DRUG ACTION: PHARMACEUTIC,

PHARMACOKINETIC, AND PHARMACODYNAMIC

PHASES

Differentiate the 3 phases of drug actionIdentify the 2 processes that occur before

tablets are absorbed into the bodyDescribe the 4 processes of pharmacokineticsExplain the meaning of pharmacodynamics,

dose response, maximal efficicy, the receptor, and, nonreceptor to drug action

Define the terms protein-bound drugs, half-life, therapeutic index, therapeutic drug range, side effects, adverse rxns, and drug toxicity

Describe the nursing implications of pharmacokinetics and pharmacodynamics

PharmaceuticDisintegration and dissolution

Rate limiting

The two pharmaceutic phases are disintegration and dissolution.

AbsorptionProcesses of drug absorption

The three major processes for drug absorption through the gastrointestinal membrane are passive absorption, active absorption, and

pinocytosis.

AbsorptionWater-soluble vs. lipid-soluble drugsFirst-pass effectBioavailability

Some factors affect rate of drug absorption

Distribution Protein-bindingFree drugsVolume of drug distribution (Vd)

Drug distribution.

Metabolism (biotransformation)Half-life (t½); see Table 1-2

Excretion (elimination)Kidneys

Creatinine clearanceLiverFeces, others

What happens when there is slow rate of drug excretion?

Dose response and maximal efficacyOnset, peak, and duration of action

The time-response curve evaluates three parameters of drug action: (1) onset, (2) peak, and

(3) duration. MEC, Minimum effective concentration; MTC, minimum toxic concentration.

Receptor theoryAgonists vs. antagonists

Two drug agonists attach to the receptor site. The drug agonist that has an exact fit is a strong agonist and is more biologically

active than the weak agonist.

Nonspecific drug effect

Cholinergic receptors are located in the bladder, heart, blood vessels, stomach, bronchi, and eyes.

Nonselective drug effect

Epinephrine affects three different receptors: alpha, beta1, and beta2.

Categories of drug actionStimulation or depressionReplacementInhibition or killing of organismsIrritation

The therapeutic index measures the margin of safety of a drug. It is a ratio that

measures the effective therapeutic dose and the lethal dose.

A, A low therapeutic index drug has a narrow margin of safety, and the drug effect should be closely monitored. B, A high

therapeutic index drug has a wide margin of safety and carries less

risk of drug toxicity.

Therapeutic range (therapeutic window)Peak and trough levels; see Table 1-4Loading doseSide effects, adverse reactions, and

toxic effectPharmacogeneticsTachyphylaxisPlacebo effect

The three phases of drug action.

AssessmentNursing interventionsCultural considerationsEvaluation

Determinants that affect drug therapy.

TC has liver and kidney disease. He is given a medication with a half-life of 30 hours. You expect the duration of this medication to:

A. increase.B. decrease.C. remain unchanged.D. dissipate.

Answer: A

In older adults and those with renal dysfunction, the creatinine clearance is usually:

A. substantially increased. B. slightly increased.C. decreased.D. in the normal range.

Answer: C