unpleasant taste Capsule can be time released Disadvantages Unpleasant taste may cause non-compliance May irritate the stomach Patient must be conscious Digestive juices may destroy drug Cannot use if the patient have difficulty swallowing May be harmful to teeth How are drugs metabolized in the body? › Metabolism (or biotransformation) –is the chemical inactivation of a drug through its conversion into a more water-soluble compound or into metabolites that can be excreted from the body –Once a medication reaches its site of action, it is metabolized (changed into the inactive form) in preparation for excretion **Metabolism takes place in the liver Why is it important to know that? How Are Drugs Excreted From the Body? › Kidneys - are the primary site of excretion › Liver and GI Tract - some drugs broken down by the liver are excreted into the GI tract and eliminated in the feces › Lungs – drugs are removed through exhalation › Exocrine Glands - excretion through the exocrine (sweat and salivary) glands is limited Definitions, Cont’d… › Biological Half-Life: – The time required for half the quantity of a drug or other substance deposited in a living organism to be metabolized or eliminated by normal biological processes –the time required for something to fall to half its original value Example: Tramadol a narcotic-like pain reliever, has a half-life of approximately 6 hours. This means if you take a 50-mg dose at 0800, by 1400 half of that dose (25 mg) will still be left in your body. In 12 hours, one-fourth of the initial dose (12.5 mg) will be left in your body Onset, Peak, Duration › Onset – The time it takes for the drug to elicit a therapeutic response › Peak – The time it takes for a drug to reach its maximum therapeutic response › Duration – The time a drug concentration is sufficient to elicit a therapeutic response FIGURE 26-4 Pharmacodynamics: The study of actions and/or effects of the drug in living organisms › Drug-induced alterations to normal physiologic function › Positive change: – Therapeutic effect or goal of therapy › Negative change: – Side effects – Adverse effects Pharmacodynamics › Mechanism of Action › Therapeutic Effect › Side Effects › Adverse Effects › Toxic Effect › Idiosyncratic Reactions › Allergic Reaction › Medication Interactions › Iatrogenic Response Mechanism of Action › In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect › A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an enzyme or receptor › Example: Furosemide MOA – Furosemide works by blocking the absorption of sodium, chloride, and water from the filtered fluid in the kidney tubules, causing a profound increase in the output of urine (diuresis) Therapeutic Effect › The expected or predictable physiological response a medication causes › A single med can have several therapeutic effects (Aspirin) › It is important for the nurse to know why med is being prescribed – What do we want to happen? – What do we expect to see? – How will we know it worked? › Not just recognizing the action but seeing evidence of the goal › Furosemide will relieve symptoms of CHF through its action, and we will see this therapeutic effect in decreased respiratory difficulty (rate and effort) and reduction of pulmonary crackles Side Effects › Unintended secondary effects a medication predictably will cause › May be harmless or serious › If side effects are serious enough to negate the beneficial effect of meds therapeutic action, it may be dicontinued › People may stop taking medications because of the side effects › Furosemide SE: frequent urination, hypokalemia, hypovolemia, hypotension Adverse Effects › Undesirable response of a medication › Unexpected effects of drug not related to therapeutic effect › Should be reported to FDA – file an Adverse Drug Reaction (ADR) report › Can be a side effect or a harmful effect › Can be categorized as pharmacologic, idiosyncratic, hypersensitivity, or drug interaction › Furosemide can lead to hearing loss, erythema multiforme major (Steven Johnson Syndrome) Steven-Johnson Syndrome › Black Box Warning: – A warning that appears in the instructions for use surrounded by a thick black box to alert medical professionals to serious life-threatening adverse effects associated with the drug’s usage. › Toxic effect may develop after prolonged intake or when a med accumulates in the blood because of impaired metabolism or excretion, or excessive amount taken – Toxic levels of opioids can cause respiratory depression – Antidotes available to reverse effects › Allergic reaction – Unpredictable response to a medication – Makes up greater than 10% of all medication reactions – Client may become sensitized immunologically to the initial dose, repeated administration causes an allergic response to the med, chemical preservative or a metabolite Allergic Reaction › Medication acts as an antigen triggering the release of the body’s antibodies – May be mild or severe › Among the different classes of meds, antibiotics and opiates cause the highest incidence of allergic reaction › Anaphylaxis › Drug rash › Etc. Other Drug Reactions: Definitions › Teratogenic-Structural