1. Pharmacokinetics Chapter 4
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2. Pharmacokinetics Four basic pharmacokinetic processes are Absorption
Distribution
Metabolism
Excretion
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3. Factors Affecting Drug Absorption
Rate of dissolution
Surface area
Blood flow
Lipid solubility
pH partitioning
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4. Routes of Administration
Two major groups
Enteral
Via gastrointestinal tract
Parenteral
Outside the gastrointestinal tract
Usually referred to as “by injection”
Common routes—intravenous, subcutaneous, intramuscular
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5. Drug Distribution Factors influencing distribution are
Blood flow to tissue
– Exiting the vascular system
– The blood-brain barrier
– Placental drug transfer
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6. Drug Metabolism Biotransformation
Enzymatic alteration of drug structure
Liver—primary site of drug metabolism
P450 system (cytochrome P450)
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7. Drug Metabolism—Implications
Therapeutic consequences are
Accelerated drug excretion
Drug inactivation
Increased therapeutic action
Activation of prodrugs
Toxicity variations
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8. Special Considerations in Drug Metabolism
Age
Induction of drug-metabolizing enzymes
First-pass effect
Nutritional status
Competition between drugs
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9. Drug Excretion Removal of drug from the body
Kidney—via three processes
Glomerular filtration
Passive tubular reabsorption
Active tubular secretion
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10. Time Course of Drug Responses
Plasma drug levels
Minimum effective concentration (MEC)
Toxic concentration
Therapeutic range
Drug half-life
Loading dose
Maintenance dose
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11. The time for the amount of drug in the body to decrease by 50%
Drug Half-life
The time for the amount of drug in the body to decrease by 50%
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