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Nursing 3703 Pharmacology in Nursing. Introduction to Drug Therapy Linda Self. Grouping of Drugs. Names may reflect the conditions for which they are used (e.g. antidepressants) May reflect their chemical characteristics (benzodiazepines)

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Nursing 3703 pharmacology in nursing

Nursing 3703Pharmacology in Nursing

Introduction to Drug Therapy

Linda Self

Grouping of drugs
Grouping of Drugs

  • Names may reflect the conditions for which they are used (e.g. antidepressants)

  • May reflect their chemical characteristics (benzodiazepines)

  • May reflect the effects on body systems (central nervous system depressants)

Prototype drugs
Prototype Drugs

  • Individual drugs that represent groups of drugs are called Prototypes

  • May be the first drugs of this group to be developed (e.g., penicillin for antibiotics, morphine for opioid analgesics)

Drug names
Drug Names

  • Generic Name is related to the chemical name and is independent of the manufacturer (e.g., sertraline)

  • Trade name is designated and patented by the manufacturer (e.g., Zoloft)

American drug laws and amendments
American Drug Laws and Amendments

  • 1938 Food, Drug and Cosmetic Act required proof of safety, authorized factory inspections, established penalties for fraudulent claims

  • 1952 Durham-Humphrey Amendment designated drugs that must be prescribed by a physician and dispensed by a pharmacist (e.g., controlled substances, etc.)

American drug laws cont
American Drug Laws cont.

  • 1970 Comprehensive Drug Abuse Prevention and Control Act; Title II, Controlled Substances Act

  • Categorized according to potential for abuse

  • Regulated distribution of narcotics and other drugs of abuse

  • DEA charged w/enforcing the Controlled Substances Act

Categories of controlled substances
Categories of Controlled Substances

  • Schedule I—not approved for medical use and have high abuse potentials; LSD, heroin, peyote, ecstasy (3,4 methyenedioxy-methamphetamine)

  • Schedule II—used medically. High abuse potential (methadone, meperidine, cocaine, pentobarbital, Tylox)

Categories of controlled substances continued
Categories of Controlled Substances continued

  • Schedule III-less potential for abuse than I and II but may lead to psychological or physical dependence (Vicodin, Tylenol with codeine)

  • Schedule IV-drugs have some potential for abuse (Valium, Dalmane, Klonopin)

  • Schedule V-contain moderate amounts of controlled substances. An example is Lomotil (atropine and diphenoxylate)

Pregnancy categories
Pregnancy Categories

  • Cat. A-studies in pregnant women failed to show risk to the fetus

  • Cat. B- animal studies have failed to show a risk to the fetus but there are no adequate studies in women

  • Cat. C-animal studies have shown an adverse effect on the fetus, no adequate human studies, benefits may outweigh risks

Pregnancy categories cont
Pregnancy Categories cont.

  • Cat. D-positive evidence of human fetal risk

  • Cat. X-animal or human studies have shown fetal abnormalities or toxicity


  • Involves drug movement through the body to reach sites of action, metabolism, and excretion

  • Specific processes are absorption, distribution, metabolism and excretion

Pharmacokinetics drug transport pathways
Pharmacokinetics-Drug Transport Pathways

  • Three main pathways of drug movement across cell membrances

  • Most common is direct penetration by lipid soluble drugs

  • 2nd pathway involves passage through protein channels. Gates open and close either by voltage gating or by assist of chemical substances (Na+ and K+ ions affecting some cardiac drugs)

Drug transport pathways cont
Drug Transport Pathways cont.

3. 3rd is by carrier proteins that transport molecules from one side of the cell membrane to the other. An example would be oral drugs that carry hormones to their sites of action

(see text for details)


  • Absorption-process that occurs from the time a drug enters the body to the time it enters the bloodstream to be circulated

  • Factors affecting absorption include: dosage form, route of administration, blood flow to the site of administration, gastrointestinal function, presence of food or other drugs

  • For many medications, food in the stomach slows absorption


  • Is the portion of a dose that reaches the systemic circulation and is available to act on body cells

  • IV administration is 100% bioavailable

  • Subcutaneous administrations has more rapid absorption than does the oral route

  • Mucous membranes allow for rapid and direct absorption into the bloodstream


  • Involves the transport of drug molecules within the body

  • After the drug is absorbed into the bloodstream, it is carried by the blood or tissue fluids to its sites of pharmacologic action, metabolism and excretion

  • Protein binding is an important factor in drug distribution

Distribution cont
Distribution cont.

  • Drug distribution into the CNS is limited because of the blood-brain barrier

  • Blood-brain barrier is composed of capillaries with tight walls which limits movement of drug molecules into brain tissue

  • Only drugs that are lipid soluble or have a transport system can cross the blood-brain barrier and reach therapeutic concentrations in brain tissue

Distribution cont1
Distribution cont.

