Core Concepts in Pharmacology
Chapter 5
Pharmacokinetics
Therapeutic effect and target cells
• What is the relationship between therapeutic
effect and target cells?
• What is the greatest barrier to achieving the
therapeutic effect?
• What physiologic processes hinder the
achievement of therapeutic effects?
Substance Passage Through Plasma
Membranes
• What role does diffusion play in achieving the
therapeutic effect?
• Compare and contrast the two processes
involved in diffusion.
Four Components of Pharmacokinetics
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Absorption
Distribution
Metabolism
Excretion
What do you remember about these
processes?
What do you think?
• What other organs are involved in excretion?
• What effect will liver or kidney impairment have
on the pharmacokinetics of medication.
• What are the implications for the prescriber?
• What are the implications for the nurse
administering the prescribed drugs?
First Pass Effect
• Figure 5.4
What is the problem with the first pass effect?
What can be done to bypass the first pass
effect?
Plasma Proteins and Drug Distribution
• Drugs bind with plasma proteins
– Drug protein complexes
– Capillary membranes impermeable
– Drug does not reach target cells
• Drugs and other agents compete for plasma
proteins
– Affinity
– Increasing blood levels
• Toxicity
Therapeutic response and plasma drug
level
• Direct relationship
• What nursing responsibility is essential when
administering drugs with low safety profiles?
• Define:
– Minimum effective concentration
– Toxic concentration
– Therapeutic range
Achieving and Maintaining Therapeutic
Concentrations
•
•
•
•
Repeated dose scheduling
Drug accumulates in blood stream
Plateau reached
Amount administered = amount excreted
Differentiate between Loading Dose
and Maintenance Dose
• Loading Dose
– Higher amount of given
drug
What is the benefit to
administering a loading
dose?
• Maintenance Dose
– Doses administered at
intermittent (scheduled)
times
What is the purpose of
maintenance doses?
Plasma half-life (t ½)
• Describes drugs duration of action
• Describe h0w the frequency of dosing differs
depending upon the drugs half-life.
• How does renal or liver disease affect drug
half-life?
Application problem
• ciprofloxacin hydrocholride (Cipro) has a halflife of 4 hours.
• You administer a 500 mg oral dose of
ciprofloxacin. How long will it take to have
less than 1o mg of that dose circulating?