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Pharmacology

Rosalie C. Villora MSN, RN

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Objectives

• Identify principles of pharmacology that relate to nursing care.

• Explain absorption, excretion, desired effect.• Describe the 5 steps of the nursing process.• Explain how nursing process is used in the

administration of medications• Identify elements in a patient drug history• Identify common elements in a variety of hospital

medication records• Discuss charting do’s and don’ts• Discuss confidentiality issues as they apply to

medication administration

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Pharmacologic Principles• Pharmacology - study or science of drugs

• Pharmaceutics - study of how various drug forms influence pharmacokinetic and pharmacodynamic activities

• Pharmacokinetics - study of what the body does to the drugAbsorptionDistributionMetabolismExcretion

• Pharmacodynamics - study of what the drug does to the body, i.e. mechanism of drug actions in living tissues

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Pharmacologic Principles cont’d

• Pharmacotherapeutics - use of drugs and clinical indications for drugs to prevent and treat diseases– Empirical therapeutics – effective, but mechanism

of action is unknown– Rational therapeutics – specific evidence has

been obtained for the mechanisms of drug action

• Pharmacognosy - study of natural (plant and animal) drug sources

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Pharmacokinetics: Absorption

• The rate at which a drug leaves its site of administration, & the extent to which absorption occursBioavailability – measure

of the extent of drug absorption in the body (0% to 100%)

Bioequivalent – two drugs have the same bioavailability and same concentration of active ingredients

Factors That Affect Absorption

• Food or fluids administered with the drug

• Dosage formulation• Status of the absorptive

surface• Rate of blood flow to the

small intestine• Acidity of the stomach• Status of GI motility

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Neonatal and Pediatric Considerations: Pharmacokinetics

• AbsorptionGastric pH less

acidicGastric emptying is

slowed Intramuscular

absorption faster and irregular

• DistributionThe younger the

person, the greater the % of total body water

Greater TBW means fat content is lower

Decreased level of protein binding

Immature blood-brain barrier—more drugs enter the brain

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Neonatal and Pediatric Considerations: Pharmacokinetics

Metabolism

Liver immature, does not produce enough microsomal enzymes

Older children may have increased metabolism, requiring higher doses than infants

Excretion

Kidney immaturity affects glomerular filtration rate and tubular secretion

Decreased perfusion rate of the kidneys may reduce excretion of drugs

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The Elderly

Elderly: older than age 65Healthy People 2010:

older than age 55 Use of OTC medications Increased incidence of

chronic illnesses Polypharmacy -

“prescribing cascade”

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The Elderly: Pharmacokinetics

• AbsorptionGastric pH less acidicSlowed gastric

emptyingMovement through GI

tract slowerReduced blood flow to

the GI tractReduced absorptive

surface area due to flattened intestinal villi

• DistributionTBW percentages

lowerFat content increasedDecreased production

of proteins by the liver, resulting in decreased protein binding of drugs (& increased circulation of free drugs)

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The Elderly: Pharmacokinetics

MetabolismAging liver

produces fewer microsomal enzymes, affecting drug metabolism

Reduced blood flow to the liver

ExcretionDecreased

glomerular filtration rate

Decreased number of intact nephrons

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Pharmaceutics

• Dosage form design affects dissolution

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First-Pass Effect

• The metabolism of a drug and its passage from the liver into the circulation

– A drug given via the oral route may be extensively metabolized by the liver before reaching the systemic circulation (high first-pass effect)

– The same drug—given IV—bypasses the liver, preventing the first-pass effect from taking place, and more drug reaches the circulation

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Distribution

Protein-binding

Water soluble vs. fat soluble

Blood-brain barrier

Areas of rapid distribution: heart, liver, kidneys, brain

Areas of slow distribution: muscle, skin, fat

Metabolism (Biotransformation)

Liver (main organ) Skeletal muscle Kidneys Lungs Plasma Intestinal mucosa

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Factors that metabolism

• Fast acetylator• Barbiturate therapy• Rifampin therapy

Delayed drug metabolism results in:

• Accumulation of drugs

• Prolonged action of the drugs

Factors that metabolism

Cardiovascular dysfunction

Renal insufficiency Starvation Obstructive jaundice Slow acetylator Erythromycin or

ketoconazole drug therapy

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Excretion

The elimination of drugs from the body• Kidneys (main organ)

