introduction to pharmacokinetics 2 Flashcards
where does the metabolism of a parent drug primarily occur
the liver
clearance
Clearance describes the efficiency of irreversible elimination of the parent drug from the systemic circulation
formula for clearance(CL)
Elimination rate/ Plasma drug concentration
unit for clearance
unit for elimination rate
unit for plasma drug concentration
Lh^-1
mgh^-1
mgL^-1
the total rate of elimination
the sum of all routes of elimination
Xeno means?
foreign
examples of drugs that could be considered xenobiotic
Pesticides
Environmental pollutants
Industrial Chemicals
Food additives
which systems have the body evolved to rid itself of foreign substances
detoxification systems
When the drug has been metabolized it is said to have been………… or ……………, even if it’s metabolites are still in the body
cleared or eliminated
hepatic elimination
the process by which drugs and other foreign substances are modified, metabolized, and often detoxified by the liver (hepatic refers to the liver)
the major organ containing the greatest abundance and diversity of drug-metabolizing enzymes
the liver
why are lipophilic xenobiotics not excreted efficiently by the kidney?
Lipophilic (fat-soluble) xenobiotics are typically not efficiently excreted by the kidneys because the renal excretion process primarily favors water-soluble molecules. The kidneys filter and excrete substances from the bloodstream into the urine, and for a substance to be efficiently excreted, it must be water-soluble or must undergo specific processes to become more water-soluble
lipophilic xenobiotics can only be excreted after being?
metabolized
lipophilic xenobiotics are biotransformed into a new more polar entity called a
metabolite
name given to the process by which lipophilic xenobiotics are converted to a form that can be excreted efficiently by the kidneys
biotransformation
drug biotransformation can be classified into how many phases?
name them
2
phase I
phase II
phase I metabolism
Introduction or unmasking of a chemically reactive functional group (increases the polarity of the compound)
phase II metabolism
Conjugation of an endogenous molecule onto the functional group (further increases polarity of the compound)
which one between phase I and II metabolism involves catabolic reactions
phase I
which one between phase I and II metabolism involves anabolic reactions
phase II
is the metabolite that phase II metabolism results in active?
no, they are inactive
biliary elimination
is a process in which drugs, toxins, and waste products are excreted from the body via the bile produced by the liver
major metabolising organ in mammals
liver
do phase II reactions always follow phase I reactions
no
when do phase II reactions happen immediately without phase I reactions
when the parent molecule contains reactive groups like hydroxyl groups, amino group…etc
where do phase I reactions primarily occur
in the cytochrome P450 enzymes located in smooth endoplasmic reticulum membrane inside hepatocytes
where do phase II reactions primarily occur
the hepatocyte cytosol
in which organisms is Cytochrome P450 found, and in which tissues in these organisms can they be found
bacteria
plants
insects
mammals
virtually all tissues
functional unit of the kidney
the nephron
function of the nephron
to filter blood
the three important processes that occur in the nephron that make up the renal clearance of a drug
filtration
secretion
reabsorption
what are the undesired effects produced by a drug referred to as
adverse effects
the therapeutic concentration of a drug is aka
Minimum effective concentration (MEC) of that drug
the adverse concentration of a drug is aka
Minimum toxic concentration (MTC) of that drug
the therapeutic range of a drug
difference between the MTC and the MEC
purpose of the calculating the therapeutic range
Provides an indication of whether or not therapeutic drug monitoring is necessary
is the true dose of the drug the amount of strength swallowed
no
what is the true dose of a drug
amount available to have its effect
examples of therapeutic windows
non toxic
medium toxicity
highly toxic
difference between non toxic and highly toxic drugs
non toxic drugs have a large therapeutic window while toxic drugs have a narrow therapeutic window
what does the true dose of a drug depend on
dissolution of the drug
absorption of the drug
the drugs ability to survive metabolism
what could lead to reduced metabolism of a drug
Liver disease
Old age
Drug interactions
Inhibition of drug metabolising activities
what could lead to increased metabolism of drugs
liver enzyme inductions
formula for the rate of elimination
rate of renal excretion+ rate of hepatic metabolism
drugs are less likely to be metabolised or eliminated when bound to other molecules, like proteins, true or false
true
