Pharmacokinetics And Drug Formulations Flashcards
What’s Pharmacodynamics (PD)?
Refers to effects of drugs on patients body (MOA)
Also used to explain effect of drug on organism eg bacterioSTATIC or bactericidal
Types of drug admin sites?
Intravascular admin
Extravascular admin
What’s Intravascular admin?
Where drug is placed directly into the blood either intravenously or intra-arterially
What’s extravascular admin?
Oral, sublingual, buccal, IM, SC, dermal, pulmonary, topical ocular, intraocular and rectal
Is there drug absorption when drug is admin intravascular admin?
No! (Drug is placed directly into systemic circulation)
What’s dissolution?
Oral dosage form dissolving in GI tract and drug is released from the dosage form
Why’s protective coating used in some drugs?
To limit drug degradation, which occurs primarily by hydrolysis
By preventing drug dissolution in acidic gut medium, but permits dissolution in basic medium of intestine
How is dissolution rate increased in drug with poor absorption?
To reduce particle diameter, which increases the surface area
What describes rate of dissolution?
Noyes-Whitney eqn
What determines rate and extent to which drug dissolves in GI fluid?
Solubility of drug
T/F? Only dissolved drug is absorbed into the body?
T
How does systemic absorption occur?
Passive diffusion - across gut wall
Active transport - via transport proteins
When does passive diffusion occur?
When there’s a high conc of drug in gut lumen and it moves to equalize drug conc (reach equilibrium) across the gut wall
Whats bioavailability?
Extent to which a drug is absorbed into systemic circulation
% of drug absorbed from extravascular admin RELATIVE TO intravascular admin
Howz bioavailability calculated?
Using Area under the plasma conc time curve (AUC)
How do u calculate absolute bioavailability (F)?
F (%) = 100 x (AUCextravascular/AUCiv) x (DOSEiv/DOSEextravascu)
What properties determine how drugs distribute evenly throughout the body?
Lipophilicity
Molecular weight
Solubility
Ionization status
Extent of protein binding
What’s the primary protein in the body?
Albumin
What’s the vol of distribution (V or Vd)?
How large an area in the pts body the drug has distributed into & is based on properties of that drug
Amt of drug in the body to conc of drug measured in plasma or serum
Formula of Vd?
Vd = amt of drug in body/ conc of drug in plasma
Conc of drug in body = amt of drug remaining in body x vol parameter
Vd formula in bolus IV injection?
Vd = dose/Co
Vd formula following oral dose?
Vd = (F x Dose)/(Kel x AUC)
F = bioavailability Kel = terminal elimination rate constant AUC = area under plasma conc-time curve
What’s clearance?
PK parameter that converts a conc of drug in the body to an amount eliminated per unit time
Rate of elimination = Cl x Conc
What’s half-life?
Time req for drug conc (and drug amt) to decrease by 50%
