Pharmacology and drug disposition
maandag 4 september 2017 13:54
Pharmacology: The study of the effects of drugs on the function of living systems, so not only in
humans
Drugs: Chemical substance, other than a nutrients or essential dietary ingredient, which, when
administered to a living organism, produces a biological effect
You can study pharmacology on the following levels:
- Molecular
- Celullar
- Organ
- Organism
- Family
- Population
Pharmacodynamics = what the drug does to the body
-> Targets e.g. receptors and exert a desirable effect
Pharmacokinetics = what the body does to the drug
-> Distribution of the drug (ADME)
Efficacy: is the relationship between receptor occupancy and the ability to initiate a response at
the molecular, cellular, tissue or system level.
Potency: a measure of drug activity expressed in terms of the amount required to produce an
effect of given intensity.
Lectures Pagina 1
,Agonist: induces active conformation of receptor protein
-> Full agonist: large stimulus to cellular signaling machinery: large effect
-> Partial agonist: small stimulus to cellular signaling machniery: small effect
Antagonist: occupies receptor without conformational changes
Inverse agonist: an inverse agonist decreases the activity below basal level, which can be
achieved with constitutive active receptors.
-> It works on already active proteins and decreases its activity to a negative activity
Reversible competition: Dose-dependent process. Presence of the highest concentration 'wins'.
Binding is reversible.
Irreversible competition: Not a dose-dependent process, includes irreversible binding. Desired
efficacy will not be reached.
Therapeutic window:
A small therapeutic window gives a higher chance of excreding the toxic value.
ED50: Median effective dose
TD50: Median toxic dose
'The dose makes the poison'
Absorption
Lectures Pagina 2
,Absorption
Distribution
Metabolism
Excretion
-> Major organs involved in drug disposition:
- Instestine (absorption)
- Liver (metabolism)
- Kidney (elimination)
○ Other: Brian, testis, placenta
The therapeutic window and ADME between persons differ. Therefore there has to be taken
care with dosage of new drugs.
High levels can sometimes be reached within a short timespend.
Kidneys and muscles have the highest blood rate of the body. This plays an important role
during the distribution phase.
There are two phases of metabolism:
Lectures Pagina 3
, A prodrug is a medication or compound that, after administration, is metabolized (i.e. converted
within the body) into a pharmacologically active drug.
Example Clopidogrel:
Clopidogrel is used to reduce the risk of heart disease and stroke in those at high risk.
Clopidogrel acts by inhibiting the ADP receptor on platelet cell membranes.
It has to be activated by cytochrome P450 to create an active metabolite, which can decrease
the platelet activation and thrombus formation.
So mutation of cytochrome P450 will have consequences for the activation of clopidogrel.
-> Cytochrome P450 is absorbed at a wave length of 450nm, this created its name.
Example paracetamol:
The metabolites of acetaminophen (paracetamol) results in toxic metabolites (NAPQI):
Pharmacokinetic parameters:
- Half-life (T1/2)
○ The time required to decrease the drug plasma concentration by 50%
○ Does not say anything about the concentration in the target organ!
- Distribution volume (Vd)
○ The theoretical voluma that would be necessary to contain the total amount of an
administered drug at the same concentration that is observed in the blood plasma
○ Vd can reach infinity if the component is bound with very high efficacy
- Bioavailability (F)
○ The extent to which a drug (or metabolite) enters the systemic circulation, therby
gaining acces to the site of action.
- AUC: area under the curve
○ The amount of a drug that enters into the systemic circulation in a given period
Intermittent drug administration and steady-state
Lectures Pagina 4
maandag 4 september 2017 13:54
Pharmacology: The study of the effects of drugs on the function of living systems, so not only in
humans
Drugs: Chemical substance, other than a nutrients or essential dietary ingredient, which, when
administered to a living organism, produces a biological effect
You can study pharmacology on the following levels:
- Molecular
- Celullar
- Organ
- Organism
- Family
- Population
Pharmacodynamics = what the drug does to the body
-> Targets e.g. receptors and exert a desirable effect
Pharmacokinetics = what the body does to the drug
-> Distribution of the drug (ADME)
Efficacy: is the relationship between receptor occupancy and the ability to initiate a response at
the molecular, cellular, tissue or system level.
Potency: a measure of drug activity expressed in terms of the amount required to produce an
effect of given intensity.
Lectures Pagina 1
,Agonist: induces active conformation of receptor protein
-> Full agonist: large stimulus to cellular signaling machinery: large effect
-> Partial agonist: small stimulus to cellular signaling machniery: small effect
Antagonist: occupies receptor without conformational changes
Inverse agonist: an inverse agonist decreases the activity below basal level, which can be
achieved with constitutive active receptors.
-> It works on already active proteins and decreases its activity to a negative activity
Reversible competition: Dose-dependent process. Presence of the highest concentration 'wins'.
Binding is reversible.
Irreversible competition: Not a dose-dependent process, includes irreversible binding. Desired
efficacy will not be reached.
Therapeutic window:
A small therapeutic window gives a higher chance of excreding the toxic value.
ED50: Median effective dose
TD50: Median toxic dose
'The dose makes the poison'
Absorption
Lectures Pagina 2
,Absorption
Distribution
Metabolism
Excretion
-> Major organs involved in drug disposition:
- Instestine (absorption)
- Liver (metabolism)
- Kidney (elimination)
○ Other: Brian, testis, placenta
The therapeutic window and ADME between persons differ. Therefore there has to be taken
care with dosage of new drugs.
High levels can sometimes be reached within a short timespend.
Kidneys and muscles have the highest blood rate of the body. This plays an important role
during the distribution phase.
There are two phases of metabolism:
Lectures Pagina 3
, A prodrug is a medication or compound that, after administration, is metabolized (i.e. converted
within the body) into a pharmacologically active drug.
Example Clopidogrel:
Clopidogrel is used to reduce the risk of heart disease and stroke in those at high risk.
Clopidogrel acts by inhibiting the ADP receptor on platelet cell membranes.
It has to be activated by cytochrome P450 to create an active metabolite, which can decrease
the platelet activation and thrombus formation.
So mutation of cytochrome P450 will have consequences for the activation of clopidogrel.
-> Cytochrome P450 is absorbed at a wave length of 450nm, this created its name.
Example paracetamol:
The metabolites of acetaminophen (paracetamol) results in toxic metabolites (NAPQI):
Pharmacokinetic parameters:
- Half-life (T1/2)
○ The time required to decrease the drug plasma concentration by 50%
○ Does not say anything about the concentration in the target organ!
- Distribution volume (Vd)
○ The theoretical voluma that would be necessary to contain the total amount of an
administered drug at the same concentration that is observed in the blood plasma
○ Vd can reach infinity if the component is bound with very high efficacy
- Bioavailability (F)
○ The extent to which a drug (or metabolite) enters the systemic circulation, therby
gaining acces to the site of action.
- AUC: area under the curve
○ The amount of a drug that enters into the systemic circulation in a given period
Intermittent drug administration and steady-state
Lectures Pagina 4
