Pharmacology and the Nursing Process

Pharmacology principles

Name, classification, pharmacokinetics, medication response

Drug naming process

Generic name, trade/brand name, chemical name

Generic name (nonproprietary name)

Name given by the United States Adopted Names Council

Trade/brand name (proprietary name)

Drug has a registered trademark, use of name restricted by drug’s patent owner

Drug classification

Drug class → grouped together based on similar properties → commonly classified by therapeutic use → subclasses

Pharmacokinetics

What the body does to the drug; absorption, distribution, metabolism, excretion

Absorption

Transmission of medications from location of administration (oral, muscle, skin, mucous membranes, subcutaneous tissue) to the bloodstream

Distribution

Delivery to intended tissue

Metabolism

How drug is broken down, changes drugs into less active or inactive forms by action of enzymes, usually happens in liver

Excretion

Removing drug from body, primarily kidney’s responsibility, bowel also plays role, kidney dysfunction can lead to an increase in duration and intensity of a medication response

Bioavailability

How much of the drug is absorbed, oral meds have <100%

First pass effect

Drug from GI tract (enteral) much less available because liver destroys it before entering circulation

Pharmaceutics

How drug form influences the speed in which the drug is absorbed by the body

Factors altering absorption of oral drugs

Gastric ph and emptying time, presence of food in the stomach, forms of meds (enteric coating or sustained release), other medications

Factors influencing distribution

Circulation, plasma protein binding

Circulation

Conditions that inhibit perfusion (vascular or cv disease) can delay distribution

Plasma protein binding

Drugs compete for protein binding sites within the bloodstream (albumin), ability to bind to a protein can affect how much of the drug will travel to the target site, drugs can compete for the same binding sites (toxicity)

Distribution affecting factors

Low albumin levels, taking multiple medications at same time that are highly protein bound (Drug-Drug Interaction)

Factors influencing rate of metabolism

Age, higher level of drug-metabolizing enzymes (genetics), similar metabolic pathways (drug-drug interaction), leads to slowing metabolism, nutritional status

Outcomes of metabolism

Increased excretion, unactivation of medications, increased therapeutic effect, activation of pro-drugs into active form

Medication responses

Medication dosage attempts to maintain plasma levels between minimum effective concentration and toxic concentration, therapeutic index + therapeutic levels (peak and trough), half-life, pharmacodynamics

Peak level

Max concentration of drug in body after administration. (30 minutes after IV, 1 hour after PO)

Trough level

Lowest concentration in body after fall from peak level. (measured immediately before next

dose)

Half-life

Time for the medication in the body to drop by 50%, takes 4 half-lives to achieve a steady blood concentration, considered eliminated (no longer exerting effect) after 5 half lives, liver and kidney function affect half-life

Short half-life

Medications leave the body quickly (4-8 hrs), short dosing intervals (q4 hrs)

Long half-life

Medications leave the body slowly, greater risk for accumulation and toxicity, meds can be given at longer intervals, but take longer to reach a steady state

Pharmacodynamics

Interactions between medications and target cells to produce effects

Mechanisms of action

Acting on receptors (Agonist, Antagonist, Partial), blocking or stimulating enzymes, altering ion channels, affecting transporters or pumps, replacing missing substances, direct physical or chemical action

Uncontrolled substances

Do not generally pose risks of misuse and addiction

Controlled substances

Have a potential for misuse and dependence, have a “schedule” classification; schedule I has no medical use in the US

Medication prescriptions

Most often written (usually electronically through EMR), use verbal prescriptions only for emergencies, and follow facility’s protocol for telephone prescriptions, nursing students cannot accept verbal or telephone prescriptions

Types of medication prescriptions

Routine, single or one-time, stat, PRN

Components of medication prescription

Patient Name and medical record number, date and time order was written, generic drug name, dosage, route of administration, frequency of dosing, prescriber signatur

Medication reconciliation

TJC requires policies and procedures; list of current medications, including med name, dosage, frequency, is compiled; nurses compare list with new medication prescriptions and reconcile it with provider to resolve discrepancies; takes place upon admission, transferring to another unit or facility, at discharge

Medication rights

Right patient, drug, dose, time, indiction, route, response, documentation, education

Common medication errors

Wrong medication or IV fluid, incorrect dose or IV rate, wrong client, route, or time, administration of allergy-inducing medication, omission of a dose or administration of an extra dose, incorrect discontinuation of a medication or IV fluid, inaccurate prescribing, inadvertently giving a medication with a similar name

Bar code scanning

Leads to safer practice/less medication errors, integrated in almost every setting (esp. acute care), expected standard of practice, supports documentation of administration

Drugs commonly involved in severe medication errors

Insulins, anticoagulants, opioids, chemotherapeutic drugs

Committing a medication error

Ensure patient safety first, notify appropriate people, monitor and intervene, document objectively, learn from error