pharmacokinetics Flashcards
Pharmacokinetics
absorption, distribution, and metabolism, and excretion
Pharmacodynamic
drug concentration at site of action, therapeutic and AE- what the drug does to the human body
bioavailability
ranking
IV, SL, ODT, IR, ER
micronized
method used to increase the dissolution rate is to reduce particle diameter, which increase surface area
bioavailability
formula
10 0x (AUC-extravascular/AUC-intravenous) x
(Dose-intravenous/Dose- extravascular)
distribution
drug molecules moving from the systemic circulation to various tissue and organs.
factors that favor passage across membranes and greater drug distribution
and greater distribution:
- high lipophilicity
- low molecule weight
- unionized status
- low protein binding
if drug is high protein bound (>90%) and serum albumin is low (<3.5 g/dL)
higher percentage of drug will be in the unbound form (increased risk for ADR)
protein bound compounds
… many out their but common is phenytoin, calcium
calcium corrected formula
Ca(corrected)= Ca(reported-serum) + [(4.0 - albumin) x (0.8)]
phenytoin corrected
Phenytoin mcg/ml (corrected)=
(total phenytoin measured)/[(0.2 x albumin)+0.1)]
metabolism phase I
oxidation, reduction, and hydrolysis
metabolism phase II
conjugation
Cl
Cl =
elimination rate (mg/hr)/Concentration (mg/L)
dose adjustment for Michaelis-Menten kinetics
most drugs follow first-order kinetics
- at stead state, doubling the dose approximately doubles the serum concentration
some drugs (phenytoin, theophylline, and voriconazole) follow Michaelis-Menten (also called non-linear, saturable or mixed-order) kinetics
- doubling the dose of these meds can more than double the serum concentration
—-> using proportion to calculate a new dose is not appropriate
—-> dose adjustment must be made cautiously to avoid toxicity
