PHARMACODYNAMICS

1. PHARMACODYNAMICS

2. PHARMACOLOGY
Pharmacology is the science of drugs .
Drug: “ A drug is any chemical molecule, which can be administered exogenously
into the living system produce biological response or effect.”
PHARMACOLOGY
PHARMACOKINETICS
Kinesis meaning movement
- What the body does to the drug
PHARMACODYNAMICS
Dynamics meaning action / power
- What the drug does to the body

3. Pharmacodynamics is the study of drug effects.
• It describes, what the drugs do and how they do.
“what the drug does to the body when they enter”
• Drugs (except those gene based) do not impart new functions to any
system, organ or cell; they only alter the pace of ongoing activity.
Example : Adrenaline reacts with adrenoreceptors and ultimately leads to
cardiac stimulations .
PHARMACODYNAMICS

4. PRINCIPLES OF DRUG ACTION
Stimulation
Depression
Irritation
Replacement
Cytotoxic action

5. STIMULATION
DEPRESSION
Enhancement of the levels of activity of specializes cells . Eg : Adrenaline
stimulates heart . However , excessive stimulation is often followed by
depression of that function .
Eg : Picrotoxin , a CNS stimulant , produces convulsions followed by coma and
respiratory depression on high doses .
Selective diminution of activity of specialized cells .
Eg : barbiturates depress CNS , quinidine depress heart . Some drugs stimulate
one type of cells but depress the other
Eg: Ach ( acetylcholine ) stimualtes intestinal smooth muscles but depress SA
node in heart .

6. IRRITATION
REPLACEMENT
Non selective and noxious effect
Eg : counterirritant such as heat or an ointment increases blood flow to the
site , but strong irritants can cause inflammation and even necrosis .
Use of natural metabolites , hormones in deficiency state .
Eg : levodopa in Parkinsons , insulin in diabetes and iron in anemia .
Selective cytotoxic action for invading parasite or cancer cells , attenvating them
without significantly affecting the host cells .
Eg : penicillin , chloroquine , zidovudine , cyclophosphamide
CYTOTOXIC ACTION

7. MECHANISM OF DRUG ACTION
● ENZYMES
● ION CHANNELS
● TRANSPORTERS
● RECEPTORS
● A drug can bring about physical or chemical change in cell environment .
eg : stool softners ( MgOH ) that act by altering surface tension .
● Majority of drug produce their effects by
interacting with target biomolecules.
ie.proteins

8. ENZYMES
• Enzymes are protein molecules that
accelerates chemical reactions .
• Almost all biological reactions are carried out
by enzymes.
• Drugs can either increase or decrease the
rate of enzymatically mediated reactions.
Eg : captopril inhibits ACE ( angiotensin
converting enzyme )

9. IONS CHANNELS
● There are many ion channels in our
body which helps transmembrane
signaling and regulate intracellular
ionic composition .
● Eg ; Na , K channel , Ca channel
● Drugs can affect ion channels .
● Drugs can also affect ion movement
by directly binding on channel .
● Eg : quinidine blocks myocardial Na+
channel .

10. TRANSPORTERS
● Several substrates are move across
membrane by binding to specific
transporter .
● Many drugs affect this , they interact
with carrier and inhibit the movement of
metabolite/ ion .
Eg : amphetamines selectively block
dopamine reuptake in brain neurons by
dopamine transporters .

11. RECEPTORS
● Receptors are proteins or binding sites
which present on surface and inside the
cells , drugs bind with it , activate it and
give its pharmacological response .
 AGONIST – an agent which activate
receptors to produce effects .
Eg : opioids
 ANTAGONIST – an agent which inhibit
the action of agonist .
Eg : naloxone

12. THANK YOU !!