4. Pharmacology
Pharmacokinetics Pharmacodynamics
Adsorption * How does the drug
Distribution interact with the cell?
Metabolism * How does the drug
Excretion cause a therapeutic effect?
What the body does What the drug does
to the drug to the body
5. Pharmacology
Pharmacokinetics Pharmacodynamics
Adsorption * How does the drug
Distribution interact with the cell?
Metabolism * How does the drug
Excretion cause a therapeutic effect?
What the body does What the drug does
to the drug to the body
13. Concept of Receptor
Some drugs do not require a receptor for their effect:
e.g.
antacid: - changes pH of stomach
aspirin: - forms covalent bond with enzyme
kaolin: - adsorbs toxin in the gastrointestinal tract
15. Concept of Receptor
cell
Drug Molecules
Langley 1878:
āDrug binds to a receptive substance on the cellā
(drugs must first bind to a receptor to produce their
action)
21. Main Families
of ReceptorsIon Channels
(open up for ions to pass)
G protein Coupled Receptors
(intracellular part of the receptor
activate or inhibit cellular proteins)
22. Main Families
of ReceptorsIon Channels
(open up for ions to pass)
G-protein Coupled Receptors
(intracellular part of the receptor
activate or inhibit cellular proteins)
Receptor Tyrosine Kinase
(phosphorylate intracellular proteins)
Intracellular Receptors
(enter nucleus,
promote gene transcription)
26. G-protein Coupled Receptor
Receptor
G proteins
MODERN DRUG DISCOVERY NOVEMBER 2004 p24-28
Receptor
G proteins
Inside
the
cell
Outside
the cell
Hormone
27. G-protein Coupled Receptor
Receptor
G proteins
MODERN DRUG DISCOVERY NOVEMBER 2004 p24-28
Inside
the cell
Outside
the cell
Activate or inhibit other proteins, leading to
final effect e.g. muscle contraction, enzyme
secretion, etc.
33. Drug-Receptor Binding
D = Drug R = Receptor
D + R DR Effect
Principle: Drug-receptor binding
follows the Law of Mass Action:
34. Drug-Receptor Binding
D = Drug R = Receptor
D + R DR Effect
Principle: Drug-receptor binding
follows the Law of Mass Action:
ā¢ D and R bind after they collide randomly
35. Drug-Receptor Binding
D = Drug R = Receptor
D + R DR Effect
Principle: Drug-receptor binding
follows the Law of Mass Action:
ā¢ D and R bind after they collide randomly
D + R DR
ā¢ After binding, D can dissociate from R
D + R DR
36. Drug-Receptor Binding
D = Drug R = Receptor
D + R DR Effect
At equilibrium, ( or )
association rate = dissociation rate
38. Drug-Receptor Binding
D + R DR
ā¢ At equilibrium, some of the D is binding to R
ā¢ If the number of R is constant,
then if D increases, DR also increases
D + R D R
D+ R DR
39. Drug Dose/Concentration &
Receptor Binding
D + R DR
Plot DR versus D:
100%
0
50%
DR ( %
of Receptor
bound to
Drug)
D (Drug Concentration)
40. Drug ā Receptor binding experiment
Receptor (in cell membranes)
+
drug
Wait for equilibriumā¦ā¦
45. Drug Dose/Concentration &
Receptor Binding
D + R DR
Plot DR versus D:
100%
0
50%
DR ( %
of Receptor
bound to
Drug)
D (Drug Concentration)
46. Drug Concentration &
Receptor Binding
D + R DR
Plot a graph of DR against D:
D (Drug Concentration) [or amount]
DR ( %
of Receptor
bound to
Drug)
100%
0
50%
48. Drug Concentration &
Receptor Binding
D (conc)
B (% Bound)
ā¢ Equation: B (amt bound) Bmax . D
D + Kd
100
50
0
Rectangular
Hyperbolic
Curve
49. Drug Concentration &
Receptor Binding
D (conc)
B (% Bound)
ā¢ Equation: B (amt bound) Bmax . D
D + Kd
ā¢ Kd = dissociation constant
- concentration of drug when 50% of the
receptors are bound.
