Pharmacokinetics/Dynamics EXAM REVIEW Flashcards
What is the definition of oxidation?
Loss of electrons; phase I reaction
What is reduction?
Gain of electrons: Phase I reaction
What is Hoffman degradation?
Example of non-organ metabolism
Site of metabolism is PLASMA
What is Hydrolysis ?
Splitting molecule with the addition of water/ PHASE I
What is the relationship between ph and pKa.
When pH=pKa, 50% of the drug is ionized and 50% in non- ionized.
Lower pKa stronger acid, Higher pKa stronger base.
How does ph and pKa relationship affect weak bases and weak acids?
- A general rule with weak bases states when the pKa minus pH < 0, then most of the drug will be in the non-ionized form.
- With weak acids the opposite is true. pKa minus pH < 0 then most of the drug will be in the ionized form.
What percentage of cardiac output is distributed to each tissue compartment?
HIGHLY PERFUSED (lungs, heart, brain, kidneys, liver) ~ 75%
- Explain when protein binding becomes a concern to the clinician?
- Protein binding and Vd
- Protein binding and metabolism
- Protein binding and lipid solubility
- when is alteration important
- Protein binding effects Vd because only
unbound drug can cross cell membranes.
Therefore the Vd is inversely related to
protein binding. - Only unbound drug can undergo
metabolism and glomerular filtration - Extent of protein binding directly related to
the lipid solubility - Alterations in protein binding are only
important for drugs that are highly
protein bound.
- What are methods of metabolism? What are considered to be phase 1? What are considered to be phase 2
Phase 1 (ORH)
Oxidation, reduction and hydrolysis are
Phase II reaction –> CONJUGATION
6.Which routes of drug administration undergo hepatic first pass effect? Which do not?
1.Drugs that undergo large first pass hepatic
effect (lidocaine, propranolol) PO and IV doses very different
2. AVOID first pass effect
Include sublingual, buccal and nasal route, IV
3. Drugs administered into to LOWER RECTUM avoid the first pass effect
- What drug characteristics will affect Vd?
Lipid solubility, protein binding, molecular
size.
• Drug with LOW LIPID SOLUBILITY and HIGH PROTEIN BINDING will have a LOW Vd
Vd is _______to protein binding
Inversely proportional
- Define zero order kinetics?
Definition
When does it occur?
Result of
A constant amount of drug in cleared per unit of time regardless of plasma concentration
Occurs when the plasma concentration of
drug exceeds the capacity of metabolizing
enzymes.
• Result of saturating the available enzymes
at high drug concentrations of some
compounds.
What drugs undergo zero order kinetics?
Alcohol, Aspirin, and Phenytoin
- Define first order kinetics? What drugs undergo first order kinetics?
Most drugs will follow linear of first-order
kinetics.
• Constant fraction of drug is metabolized
per unit of time.