effect in unborn fetus (thalidomide) › Carcinogenic-Causes cancer › Drug interactions-occurs when one med modifies the action of another – Common in people taking several medications at once – One med may potentiate or diminish the action of another or alter the way it is absorbed, metabolized or eliminated – Warfarin and Amiodarone Other Drug Reactions: Definitions › Idiosyncratic Reactions - is an unexpected, abnormal, or peculiar response to a medication. It may take the form of the following responses to a drug: Extreme sensitivity Lack of response A paradoxical (opposite of expected) response, such as agitation in response to a sedative › Iatrogenic-unintentional adverse effects that occur during therapy – Treatment-Induced Dermatologic-rash, hives, acne – Renal Damage-Aminoglycoside antibiotics, NSAIDS, contrast medium – Blood Dyscrasias- Destruction of blood cells (Chemotherapy) – Hepatic Toxicity-Elevated liver enzymes (hepatitis-like symptoms) › Synergistic-Effect of 2 meds combined is greater than the meds given separately – Alcohol & Antihistamines, antidepressants, barbiturates, narcotics – Not always undesirable, physician may combine meds to create an interaction that will have beneficial effects (Vasodilators & diuretics to control high BP) › Incompatibility: › Undesirable interaction between drugs not suited to be administered together › Drug Tolerance: –Requirement of larger doses to be consumed in order to obtain desired effects; decreased drug effect occurring after repeated drug administration › Drug Resistance: – Lack of responsiveness to administered medication › Drug Tolerance: –Ability of the body to alter its response (adapt) to drug effects so that effects are minimized over time more drugs are needed to achieve the same therapeutic level › Drug Resistance: – Lack of responsiveness to administered medication › Incompatibility: – Undesirable interaction between drugs not suited to be administered together Definitions, Cont’d… › Loading Dose: – Initial drug dose administered to achieve rapid therapeutic drug concentrations › Maintenance Dose: – dose needed to maintain therapeutic blood levels; maintain blood levels in the therapeutic range › Polypharmacy: – situation where patients are taking multiple medications for the same condition › Often prescribed by different specialist › Common in the elderly Rights of Medication Administration 1. Right Patient 2. Right Medication 3. Right Dose 4. Right Route 5. Right Time 6. Right Documentation Medication Rights Right patient – Check the name on the order and the patient. Use 2 identifiers. Ask patient to identify himself/herself – When available, use technology (for example, bar-code system) Right medication – Check the medication label. Check the order Right dose – Confirm the appropriateness of the dose using a current drug reference – If necessary, calculate the dose and have another nurse calculate the dose as well Medication Rights Right route – Again, check the order and appropriateness of the route ordered – Confirm that the patient can take or receive the medication by the ordered route Right time – Check the frequency of the ordered medication – Double-check that you are giving the ordered dose at the correct time – Confirm when the last dose was given Medication Rights Right documentation – Document administration AFTER giving the ordered medication – Chart the time, route, and any other specific information as necessary. For example, the site of an injection or any laboratory value or vital sign that needed to be checked before giving the drug. Other “Rights” Right reason – Confirm the rationale for the ordered medication. What is the patient’s history? Why is he/she taking this medication? – Revisit the reasons for long-term medication use Right response – Make sure that the drug leads to the desired effect. If an antihypertensive was given, has his/her blood pressure improved? Does the patient verbalize improvement in depression while on an antidepressant? – Be sure to document your monitoring of the patient and any other nursing interventions that are applicable Other “Rights” › System Analysis – The entire system of medication management needs a constant “double-check” – Ordering, dispensing, preparing, administering, documenting – Involves the physician, nurse, nursing unit, pharmacy department, and patient education › Close consideration of special situations › Prevention and reporting of medication errors › Refusal of medication › Patient teaching Patient Safety Preventing Medication Errors › Minimize verbal or telephone orders – Readback and verify › Avoid medical shorthand, including abbreviations and acronyms – Abbreviation – “Do not use list” Preventing Medication Errors › Never assume anything about items not specified in a drug order (i.e., route) › NEVER use “trailing zeros” with medication orders – Do not use 1.0 mg; use 1 mg. 1.0 mg could be misread as 10 mg, resulting in a tenfold dose increase › ALWAYS use a “leading zero” for decimal dosages › Do not use .25 mg; use 0.25 mg – .25 mg may be misread as 25 mg. “.25” is sometimes called a “naked decimal”
