PHARMA REVIEWER

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.