Introduction To Pharmokinetics Flashcards
What is pharmacokinetics?
The movement of drugs within the body
What is pharmacodynamics?
The effect of drugs on the body
What is bioavailability?
The fraction of the drug that reaches the systemic circulation as intact drug
What is drug disposition?
All processes by which the body handles drugs
What is the ADME model?
A bsorption, D istribution, M etabolism, and E limination
What are most drugs classed as?
Weak acids or weak bases
What is drug-protein binding?
The reversible interactions of drugs with proteins.
What is the first-pass effect?
The extent to which a drug is removed by the liver during its first passage into the portal vein
What is the function of the epithelial cell layer?
To define the boundary of the body
What is the largest constituent of the human body?
Plasma
What are the different proteins that drugs can bind to
Proteins in the plasma, tissue components, RBCs.
What is the definition of pKa?
The pH where ionised and unionised forms of the weak acid or base are equal
What is absorption?
The extent to which intact drug is absorbed from the gut lumen into the portal vein
What separates each compartment?
Various barriers e.g epithelial cells
What are the non-covalent bonding forces involved in drug-protein binding?
Van der Waal’s forces, ionic bonding, hydrogen bonding.
What are cell membranes?
Barriers between compartments in the body
What are the different routes of drug administration?
Subcutaneous, Intramuscular, Oral, Intravenous, Intraarterial, Rectal, Vaginal, Transdermal, Sublingual, Intranasal, Intravitreal, Inhalational,
What is the volume of distribution
Extent of distribution in the body
What are the components of cell membranes?
Lipids, proteins, and carbohydrates
How is cell membrane formed
Lipid bilayer
How does the pKa value affect the strength of an acid or base?
Lower pKa value indicates a stronger acid or base, while higher pKa value indicates a weaker acid or base
What is the function of the intestinal wall and liver?
To prevent entry of xenobiotics into the body
Which proteins have binding sites selective for basic drugs?
Alpha 1-acid glycoproteins and Beta-globulins.
How is the volume of distribution used?
To calculate the dose for therapeutic drug concentration
What is the function of cholesterol in the cell membrane?
Affects membrane fluidity and stability
What is lipophilicity?
The ability of a molecule to dissolve in lipids
Where do lipid soluble drugs partition?
Into the lipid bilayer.
How is lipophilicity measured?
By the partition coefficient (Log P)
What determines the adequate drug concentration at the site of action?
Absorption and distribution
What does a higher Log P value indicate?
Higher lipophilicity and permeability
What is the volume of distribution (V)
The relationship between the total amount of drug in the body and the concentration of drug in the plasma.
What is the general rule for absorption of weak acids and weak bases in the intestine?
Weak acids are well absorbed from the acidic environment of the intestine as a larger fraction exists as the unionised form, while weak bases are absorbed more slowly as a larger fraction exists in the ionised form
What are the barriers to getting drugs into the systemic circulation following oral administration?
Cell membrane barriers
What is the principle of minimum hydrophobicity?
Designing drugs with low hydrophobicity to reduce toxicity
Give the equation for the volume of distribution
equation: V = Total amount of drug / Concentration of drug in plasma.
What is distribution in pharmacology?
The movement of drug molecules from the circulating blood to other areas of the body
What factors determine the ability of a drug to permeate the cell membrane barriers?
Lipophilicity and ionisation status
What is the volume of distribution of a drug if it is 100 L and the blood plasma concentration is 10 mg/L?
1000mg
What is the volume of distribution referred to as?
The ‘apparent’ volume of distribution.
What factors does drug distribution depend on?
Blood flow, concentration gradient, permeability of cell membranes, drug binding to plasma proteins or tissue components
What is the bioavailability of a drug?
The amount of drug that reaches the systemic circulation
What do proteins binding drugs act as?
A reservoir for drug transport and a pharmacologically inactive mass-transit unit
What is the effect of first-pass metabolism on drugs?
It reduces the bioavailability of drugs
What does distribution depend on?
Blood flow and protein binding
What is route of drug through oral administration and dissolution?
Mouth, oesophagus, liver, stomach, small intestine, colon
Equation for bioavailability:
Fraction absorbed into portal vein x fraction escaping through first pass
