M1: Pharmacokinetics Flashcards
Time course of drug in the body. Encompassing absorption, distribution, metabolism & excretion. What body does to the drug. Determine the optimal formulation of a drug, dose & dosing frequency during drug development.
Pharmacokinetics
Entry of drug from site of admin to systemic circulation
Absorption
Biotransformation
Metabolism
Entry of drug to the tissues
Ditribution
Mode of exit of drug from the body
Excretion
Travel of drug across cellular membranes. Dependent on solubility, surface area, concentration gradient, tissue vascularity & ionization.
Permeability
Correlates the ability of a drug to cross cell membrane
Solubility
Ability to pass through lipid bilayers
Lipid solubility
Pass in aqueous phases
Water solubility
Ratio of lipid to aqueous solubility
Partition coefficient
The higher the partition coefficient, the more the ______ the drug.
Soluble
Determines the percentage of ionization. Drugs are either weak acids or weak bases & can exist as charged or neutral particles in equilibrium, depending on pH & pKa.
Henderson Hasselbach Equation
Increases renal clearance of drugs
Ionization
Is usually down a concentration gradient
Drug permeation
The greater the concentration gradient, the _______ the drug permeation.
Faster
Is the density of blood supply & speed of blood flow. There
relationship is directly proportional.
Tissue vascularity
Is the available area for permeation.
Surface area
The greater the surface area, the _______ the diffusion.
Faster
Length of the diffusion path
Thickness
Mechanism of Drug Passage Across Membranes
Passive, Facilitated, Active & Pinocytosis
Charged particles. Water soluble molecules are excluded from crossing many barrier.
Aqueous solubility
Within large compartments. Involves crossing of molecules across a tight junction. From area of higher to lower concentration. Plasma protein bound drugs cannot permeate thru aqueous process.
Aqueous diffusion
Entry into cells by very large substances (uses energy)
Endocytosis
For an orally administered drug, Absorption depends on
Disintegration, Dissolution & Diffusion