100
50
0
Rectangular
Hyperbolic
Curve
50. Drug Concentration &
Receptor Binding
D (conc)
B (% Bound)
ā¢ Equation: B (amt bound) Bmax . D
D + Kd
ā¢ Kd = A measure of affinity of drug for receptor
Every drug that can bind a receptor has a Kd value for
that receptor.
100
50
0
Rectangular
Hyperbolic
Curve
51. Drug Concentration &
Receptor Binding
D (conc)
B (% Bound)
ā¢ Equation: B (amt bound) Bmax . D
D + Kd
ā¢ Kd = A measure of affinity of drug for receptor
The higher the affinity, the smaller the Kd
100
50
0
Rectangular
Hyperbolic
Curve
56. Drug Concentration/Dose
& Receptor Binding
B
(% receptor
bound)
100
50
0
0 5 10 20 30 40
D (Drug conc) (mg/mL)
Drug A
Drug B
Kd (Drug A) = 10 mg/mL
Kd (Drug B) = 5 mg/mL
57. Drug Concentration/Dose
& Receptor Binding
B
(% receptor
bound)
100
50
0
0 5 10 20 30 40
D (Drug conc) (mg/mL)
Drug A
Drug B
Kd (Drug A) = 10 mg/mL
Kd (Drug B) = 5 mg/mL
The higher the affinity, the smaller the Kd
58. Drug Concentration/Dose
& Receptor Binding
B
(% receptor
bound)
100
50
0
0 5 10 20 30 40
D (Drug conc) (mg/mL)
Drug A
Drug B
Drug B has a higher affinity for the receptor than Drug A, so
Kd for drug B is smaller.
Kd (Drug A) = 10 mg/mL
Kd (Drug B) = 5 mg/mL
59. Drug Concentration/Dose
& Receptor Binding
ā¢ Kd = dissociation constant : concentration of
drug when 50% of the receptors are bound.
= A measure of affinity of drug for receptor
- The higher the affinity, the smaller the Kd
66. Drug Dose &
Response/Effect
D + R DR Response
(ED50)
ED50 (effective dose 50%) = drug dose that give 50% of
maximum response
Response
(% max)
Drug Dose
100
50
0
A ādose response curveā
67. Drug Dose &
Response/Effect
D + R DR Response
ED50 (effective dose 50%) or EC50 (effective conc
50%) =drug dose or conc giving 50% of max response
Response
(% max)
Drug Dose or Concentration
100
50
0
A ādose response curveā
68. Drug Dose &
Response/Effect
D + R DR Response
Every drug that can bind a receptor to produce a
response has a EC50 or ED50 value for that response
Response
(% max)
Drug Dose or Concentration
100
50
0
A ādose response curveā
69. Drug Dose &
Response/Effect
(ED50)
Response
(% max)
Drug dose
100
50
0
A ādose response curveā
Plotting response versus dose: a rectangular
hyperbolic curve
Drug concentration(EC50)or
70. Drug Dose & Response
Plotting drug dose/concentration using log scale
instead of arithmetic/linear scale
72. Drug Dose & Response
Plotting response versus log dose (or log conc):
sigmoidal log-dose response curve
100
50
0
Log dose
Response
(% max)
ā¢ Most important type of graph in pharmacology:
ā¢ For comparing different drugs
-9 -8 -7 -6 -5 -4
74. Drug Dose & Response
100
50
0
Response
%
Response
%
[Drug Conc]
100
50
0
(arithmetic scale) (log scale)
Reasons to plot semi-log dose-response curves:
ā¢ Easier to interpret:
expands the scale at low concentrations
75. Drug Dose & Response
100
50
0
Response
%
Response
%
[Drug Conc]
100
50
0
(arithmetic scale) (log scale)
Reasons to plot semi-log dose-response curves:
ā¢ Easier to interpret:
expands the scale at low concentrations
76. Drug Dose & Response
100
50
0
Response
%
Response
%
[Drug Conc]
100
50
0
(arithmetic scale) (log scale)
Reasons to plot semi-log dose-response curves:
ā¢ Easier to interpret:
and compresses the scale at high concentrations.