  • Drug distribution during pregancy and lactation is unique as most drugs cross the placenta or in the case of lactation, pass into breastmilk

Protein binding
Protein binding

  • Most drugs form a compound with plasma proteins, mainly albumin, which act as carriers

  • Only the free or unbound portion of a drug acts on body cells

  • As unbound drug acts on cells, the decrease in plasma drug level causes some of the bound drug to be released

  • Protein binding allows a part of a drug dose to be stored and released as needed


  • Method by which drugs are inactivated or biotransformed by the body

  • Some drugs yield metabolites that are also active and exert effects on the body until they are excreted (normeperidine)

  • Most drugs are lipid soluble which aids their passage across the cell membrane

Metabolism cont
Metabolism cont.

  • Excretion usually is by kidneys. Need to be water soluble for this to occur. Thus, one function of metabolism is to convert fat soluble medications to water soluble ones.

  • Hepatic drug metabolism or clearance is a major mechanism for terminating drug action and eliminating drug molecules from the body

Metabolism cont1
Metabolism cont.

  • Most drugs are metabolized by the cytochrome P450 enzymes in the liver

  • Liver contains complex system of enzymes, three of which are key in the metabolism of medications/drugs

Cytochrome p450
Cytochrome p450

  • CYP enzymes catalyze the chemical reactions which ultimately metabolize the medications

  • With chronic administration (greater than 1-3 weeks), some drugs stimulate hepatocytes to produce larger amounts of drug metabolizing enzymes (inducers). Enzyme induction accelerates drug metabolism. Result is that larger doses of the drug may be need for therapeutic effects.

Cytochrome p4501
Cytochrome p450

  • Enzyme inhibition may occur with concurrent administration of two or more drugs that compete for the same metabolizing enzymes (e.g., Dilantin, EES, Tagamet)

  • Oral meds are generally absorbed by the GI tract and carried to the liver. Drug may undergo extensive metabolism leaving little for systemic use. This is called the first pass effect.


  • Refers to the elimination of a drug from the body

  • Most are excreted by the kidneys although some are excreted in the bile then the feces

Serum drug levels
Serum Drug Levels

  • Lab measurement of the amount of a drug in the blood at a particular time

  • Minimum effective concentration (MEC)-must be present before a drug exerts its pharmacologic action on body cells

  • Duration of action-time during which serum drug levels are at or above the MEC (may measure serum drug levels when the drugs have a low therapeutic index)

Pharmacodynamics receptors

  • Involves drug actions on target cells and the resulting alterations in cellular biochemical reactions

  • Most drugs chemically bind with receptors at the cellular level

  • Drug-receptor complex initiates physiochemical reactions that stimulate or inhibit cellular functions

Pharmacodynamics receptors1

  • Receptors vary in type, location, number and functional capacity

  • When drug molecules chemically bind with cell receptors, pharmacologic effects result from agonism or antagonism

Pharmacodynamics receptors2

  • Agonists-are drugs that produce effects similar to those produced by naturally occurring hormones, neurotransmitters and others. Agonists may accelerate or slow normal cellular processes depending on the type of receptor activated.

  • Antagonists—drugsthat inhibit cell function by occupying receptor sites.

  • Not all drugs act on receptors. Examples include: antacids, osmotic diuretics, chelators.

Variables that affect drug actions
Variables that affect drug actions

  • Dosage

  • Route

  • Drug-diet interactions. Food may slow absorption or foods may actually interact with certain medications (tyramine and MAO inhibitors; tetracycline and milk products; ingestion when taking certain antihypertensive medications)

Variables affecting drug actions
Variables affecting drug actions

  • Drug-drug interations-additive effects such as seen with sedatives and ethanol. Synergism as seen with acetaminophen and codeine.

  • Antidote—drug can be given to antagonize the toxic effects of another drug

Variables that affect drug actions1
Variables that affect drug actions

  • Age

  • Pregnancy

  • Body weight

  • Gender-hormonal effects

  • Pathologic conditions

  • Placebo response

Variables that affect drug actions2
Variables that affect drug actions

  • Genetics-hepatic drug metabolizing enzymes===acetyltransferase. Rapid acetylators may need larger than usual dosages and conversely, smaller doses if slow acetylators

  • Glucose-6-phosphate deficiency—develop hemolytic anemia if take antimalarials or sulfonamides

  • Ethnicity—ACE inhibitors in African Americans

  • Tolerance and cross tolerance

Adverse effects of drugs
Adverse effects of drugs

  • CNS

  • GI

  • Hematologic-anticonvulsants

  • Hepatic-acetaminophen, INH

  • Nephrotoxicity-aminoglycosides, NSAIDS

  • Hypersensitivity

  • Drug fever-fever associated w/administration of some antimicrobials, atropine or TCAs