• Liver

• Bowel– Biliary excretion– Enterohepatic recirculation

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Half-life

• The time it takes for one half of the original amount of a drug in the body to be removed

• A measure of the rate at which drugs are removed from the body

• Most drugs are considered to be effectively removed after about five half-lives

• Steady state

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Onset, Peak, and DurationOnset• The time it takes for the drug to elicit a therapeutic

responsePeak• The time it takes for a drug to reach its maximum

therapeutic response • Highest blood levelTrough Level• Lowest blood levelDuration• The time a drug concentration is sufficient to elicit a

therapeutic response

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Pharmacodynamics: Mechanisms of Action

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Pharmacotherapeutics: Types of Therapies

• Acute therapy

• Maintenance therapy

• Supplemental/replacement therapy

• Palliative therapy

• Supportive therapy

• Prophylactic therapy

• Empiric therapy

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• Contraindication- any characteristic of the patient, especially a disease state, that makes the use of a given medication dangerous for the patient

• Intended therapeutic action (beneficial)

• Unintended but potential adverse effects (predictable, adverse reactions)

• Therapeutic index - ratio between a drug’s therapeutic benefits and its toxic effects

• Tolerance - a decreasing response to repeated drug doses

• Dependence - a physiologic or psychological need for a drug

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• Drug interactions: the alteration of action of a drug by other prescribed drugs, over-the-counter medications, & herbal therapies

• Drug interactionsAdditive effectSynergistic effectAntagonistic effectIncompatibility

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• Adverse drug reactions:Pharmacologic

reactions, including adverse effects

Hypersensitivity (allergic) reaction

Idiosyncratic reactionDrug interaction

Adverse effects Predictable, well-

known reactions that result in little or no change in patient management

Predictable frequency Occurrences are

related to the size of the dose

Usually resolve when the drug is discontinued

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Other Drug-Related Effects

• Teratogenic – results in structural defects in the fetus

• Mutagenic – permanent changes in the genetic composition and chromosome structure of living organism

• Carcinogenic – cancer-causing effects of drugs

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Pharmacology &

The Nursing Process

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The Nursing Process

• A research-based organizational framework for professional nursing practice

• Central to all nursing care

• Encompasses all steps taken by the nurse in caring for a patient

• Flexibility is important

• Critical thinking

• Ongoing and constantly evolving process

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The Nursing Process (cont’d)

• Assessment

• Nursing diagnosis

• Planning

• Goals

• Outcome criteria

• Implementation

• Evaluation

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The Nursing Process (cont’d)

Assessment• Data collection

– Subjective, objective• Medication history

– Prescriptions– OTCs– Herbals– Responses to medications (therapeutic &

adverse responses)

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The Nursing Process (cont’d)

Nursing diagnosis

• Decision about the need/problem (actual or at risk for) of the patient

• Critical thinking, creativity, and accurate data collection

• NANDA format

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The Nursing Process (cont’d)

Nursing diagnosis

Three steps• Human response

to illness (actual or risk)

• “related to”• “as evidenced by”

Planning• Identification of

goals and outcome criteria

• Time frame• Prioritization

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The Nursing Process (cont’d)

Goals

• S- specific• M- measurable• A- attainable• R- realistic• T- time frame

specified

Outcome Criteria

• Specific standard(s) of measurement

• Patient oriented

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The Nursing Process (cont’d)

Implementation• Initiation and completion of the

nursing care plan as defined by the nursing diagnoses and outcome criteria

• Follow the “Six Rights” of medication administration

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The Six Rights of Medication Administration

• Right drug

• Right dose

• Right time

• Right route

• Right patient

• Right documentation

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Other “Rights” (cont’d)

• Close consideration of special situations

• Prevention and reporting of medication errors

• Patient teaching

• Monitor therapeutic effects, adverse effects, and toxic effects

• Refusal of medication

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Six Elements of a Drug Order

1. Patient's name2. Date order is written3. Name of medication4. Dosage (size, frequency, &

number of doses)5. Route of delivery6. Signature of the prescriber

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Evaluation• Ongoing part of the nursing process• Determining the status of the goals and

outcomes of care• Monitoring the patient’s response to drug

therapy– Expected and unexpected responses