The document summarizes key concepts in pharmacology including: 1) Pharmacodynamics is the study of how drugs act on the body by mimicking chemical messengers. Dose-response relationships describe the body's response to varying drug concentrations. 2) Pharmacokinetics describes the movement of drugs through the body via processes of liberation, absorption, distribution, metabolism and excretion (LADME). 3) Drug effects can be primary (intended) or secondary (side effects), and their onset and duration depends on route of administration (rapid for IV, delayed for oral). Drug interactions can have additive, synergistic, antagonistic or potentiating effects.

1. Week 2 (Pharma)
Pharmacodynamics
- is the study of the effect of drugs on the
body.
- Drugs act within the body to mimic the
actions of the body’s own chemical
messengers.
Dose-Response Relationship
› is the body’s physiological response to
changes in drug concentration at the
site of action.
› Potency – refers to the amount of drug
needed to elicit a specific physiologic
response to a drug.
- How much drug to experience relief
› Efficacy – magnitude of effect a drug
can cause when exerting its maximal
effect. How effective the drugs.
› Maximal efficacy – the point at which
increasing a drug dosage no longer
increases the desired therapeutic
response. e.g., if the drug is not
effective, change the drug. Do not
increase the dosage.
Parameters of Drug Action
› Therapeutic Index – (TI) describes the
relationship between the therapeutic
dose of a drug (ED50) and the toxic
dose of a drug (TD50)
› Therapeutic dose of a drug (ED50) – is
the dose of a drug that produces a
therapeutic response in 50% of the
population.
› Toxic dose of a drug (TD50) – is the
dose that produces a toxic response in
50% of the population.
Example: 1000 paracetamol is still
acceptable, more than that dosage is not.
Every 4-6 hours.
› If the ED50 and TD50 are close- drugs
have a narrow therapeutic index. It
requires close monitoring to ensure
patient safety.
› Onset – is the time it takes for a drug to
reach the minimum effective
concentration (MEC) after
administration. period you take
medication.
› Time from drug administration to first
observable effect (T0-T1)
› Peak – occurs when it reaches its
highest concentration in the
blood/plasma concentration. T0-T2
- Free from the pain. You feel best not
better. Less or no more symptoms.
› Duration of action – is the length of
time the drug exerts a therapeutic
effect.
Therapeutic Drug Monitoring
› Drug concentration can be determined
by measuring peak and trough drug

2. levels. For specialized type of drug:
antibiotics, vancomycin (for infection
develop resistance that needed level up
or potent medication.)
› peak – highest plasma concentration.
30 minutes after infusion.
› trough – lowest plasma concentration.
30 minutes prior to the next infusion.
Importance of P and T
- To know when the next dose will drug
will be next administer.
Theories of Drug Action
A. Drug-Receptor Interaction
› Certain portion of drug molecule (active
site) selectively combines with some
molecular structure (reactive site) on
the cell to produce a biologic effect
› Receptor site- drugs act at specific areas
on cell membranes; react with certain
chemicals to cause an effect within the
cell
› “Lock and Key Theory”- specific
chemical (key) approaches a cell
membrane and finds fit (the lock) at
receptor site- affects enzyme system
within cell- produce certain effects.
› Drug + Receptor=Effect
B. Drug-Enzyme Interaction
› Interferes with enzyme systems that act
as catalyst from various chemical
reactions
› If single step in one of enzyme system is
blocked = normal function is disrupted
› No receptor site.
C. Nonspecific Drug Interaction
› Act by biophysical means that do not
affect cellular/enzymatic reactions.
› drugs do not bind to receptors but
instead saturate the water or lipid part
of a cell- drug actions occur based on
the degree of saturation.
› Neutralization of stomach acid by
antacids (tinutunaw ang hydrochloric
secretion in the body.)
D. Selective Toxicity
› Specific action on cellular structures
that are unique to the microbe.
› All chemotherapeutic agents would act
only in one enzyme system needed for
life of a pathogen or neoplastic cell.
› It is essential to the pathogen but not to
the host.
› One enzyme only is affected and not as
a whole.
Drug Response
1.Primary- always desirable/ expected and
physiologic effects
Glutathione- Detoxify the liver which whitens
the skin.
2.Secondary- desirable or undesirable

3. › Example: Diphenhydramine generic
name (Benadryl) brand name for rhinitis
› Primary effect: antihistamine; treat
symptoms of allergy
› Secondary: Drowsiness
Classification of Drug Action
1.Rapid- few seconds to minutes
› - IV, SL (sub-lingual, under the tongue),
Inhalations
2. Intermediate- 1-2 hours after administration
› - IM, SC
3. Delayed/Slow- several hours after
administration
› - Oral, rectal
Categories of Drug Action
1.Stimulation/Depression
› Stimulation- increased rate of cell
activity/ secretion from the gland. E.g.,
T3/T4 for hypothyroidism
› Depression- decreased cell activity and
function of a specific organ. E.g., Iodine,
propylthiouracil
2. Replacement- replaces essential body
compounds
› Example: Insulin
› Type 1 DM: absence of insulin and beta
cells. Inborn error. Insulin replacement
needed for actual hormone.
› Type 2 DM: is not genetic. Faulty
lifestyle habit. Middle-aged individual.
Can be corrected by diet lifestyle.
› GDM (gestational diabetes mellitus) –
occur during pregnancy of women. Too
old to be pregnant and physique.
3. Inhibition/Killing of Organism
› Interfere with bacterial cell growth
› Example: Antibiotics (kills bacteria)
4. Irritation
› Example: Laxative (constipation)-
irritate the inner wall of colon or lower
GI tract---increased peristalsis---
increased defecation.
Drug-Drug Interaction
1.Additive Effect-2 drugs with similar actions
are taken for a doubled effect
› 1+1=2
› Ibuprofen + paracetamol= added
analgesic effect
› Codeine with acetaminophen = better
pain control
2. Synergistic- combined effect of 2 drugs is
greater than the sum of the effect of each drug
given alone; 1+1=3
› Aspirin = 30% analgesic effect
› codeine – 30% analgesic effect
› combination = 90% analgesic effect
3. Potentiation- a drug that has no effect
enhances the effects of the second drug
› 0+1=2
› Alcohol enhances the analgesic activity
of aspirin.
› Prozac + Zestril