Adverse drug effects
Adverse Drug Effects

  • Drug dependency

  • Idiosyncrasy

  • Carcinogenicity

  • teratogenicity

Toxicology drug overdosage
Toxicology—Drug Overdosage

  • General management

  • CPR

  • ETT

  • IV

  • Check blood sugar, drug screen, liver and kidney function

  • Charcoal

  • Narcan or possibly antidotes

  • May alkalinize the urine to prevent kidney damage

Antidotes for selected therapeutic drugs
Antidotes for Selected Therapeutic Drugs

  • Acetaminophen-mucomyst

  • Digoxin-digibind

  • Beta blockers-Glucagon (increases myocardial contractility)

  • Phenothiazines-benadryl (EPS)

  • Coumadin-vitamin K

  • Heparin-protamine sulfate

Antidotes cont
Antidotes cont.

  • Benzodiazepines—flumazenil

  • Cholinergics-atropine

  • Calcium channel blockers—calcium gluconate

General principles of accurate drug administration
General Principles of accurate drug administration

  • Six Rights

  • Right patient

  • Right drug

  • Right dose

  • Right route

  • Right time

  • Right documentation

General principles cont
General Principles cont.

  • Follow the ‘rights’ consistently

  • Learn essential information about each drug

  • Interpret prescriber’s orders correctly

  • Read labels for right medication and concentration

Drug administration
Drug Administration

  • Minimize the use of abbreviations

  • Calculate dosages correctly

  • Measure doses accurately

  • Use appropriate anatomic landmarks to identify sites of IM injections-follow manufacturers recommendations

  • Verify client identity

Drug administration1
Drug Administration

*****Seek information about the client’s medical diagnoses and condition in relation to drug administration

  • Be especially vigilant with children to avoid errors

Legal responsibilities
Legal Responsibilities

  • Nurse is legally responsible for safe and accurate administration of medications

  • Nurse is expected to have sufficient drug knowledge to recognize and question erroneous orders

  • Unit dose wrappings of oral drugs should be left in place until the nurse is in the presence of the client and ready to administer the medication

Medication orders
Medication Orders

  • Include the full name of the patient

  • Generic or trade name of the drug

  • The dose, the route and frequency of administration

  • Date, time and signature of the prescriber

Common abbreviations
Common abbreviations

  • PO

  • IM

  • IV

  • SL

  • Sub q

Times of drug administration
Times of Drug Administration

  • AC

  • Ad lib

  • bid, tid, qid

  • HS

  • PC

  • PRN

  • Stat

Drug dosages
Drug Dosages

  • cc

  • g

  • Gr

  • gtt

  • mL

  • oz

  • Tsp

  • tbsp

Routes of administration
Routes of Administration

  • Oral

  • Via GI tube

  • Parenteral-IM, IV and sub q

  • Topical

  • Rectal, ophthalmic

  • Otic

  • vaginal

Sites for injections
Sites for injections

  • Sub q-abdomen, thighs, back and upper arms

  • IM-deltoid, dorsogluteal, ventrogluteal and vastus lateralis muscles

  • IV-antecubital, hands, arms, external jugular

  • Others: intradermal, intra-articular, intra-arterial and intrathecal


  • Metric

  • Apothecary

  • Household

  • (see p. 37)

Drug administration cardinal rules
Drug administration cardinal rules

  • Wash hands before giving meds

  • Read MAR carefully. If ever in doubt, check the original order

  • Never give medications you are uncertain of unless you have looked them up or have consulted with pharmacy

Drug administration cardinal rules1
Drug Administration Cardinal Rules

  • Never give more than 3cc per IM injection

  • Wear gloves with all injections

  • For sub q injections, use 25G, 5/8” needles

  • Do not give oral meds if patient is vomiting, sedated, NPO or is unconscious

  • Follow narcotic protocol for signing out of narcotics

Nursing process in drug therapy
Nursing Process in Drug Therapy

  • Is a systematic way of gathering and using information to plan and provide individualized client care and to evaluate the outcomes of care

  • Five steps of the nursing process are: assessment, nursing diagnosis, planning, interventions and evaluation

General principles of drug therapy
General Principles of Drug Therapy

  • Expected benefits should outweigh potential adverse effects

  • Drug therapy should be individualized

  • Drug effects on quality of life should be considered in designing a drug therapy regiment

Drug selection and dosage
Drug selection and dosage

  • Use as few drugs as possible

  • Fixed dose combinations increase compliance

  • Lowest dose with therapeutic effect

  • Follow guidelines but dosages must be individualized

  • Drugs with long half-lives may require loading doses then titrated lower maintenance doses

