Chapter 2
Pharmacological Principles Part 2
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Pharmacokinetics (cont.)
Half-life: time required for half (50%) of a given
drug to be removed from the body during
elimination phase
Ø Steady state: amount of drug removed via
elimination = amount absorbed with each dose;
takes about 4-5 half lives of drug administration
• Steady state means consistent blood levels and
Ø
correlates with maximum therapeutic benefits
Onset of action
Ø Peak effect
Ø Duration of action
Ø
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Pharmacokinetics (cont.)
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The length of time until
the onset and peak of
action and the duration of
action play an important
part in determining the
peak level (highest blood
level) and trough level
(lowest blood level) of a
drug. If the peak blood
level is too high, then
drug toxicity may occur.
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Pharmacokinetics (cont.)
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Peak level: highest blood level of a drug
Trough level: lowest blood level of a drug
Toxicity: occurs if the peak blood level of the drug is
too high
Therapeutic drug monitoring – used to monitor
peak/trough, adequate therapeutic effects, minimize
drug toxicity
Note: Know your onset, peak and duration of
action of drugs
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Pharmacodynamics
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The study of what the drug does to the body
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The mechanism of drug actions in living tissues
Therapeutic effect – a positive effect on faulty
physiology. The goal of drug therapy.
Mechanism of action – modified cell or tissue
function
Receptor interactions – drug/receptor binding
Enzyme interactions – drug/enzyme binding
Nonselective interactions – disrupt cell process in
various ways
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Pharmacodynamics (cont.)
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Pharmacotherapeutics
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The clinical use of drugs to prevent and treat
diseases
Desired therapeutic outcomes is patientspecific, established in collaboration with the
patient.
Outcome goals need to be realistic.
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Pharmacotherapeutics (cont.)
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Contraindications
Types of Drug Therapy
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Acute – acute illness
Maintenance – chronic disease maintenance
therapy
Supplemental (or replacement) – insulin, iron
Palliative – comfort measures
Supportive – maintain integrity of body functions
(fluid/electrolytes, blood products)
Prophylactic – vaccines, antibiotics
Empirical – antibiotics before seeing a culture test
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Pharmacotherapeutics (cont.)
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Monitoring – what to look for
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Therapeutic action – beneficial effects
Adverse effects – predictable undesirable effects
Toxic effects – undesirable effects due to over
abundance of drug (poisonous qualities)
Therapeutic index – ratio of toxic level to
therapeutic level (determines safety of a drug);
narrow/large or low/high; “therapeutic window”
Drug concentration – or drug levels (blood or urine
specimens)
Patient condition – weight, special population,
concurrent illness….
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Pharmacotherapeutics (cont.)
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Tolerance: decreasing response to repeated
drug doses
Dependence: physiological or psychological
need for a drug
Physical dependence: physiological need for
a drug to avoid physical withdrawal
symptoms
Psychological dependence (addiction):
obsessive desire for a drug
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Pharmacotherapeutics (cont.)
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Drug interactions – with other drugs or food
Additive effects – total effect of both
Synergistic effects – greater effect than both;
one enhances the other
Antagonistic effects – less effect than both
Incompatibility – cannot be given together;
chemical deterioration of the one or both
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Pharmacotherapeutics (cont.)
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Adverse drug event – broad term for an
undesirable occurrence involving medications
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Medication error – compromise 10 rights
Adverse drug reaction – unexpected reaction that
occurs at therapeutic levels of a drug
• Allergic reaction – hypersensitivity reaction
• Adverse drug withdrawal event – during withdrawal
• Idiosyncratic reaction – unexpected occurrence in patient
• Drug interaction – increased or decreased effect of one
drug on another
• Other drug effects – teratogenic, mutagenic, carcinogenic
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Pharmacotherapeutics (cont.)
• Ten Rights of medication administration
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Right drug for Right
Medication
Right dose
Right time
Right route
Right patient
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Right reason
Right documentation
Right evaluation for right
assessment
Right patient education
Right to refuse
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Pharmacotherapeutics (cont.)
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Medication processes where errors can
occur:
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Prescribing
Dispensing
Administering
Monitoring
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Pharmacotherapeutics (cont.)
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Other drug effects
Teratogenic – fetal defects
Ø Mutagenic – permanent change in genes
(radiation)
Ø Carcinogenic – cancer causing (excessive
hormone therapies)
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Pharmacognosy
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The process of identifying medicinal plants
and their ingredients, pharmacological
effects, and therapeutic efficacy
Four main sources for drugs: plants, animals,
minerals, and laboratory synthesis
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Pharmacoeconomics
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Study of the economic factors influencing the
cost of drug therapy
Cost–benefit analysis
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Toxicology
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Science of poisons and unwanted responses
to both drugs and chemicals
Clinical toxicology deals specifically with the
care of poisoned patients.
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Pharmacogenetics
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The study of the genetic basis for variations in
the body’s response to drugs, with a focus on
variation related to a single gene
See ethnocultural implications - e.g. G6PD
deficiency (drug induced hemolysis)
Pharmacogenomics surveys the entire genome
for determinants of drug response
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