77. Drug Dose & Response
100
50
0
Response
%
Response
%
[Drug Conc]
100
50
0
(arithmetic scale) (log scale)
Reasons to plot semi-log dose-response curves:
ā¢ Easier to interpret:
ā¢Linear between 20 to 80% of maximal response
- the dose range of drugs most commonly studied
78. Summary
ā¢ Definition of pharmacodynamics
ā¢ Concept of receptor
ā¢ Concept of affinity of a drug for a receptor
ā¢ Drug binding curve: definition of Kd
ā¢ Dose response curve: definition of ED50(orEC50)
ā¢ Plotting log dose-response curves
79. ā¢ What is potency?
ā¢ What is efficacy?
ā¢ What is an agonist?
ā¢ What is an antagonist?
2013 contd good feedback as lecturer, mention during lect which curve get which data, in revision class show all wrong interpretation cos cannot get Kd from response curve etc. Made EOB SEQ on which drug higher affinity from this curve (its response curve) and which more potent/effic- 121 students- max 15 marks, 7 got either 1 or 0 mark.
Only 4 (3.3% of students) got 12 marks or more (able to say this curve cannot get affinity info: Yap Wen Nee, viviene jane, dylan harry, chai chang xian. Ave mark 5.4 (fail)
2013 45 min. no interaction, just give analogies- affinity for food, students bump into chairs, sit and stand. One asked is dose response related to michaelis menten enzyme kinetics- reaction rate v increases with substrate conc. Max is vmax, and substate conc for half Vmax is Km. http://medicaltextbooksrevealed.s3.amazonaws.com/files/11189-53.pdf āThe same mathematical relationships that define how a drug (ligand) interacts with a receptor to elicit or diminish a biological response also governs the ways in which substrates (ligands) interact with enzymes to generate metabolic end products. In fact, the terms KD and Emax (ceiling effect) can easily be redefined as Km and Vmax, which you recall from Michaelis-Menten enzyme kinetics.ā āDose ā response curves and enzyme kinetics. These are the same. The familiar dose-response curves are based on the Michaelis ā Menten model of enzyme substrate interactionā. http://www.frca.co.uk/article.aspx?articleid=101185. a dose response curve can obey first order Hill equation (Hill coefficient = 1) A first-order Hill function (means no cooperativity- binding of ligands are independent of each otherās binding) is sometimes called a Michaelis-Menten function).
āThe fact that dose-response curves varied so much made pharmacology different from biochemistry. The concentration of a drug which produced a half-maximum response from a tissue, EC50, was not constant: with powerful agonists a maximum response was produced from the activation of only a small proportion of receptors.āhttp://www.pa2online.org/articles/?volume=1&issue=2. āSo the dissociation constant is a measure of the affinity of the drug for its receptor, just like the Michaelis-Menten constant (Km) is a measure of the affinity of a substrate for its enzyme. At equilibrium, the reaction can also be expressed by this equation which takes the
same form as the Michaelis-Menten equation. āDrug concentration- effect relationship can be described by: 1) Michaelis-Menten equation for enzyme-substrate reactionā. So far can say if based on single site and no cooperative binding then dose response curve is similar to michelis menten where velocity become effect and EC50 is Km.
End lect can use class name list to read out names of 4 students to ask them define at next class what is potency, efficacy, agonist and antag.
A receptor can be any cellular macromolecule to which a drug binds to initiate its effect. Cellular proteins that are receptors for endogenous regulatory ligands (hormones,
growth factors, neurotransmitters) are the most important drug receptors. Other receptors include enzymes (e.g., acetylcholinesterase), transport proteins (e.g., Na+,K+-ATPase), structural proteins (e.g., tubulin), and nucleic acids.
When the relationship between receptor occupancy and response is linear, KD = EC50. If there is amplification between receptor occupancy and effect, such as if the receptor has catalytic activity when the receptor ligand is bound, then the EC50 lies to the left of the KD.
2012 50 min. student ask can binding curve also do semi log, and is binding curve same shape as response curve.- yes binding curve in log appear in lecture 2, will inform students there. In 3rd lect can give eg of real binding and response curve from journals, see same shape.
