L 3 Pharmacokinetics 1 - Drug Absorption and Distribution Flashcards
Explain the term pharmacokinetics
The entrance of drugs into the body together with their subsequent fate
OR
How the body interacts with drugs
Identify the 4 processes that control the fate of drugs in the body
Absorption
Distribution
Metabolism
Excretion
Identify the 4 factors that govern drug uptake at absorption sites
Size
Solubility
Polarity
Transporters
What is a prodrug?
A drug with lipophilic substituents added to it so that it can pass through the cell membrane
What is bioavailability?
The fraction of the administered dose of a drug that is absorbed into the systemic circulation after first pass metabolism in the liver
What is Vdist?
The theoretical volume in which a drug spreads throughout the body
How do you calculate Vdist?
Vdist = Dose/plasma concentration (@t = 0)
Rank the areas of the body that a drug invades as Vdist increases?
Plasma Interstitial fluid Intracellular fluid Muscle Fat
What is Lipinski’s Rule?
Optimal oral absorption requires a drug dose to be under 500g/mol
Name two ways of measuring a drug’s ability to be absorbed?
LogP (Partition coefficient)
Polar Surface Area (PSA)
What is “Egan’s Egg”?
An oval shape on the LogP vs PSA curve where most orally administered drugs lie
Are Acidic drugs protonated or deprotonated in acidic environments?
Protonated (uncharged)
Are basic drugs protonated or deprotonated in acidic environments?
Protonated (positively charged)
Where is P-gp found, and what is its role in drug absorption?
P-gp is found in gut epithelial cells
P-gp actively expels lipophilic drugs from the epithelial cells into the intestinal lumen
How are drugs stored in the blood?
They are bound to albumin
