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 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 half- life 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?