4. 4. Antagonistic- one drug inhibits the effect of
another drug
› 1+1=0
› Tetracycline + antacid= decreased
absorption of tetracycline
Adverse Drug Effects
1.Side Effects
› Results from the pharmacologic effects
of the drug
› Most common as a result of lack of
specificity of action within the
therapeutic range.
2. Allergic Reactions
› Unpredictable adverse drug effects;
more serious
› Response to patient’s immunological
system to the presence of the drug
› Do not occur unless the patient has
been previously exposed to the agent/
chemical related compound
3. Idiosyncratic Reaction
› Occurs when the patient is first to the
drug
› Abnormal reactivity to the drug caused
by a genetic difference between the
patient and normal individual.
› a patient with G6PD deficiency will have
anemia by using antioxidants.
4. Toxicity
› The degree to which a drug can be
poisonous and thus harmful to the
human body.
5. Iatrogenic responses
› Unintentional responses as a result of
medical treatment
› Nephrotoxicity; ototoxicity
› Vitamin d and calcium is
PHARMACOKINETICS
› is the process of drug movement
throughout the body that is necessary
to achieve drug action.
› Processes: LADME
1. Liberation
2. Absorption
3. Distribution
4. Metabolism –biotransformation
5. Excretion – elimination
6. Liberation

5. › is the first step in the process by which
medication enters the body and
liberates the active ingredient that has
been administered.
– Three (3) steps:
› Disintegration
› Disaggregation
› Dissolution
› The characteristics of a medication's
excipient play a fundamental role in
creating a suitable environment for the
correct absorption of a drug.
› This can mean that the same dose of a
drug in different forms can have
different bioequivalence, as they yield
different plasma concentrations and
therefore have different therapeutic
effects.
ABSORPTION
› is the movement of the drug into the
bloodstream after administration.
› 80% of drugs are taken by mouth –
enteral.
› Movement of drug molecules from site
of administration to circulatory system
Movement of drug particles from GIT to body
fluids involve 3 processes:
1. Passive transport
› Diffusion – drugs move across the cell
membrane from an area of higher
concentration to one of lower
concentration.
2. Facilitated diffusion –Active transport
– requires a carrier such as enzyme or protein
to move the drug against a concentration
gradient. Energy is required.
3. Pinocytosis – is the process by which
cells carry a drug across their membrane by
engulfing the drug particles in a vesicle
DISTRIBUTION
› process by which drug becomes
available to body fluids and tissues.
› is the movement of the drug from the
circulation to body tissues
METABOLISM
Also known as biotransformation is the process
by which the body chemically changes drugs
into a form that can be excreted.
› First-pass effect or first-pass
metabolism
› GI tract --- intestinal lumen -- liver---
some drugs are metabolized to an
inactive form and excreted--- reduced
amount of active drug
› liver enzymes – cytochrome P450
system – convert drugs to metabolites.
› decreased drug metabolism rate will
result in excess drug accumulation that
can lead to toxicity.
› Drug half-life is the time it takes for the
amount of drug in the body to be
reduced by half.
Example:
› Ibuprofen has a half-life of about 2
hours.

6. › if the patient takes 200 mg, in 2 hours,
50% of the drug will be gone, leaving
100 mg.
› after 2 hours - 50 mg.
› after 2 hours – 25 mg
› after 2 hours – 12.5 mg
› after 2 hours – 6.25 mg
Factors affecting biotransformation
1. Genetic- some people metabolize drugs
rapidly, others more slowly
2. Physiologic
3. Liver disease- do not bombarded with
medication.
4. Infants- decreased rate of metabolism.
No antibiotics, yes to vitamins since the
organs are underdeveloped.
5. Elderlies- decreased liver size, blood
flow, enzyme production- slows
metabolism
6. Environment- cigarettes may affect the
rate of some drugs.
7. Stressful environment- prolonged
illness, surgery, illness.
EXCRETION – ELIMINATION
› removal of the drug from the body.
Drug is changed into inactive form and
excreted by the body.
Routes:
› Kidney- main organ for drug
elimination: leave the body through
urine
› Free or/unbound/water soluble drugs-
filtered in the kidney
› (+) kidney disease- dose must be
decreased.
› kidneys – main route of drug excretion
› bile, lungs, saliva, sweat and breast
milk.
› urine pH influences drug excretion.
› normal urine pH 4.6-8
› acidic urine promotes elimination of
weak base drugs.
› alkaline urine promotes elimination of
weak acid drugs.
› prerenal, intrarenal and postrenal
conditions.
Terminologies
L = Liberation, the release of the drug from its
dosage form.
A = Absorption, the movement of drugs from
the site of administration to the blood
circulation.
D = Distribution, the process by which drug
diffuses or is transferred from intravascular
space to extravascular space (body tissues).
M = Metabolism, the chemical conversion or
transformation of drugs into compounds which
are easier to eliminate.
E = Excretion, the elimination of unchanged
drug or metabolite from the body via renal,
biliary, or pulmonary processes.