Drug therapy in special populations pediatrics
Drug Therapy in special populations-pediatrics

  • Pediatrics-all aspects must be guided by the child’s age, weight and level of growth and development

  • Safe therapeutic ranges are less well-defined

  • Choice of drug is restricted because many drugs used in adults have not been sufficiently investigated

Pediatric physiologic characteristics affecting pharmacokinetics
Pediatric physiologic characteristics affecting pharmacokinetics

  • Thin, permeable skin –increased absorption of topicals

  • Immature blood-brain barrier—increased distribution into the CNS until age 2

  • Altered protein binding until age 1

  • Decreased activity of metabolizing enzymes in infants, increased in children

Pediatric physiologic effects
Pediatric physiologic effects pharmacokinetics

  • Increased percentage of body water

  • Decreased GFR until one year of age

Pediatrics pharmacokinetics

  • Oral route for meds is preferable

  • For injections, may wish to use EMLA (eutectic mixture of lidocaine and prilocaine, local anesthetics)

  • Site selection for injections—infants, use thigh muscles; older than 18 months of age, use deltoid; older than 3, use ventrogluteal muscle

Drug therapy in older adults physiologic characteristics and pharmacokinetic impact
Drug Therapy in Older Adults pharmacokineticsPhysiologic characteristics and pharmacokinetic impact

  • Decreased GI motility—slower absorption

  • Decreased cardiac output—slower absorption from site of administration, decreased distribution to sites of action in tissues

  • Decreased blood flow to liver and kidneys-delayed metabolism and excretion

Drug therapy in older adults
Drug Therapy in Older Adults pharmacokinetics

  • Decreased total body water and lean body mass-fat soluble meds stay with patient longer, water soluble drugs are distributed in smaller area, greater risk for toxicity

  • Decreased blood flow to liver-slowed metabolism and detox of drugs

Drug therapy in older adults1
Drug Therapy in Older Adults pharmacokinetics

  • Decreased albumin-decreased availability of protein for binding and transporting. Will also have higher concentration of free active drug.

  • Decreased blood flow to kidneys—impaired drug excretion, potential toxicity

Older adults renal impairment
Older Adults pharmacokineticsRenal Impairment

  • Know baseline renal function

  • Tailor dosages

  • Avoid nephrotoxic medications

  • Be aware of need for additional dosing if patient is receiving renal replacement therapy

Older adults hepatic impairment
Older Adults pharmacokineticsHepatic Impairment

  • Those with cirrhosis, hepatitis, receiving hepatotoxic drugs, have heart failure, are undergoing major surgery or have had trauma are at higher risk for toxicities r/t medications

  • Know drug effects on hepatic function

  • Reduce dosages on medications that are extensively metabolized by the liver such as: cimetidine, phenytoin, ranitidine, theophylline

Older adults critical illnesses
Older Adults pharmacokineticsCritical Illnesses

  • Be aware that all medications may have variable effects in this scenario

  • Know the actions, usual dosages and side effects of medications

  • Closely monitor renal and liver function tests

  • Monitor serum protein and albumin levels

Older adults critical illness
Older Adults pharmacokineticsCritical Illness

  • Most drugs will be given IV-for this reason, medications may have faster onset

  • Many factors may interfere with drug effects if given orally

  • Considerations when giving medications via feeding tube

  • Appropriate scheduling very important

Drug therapy in home care
Drug Therapy in Home Care pharmacokinetics

  • On patient’s turf

  • Schedule visit at convenient time for patient and caregiver

  • Assess patient’s ability to perform self-care

  • Assess patient’s understanding and attitude regarding medication regimen

  • Inquire if patient is taking any herbal preparations

Drug therapy in home care1
Drug Therapy in Home Care pharmacokinetics

  • Inquire if patient is taking any OTC meds

  • Assess environment for safety

  • Educate patient and caregiver indication, proper administration and side effects of administered medications

  • Between visits, maintain contact with patient to monitor progress and serve as a resource

Herbal and dietary supplements
Herbal and Dietary Supplements pharmacokinetics

  • Black cohosh-used to relieve menopausal s/s

  • Capsaicin-post-herpetic neuralgia

  • Echinacea-anti-infective, for common cold

  • Ginger—nausea. Not for morning sickness.

  • Garlic-cholesterol lowering

Herbal and dietary supplements1
Herbal and Dietary supplements pharmacokinetics

  • Feverfew-for migraines, menstrual complaints. Can cause withdrawal s/s.

  • Ginseng-increase stamina, endurance and mental acuity. Can affect bleeding time, BP, increase hypoglycemia. No longer than 3 weeks use with Siberian ginseng.

Questions pharmacokinetics