Relationship Between Pharmacokinetic Parameters and Pharmacological Response Flashcards
Pharm. Alex Akinola
Define drugs.
Drugs may be defined as chemicals that alter physiological or biochemical processes in the body in a manner that makes them useful in the treatment, prevention, or cure of diseases.
What is pharmacokinetics?
Pharmacokinetics is the study of the time course or quantitative measurement of absorption, distribution, metabolism, and excretion of drugs.
What is distribution?
Distribution occurs when drug molecules that have entered the vascular system pass from the bloodstream into various tissues and organs such as the muscle or heart.
What is metabolism?
Metabolism is the chemical conversion of the drug molecule, usually by an enzymatically mediated reaction, into another chemical entity referred to as a metabolite
Define pharmacodynamics.
Pharmacodynamics is the discipline that quantifies the relationship between drug concentration at the site of action and the drug’s pharmacological effect.
Pharmacodynamics is the relationship between drug concentration and pharmacological response.
What is excretion?
Excretion is the irreversible removal of drug from the body and commonly occurs via the kidney or biliary tract.
List the independent pharmacokinetic parameters.
i. Time
ii. Volume of distribution
iii. Dose
List 3 dependent pharmacokinetic parameters.
i. Half-life
ii. Plasma concentration
iii. Bioavailability
iv. Elimination rate
v. AUC
What is half-life?
The half-life (t½) of drug is the time required for the concentration of the drug in the plasma or the total amount in the body to decrease by 50%.
What is the formula for half-life (t1/2)?
t1/2 = 0.693/k
where k = CL/Vd
Thus t1/2 = O.693Vd/CL.
What is apparent volume of distribution (Vd)?
Apparent volume of distribution (VD) is the hypothetical volume of body fluid in which the drug is dissolved.
Cp = Db/Vd
Where:
Vd = volume of distribution
Cp = plasma drug concentration
Db = Dose (amount of drug in the body)
What is clearance?
It is defined as plasma volume in the vascular compartment that is cleared of drug per unit of time.
It is a measurement of drug elimination from the body. (L/hr or mL/min)
It is also the rate at which an active drug is removed from plasma.
_________________ is the major route of drug elimination for polar drugs, water-soluble drugs, drugs with low molecular weight (< 500), and drugs that are bio-transformed slowly.
Renal drug clearance
___________ is the most important pharmacokinetic parameter because it determines the maintenance dose (MD) that is required to obtain a given steady-state serum concentration (Cp.ss).
Clearance
Define Clinical Pharmacokinetics.
Clinical pharmacokinetics is the application of pharmacokinetic concepts and principles in humans in order to design individualised dosage regimens that optimise the therapeutic response of a medication while minimising the chance of an adverse drug reaction.
