2. Pharmacokinetics and Pharmacodynamics Flashcards
Phases in drug-body interactions
Absorption
Clinical effect
Metabolism
Excretion
Routes of drug administration and examples (2)
Enteral (via gut - oral)
Parenteral (IV, IM, SC, TD, inhalation)
Advantages of oral drug administration
Socially acceptable
Disadvantages of oral drug administration (4)
Slow onset
Variable absorption
First-pass metabolism
Least reliable
Factors accepting oral absorption (5)
Lipid solubility Drug formulation GI motility Interactions with other substances in the gut GIT disease
Definition and effect of first-pass metabolism (2)
Orally administered drugs can reach systemic circulation after passing through the liver once
Alters drug concentration
Types of liver metabolism, effect and example (2)
Drug inactivation - more required orally for desired effect, GTN
Drug activation - activates inactive form. Acyclovir
Advantages of parenteral drug administration (2)
Predictable plasma levels (when administered)
No first-pass metabolism
Disadvantages of parenteral drug administration (3)
More severe allergic reaction
Access difficulties/self-medication
Higher drug costs
Definition of bioavailability
Proportion of ingested drug available for clinical effect
Bioavailability is modified by (4)
Dosage form
Destruction in the gut
Poor absorption
First-pass metabolism
Explanation of volume of distribution
How much of the body the drug is diluted in (different compartments)
Drug distribution is affected by (2)
Lipid binding - slow release from accumulation
Drug binding to plasma proteins (bound drug is inactive)
Definition of drug metabolism
Preparing drug for elimination from the body
Action and definitions of drug metabolism (2)
Phase 1 reactions - inactivates drugs
Phase 2 reactions - prepares for removal/removes from body
Types of phase 1 reactions (3)
Oxidation, reduction, hydrolysis
Types of phase 2 reactions
Conjugation - glucuronidation, sulfanation, methylation, acetylation, glutathione
Methods of drug excretion 4)
Renal (urine) - via RAAS
Liver (bile)
Lungs (gas exchange)
Others (Sweat, saliva)
Excretion disorders (2) and examples (2)
Renal disease - chronic renal failure
Liver disease - liver failure
Drug distribution compartment definitions (2)
Single compartment model - drug behaves as if evenly distributed throughout body
Two-compartment model - drug behaves as if in equilibrium with different body tissues
Pharmacokinetics involves (2)
Drug clearance
Repeated drug dosing
What does drug clearance involve (2)
Plasma half-life (t0.5)
First order kinetics/zero order kinetics
First order kinetics (4): Active/passive Elimination vs concentration Graph Plasma half life
Drug elimination/absorption is passive diffusion
Drug elimination is proportional to drug concentration
Logarithmic graph of elimination is a straight line
Plasma half-life is constant
Zero order kinetics (3):
Active/passive
Elimination vs concentration
Graph
Drug elimination is active and can be saturated by very high drug concentrations
Max. rate of elimination is constant regardless of concentration
Linear graph of drug elimination (constant amount eliminated per unit time)
Definition of drug accumulation
How the plasma concentration builds if repeated doses of a drug are given
Drug scheduling issues (2)
Too frequent - plasma levels may become toxic
Too infrequent - sub-therapeutic plasma levels and no clinical effect