2011 had question why log scale is 1,10,100, 1000 ā does log make scale increase very fast (aside from initial one to 3 is sparser and 3 to 10 is compressed)? (yes it increase exponential not arithmetical) And we say is log scale but never need to get antilog, just read off, though axis is officially log? (yes cos never took log, just plot on a scale with different intervals)
From the questions in āwhat else I want to knowā slips, some wonder how the binding/response expt is done so I put the binding expt pictorial in formative assessment
2010 45 min. supported by hard copy notes. if at end want to emphasise the impt of differentiate binding and effect curve then before show summary, show the diagram of drugs near the receptor with effect- put a dividing line and say again there are 2 different expt, 2 different part of the process, and first thing when see graph is ask what curve, then can know what info can get. Then I got 4 students to each read up on potency, effic, agonist and antag.
Concept of receptor and how to analyse D-R binding
How the drug at site of action produces an effect: receptor bind, quantitative analysis for comparing different drugs
Concept of receptor and how to analyse D-R binding
Note kinetic still occur after work at site, but it does mean dynamic cannot occur until drug arrive at site of action
How the drug at site of action produces an effect: receptor bind, quantitative analysis for comparing different drugs
Take a drug not just to metab and excrete it but cos you want it to act on body.
Take a drug not just to metab and excrete it but cos you want it to act on body.
Inhib cyclooxegenase which convert AA to PG, TX and Prostacyclin
Before showing the main types of receptor, would be clearer to explain that in general drug bind receptor which then activate downstream signals to amplify and generate the effect.
Before showing the main types of receptor, would be clearer to explain that in general drug bind receptor which then activate downstream signals to amplify and generate the effect.
Not just stand at door, come in, start the action
Receptors are types of doors, once activated, action starts
receptor for the epidermal growth factor (EGF) ā receptor tyr kinase
ifn= interferon receptor- class II cytokine receptor family. The Janus (JAK) family tyrosine kinases Tyk2 and Jak1 are constitutively associated with the IFNAR1 and IFNAR2c receptor subunits, respectively. Ligand binding results in the phosphorylation and activation of Tyk2 and Jak1
Tnf receptor- TNF is a cytokine which may induce either cell proliferation or apoptosis. TNF binds TNF Receptors (TNFRs), which are members of a superfamily of proteins known as Death Receptors, resulting in receptor aggregation and recruitment of adapters (i.e., TRAF [TNF Receptor-Associated Factor] proteins) TNFR complex formation activates Caspase 8, the SAP Kinase pathway (dependent on recruitment of Daxx), and the NFĪŗB pathway (which controls apoptosis versus proliferation).
Nicotinic cholinergic receptor
- Composed of 5 peptide subunits: 2Ī±, 1Ī², 1Ī³, 1Ī“
Receptor on muscle fibre eg respiratory muscles- how does it contract. Nerve release NT bind to receptor.
The two binding sites for AcCho are nonidentical and can
be distinguished by differential binding of some competitive
antagonists. In particular, d-tubocurarine (TC) binds with
dissociation constants that differ by -100-fold
May need show more cascade and recoupling, else some wonder what is G doing
May need show more cascade and recoupling, else some wonder what is G doing
May need show more cascade and recoupling, else some wonder what is G doing
Affinity is bind with tenacity
Like all stand and move, but eyes close, move quietly so have random collisions.
randomly meet at party but after talk, can dissociate and meet others
there are some binding and others unbinding- so arrow in 2 direction, at equib, rate is equal. at any moment, some (not all) are bound
At first more DR formed. Later, more DR dissociate. At equib, rate is same.
Rate of nos sitting down is same as nos standing up from sitting.
Illus; 10am shopping centre open and number of people inside increases. Till 11am there is 100 inside though 30 enter from 11-12 yet only 100 total inside- cos 30 also leave- equib. But no matter how many inside (30, 50 then 100, majority are at one shop, the most popular one (MPH book, Guess jeans, CD,DVD, Nike shoes) then customer has highest affinity for that store. Lower affinity for other store and no affinity for certain store.
Collide = all move blindfold and no noise
Case of where nos of people of shopping centre the same though new one go in, cos some go out, and more will be at fav store- higher affinity
Till all receptors bound
Till all receptors bound
Can be dose or conc. Dose is what you give, conc is level in blood. More dose, more conc. Plot whichever
Can be dose or conc. Dose is what you give, conc is level in blood. More dose, more conc. Plot whichever
For ease just say receptor binding
If you bring in more student (eg 1000 student in this room of 100 chairs) eventually every chair will be occupied- 100% receptor bound.
Draw higher affinity plot to compare
Draw higher affinity plot to compare
Draw higher affinity plot to compare
Draw higher affinity plot to compare
Draw higher affinity plot to compare
Can you do this
Can you do this
What is kd?
Can you do this
Now draw a 2nd drug of higher affinity
Can you do this
Can you do this
Can you do this
Can you do this
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted.
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted.
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted.
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted.
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted.
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
In clinical use of drug we donāt give patient one range, only one dose. We give range in pharmacol expt to see the property of the drug. If give more drug will not increase response cos every system has a max, like you cannot increase HR to 1 million beat per min, and cannot make car go faster when at max speed by putting more petrol (need to change engine). Does not mean higher affinity drug give more response- affinity is binding, response is how you change shape of receptor after bind.
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted.
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted. Most-seen graph in pharmacology? (DE or dose response curve). Can you tell the Kd ? No!!
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Now effect- not binding (lab science)- in ward interested in effect, so from here canāt tell Kd or affinity.
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted. Most-seen graph in pharmacology? (DE or dose response curve). Can you tell the Kd ? No!!
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Now effect- not binding (lab science)- in ward interested in effect, so from here canāt tell Kd or affinity.
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted. Most-seen graph in pharmacology? (DE or dose response curve). Can you tell the Kd ? No!!
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Now effect- not binding (lab science)- in ward interested in effect, so from here canāt tell Kd or affinity.
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted. Most-seen graph in pharmacology? (DE or dose response curve). Can you tell the Kd ? No!!
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc
Now effect- not binding (lab science)- in ward interested in effect, so from here canāt tell Kd or affinity.
I like to call dose
Most useful graph to compare different drugs. Most impt graph type in pharmacology.
Dose is on log scale. Just plot on this scale give you log value, no need take log and antilog. Scale is log: see the exponential increase.
Name of shape: sigmoidal not rect hyperbola
Most useful graph to compare different drugs. Most impt graph type in pharmacology.
Dose is on log scale. Just plot on this scale give you log value, no need take log and antilog. Scale is log: see the exponential increase.
Name of shape: sigmoidal not rect hyperbola
The units of EC50 and [D] are concentration, but log[D] is unitless.Ā
Most useful graph to compare different drugs. Most impt graph type in pharmacology.
Dose is on log scale. Just plot on this scale give you log value, no need take log and antilog. Scale is log: see the exponential increase.
Name of shape: sigmoidal not rect hyperbola
Most useful graph to compare different drugs. Most impt graph type in pharmacology. We are INTERESTED IN WHAT THE DRUG CAN DO IN THE RANGE OF 20-80% OF MAX EFFECT. OTHER SECTION LESS RELEVANT.
Small dose not compressed together, large dose not flat plateau
Linear middle segment
Most useful graph to compare different drugs. Most impt graph type in pharmacology. We are INTERESTED IN WHAT THE DRUG CAN DO IN THE RANGE OF 20-80% OF MAX EFFECT. OTHER SECTION LESS RELEVANT.
Small dose not compressed together, large dose not flat plateau
Linear middle segment
Most useful graph to compare different drugs. Most impt graph type in pharmacology. We are INTERESTED IN WHAT THE DRUG CAN DO IN THE RANGE OF 20-80% OF MAX EFFECT. OTHER SECTION LESS RELEVANT.
Small dose not compressed together, large dose not flat plateau
Linear middle segment
Most useful graph to compare different drugs. Most impt graph type in pharmacology. We are INTERESTED IN WHAT THE DRUG CAN DO IN THE RANGE OF 20-80% OF MAX EFFECT. OTHER SECTION LESS RELEVANT.
Small dose not compressed together, large dose not flat plateau
Linear middle segment
Most useful graph to compare different drugs. Most impt graph type in pharmacology. We are INTERESTED IN WHAT THE DRUG CAN DO IN THE RANGE OF 20-80% OF MAX EFFECT. OTHER SECTION LESS RELEVANT.
Small dose not compressed together, large dose not flat plateau
Linear middle segment
Kd = EC50 if there is 1:1 relationship bet binding and effect. Usually: full effect with less than full binding- effect is left shifted.
or ED50
Notice Y axis is effect, not binding. Can be any effect measured eg heartbeat, muscle contraction, speed of running, cellular: release of calcium, etc