Pharmacology I 8/20/25

pharmokinetics

body’s affect on the drug over time

5 basic parameters

1. absorption

2. distribution

3. metabolism

4. excretion

5. half-life

pharmacodynamics

drugs effect on the body

pharmacotherapeutics

application of drugs for the treatment and management of diseases

bound drugs

the body will try to achieve an equilibrium, it will become unbound → excreted

free drug

1. can be metabolized → excreted

2. can have an active metabolite that can also get excreted

3. goes to the site of action or stored in tissues

drug process

1. absorption (if taken orally, for ex)

2. distributed

3. metabolism

4. elimination

lag period

where there isn’t enough medication to produce an affect

minimum effective concentration (MEC)

the onset of drug’s effect (when it starts working, and the beginning of the duration of action)

therapeutic window

between the minimum effective concentration (MEC) for desired response and adverse response

duration of action

length of time the drug produces its therapeutic effect

from the onset of effect → peak effect → the point where it reaches the MEC for desired response again

formulation of drugs

dependent on

1. barriers drug needs to pass

2. setting med is administered

3. urgency of the need for med

4. stability of the drug

5. first pass effect

first pass effect

the process where a medication goes through when its taken orally, it’s metabolized typically in liver first before the bloodstream

→ medication can lose potency/effectiveness due to this

routes of drug administeration

1. po: oral

2. iv: intravenous

3. im: intramuscular

4. sc: subcutanenous

(all except PO are parenteral)

parental administration

any routes of administration that do NOT involve drug absorption via the GI tract (IV, intramuscular, subcutaneous, and transdermal routes)

oral

absorption pattern: variable

advantages: safest and common, convenient, economical

disadvantages: limited absorption of drugs, food can affect, depends on patient compliance, drugs may be metabolized before absorption

intravenous (IV)

absorption not required

advantages: immediate effects, ideal if dose is high volume, good for emergency

disadvantages: inaccessible unless in clinical setting, must be slowly injected

subcutaneous

absorption pattern: depends on drug diluents. aqueous solution is fast, but depot preparation is slow

advantages: good for slow release

disadvantages: drug can be irritation, not good for large volumes

intramuscular

absorption pattern: aqueous solution is fast, depot preparation is slow

advantages: good for moderate amount

disadvantages: can be painful, can cause ___ hemorrhage

DO RECTAL, INHALATION, SUBLINGUAL PG 14

drug absorption

influenced by

1. route of administration

2. blood flow

3. surface area available

4. solubility

5. drug-drug interactions

6. pH

7. drug concentration (sometimes)

transdermal

absorption pattern: slow and sustained

advantages: bypasses first-pass effect, convenient, good for lipophilic drugs, ideal for drugs quickly eliminated by body

disadvantages: patient allergies, drug must be highly lipophilic, small daily doses

passive diffusion

molecules move down to the concentration gradient

facilitated diffusion

carrier proteins allow drug molecules to piggy-back through the membrane

can become saturated

can be inhibited by competitive compounds

active transport

energy dependent

specific carrier proteins can move drug molecules against concentration gradient

can become saturated

may be competitively inhibited by other cotransported substances

endocytosis

used for large molecules

the membrane engulfs the molecule and then pinches off the drug filled vesicles

passive diffusion

1. no cellular energy used

2. drugs move from high → low concentration

3. stops when concentration is equal

active transport

1. requires energy from hydrolysis of ATP to move drugs across membrane

2. drugs move against concentration gradient

3. drugs are structurally similar to naturally occurring metabolites may need this

slow absorption

oral, IM, subcutaneously

fast absorption

IV, inhalation, sublingual

increased blood flow

increased absorption

decreased surface area

decreased absorption

drug distribution

process where drug leaves the bloodstream and enters the interstitium of tissue’s cells

• depends on

  • ability to permeate capillaries

  • vascularity of tissues

  • ability to bind to plasma proteins/tissue protein

  • fat or water soluble characteristics

  • drug dissolution

  • GI tract environment

volume of distribution

amount of drug in the body related to plasma concentration

heart, liver, kidneys

drugs are distributed to _____ ____ ___

skin, muscle, fat

drugs distribute slow to ____ ___ ___

lipid soluble

_____ drugs easily cross through cell membranes including blood brain barrier

water soluble

____ drugs can NOT pass easily through cell membranes

blood-brain barrier

diffusion barrier, which impedes influx of most compounds from blood to brain

• ionized molecules can’t enter brain due to structural modifications

• non-ionized molecules not bound to plasma proteins can enter brain because they are lipid soluble

liver

• enzymes responsible for most oxidative reactions of drugs are in cytochrome p450 system

  • concentration of blood in bloodstream lowered by first-pass effect and induction/inhibition of drug metabolism

cytochromes p450 (CYPs)

constitute the major enzyme family capable of catalyzing the oxidative biotransformation of most drugs

primary metabolism sites

liver, kidney, biliary tract

prodrug

an inactive/less active drug is “metabolized” into a more active drug

(and an active drug can “metabolize” to less active one)

drug elimination

1. excretion: removal of waste substances from body fluids

2. kidney excretion (glomerular filtration, proximal tubular secretion, etc)

3. clearance: rate of elimination of substances from blood

4. renal clearance: total amount of drug excreted over time

creatinine clearance (crcl)

indicator for GFR (glomerular filtration rate) and renal function

creatinine

comes from skeletal muscle creatine phosphate

most people form same amount everyday

factors influence CrCl

• gender

• age

• weight

• height

• serum creatinine

half-life

• time for a drug CONCENTRATION to fall to one half of its original concentration

• measure of how long it takes for half of the drug to disappear from bloodstream

• helps determine dosing intervals and “steady state”

six half-life rule

for the concentration of a med to reach a point where it stops causing any effects (basically once it reaches 6 half lives, the med is as good as gone)

onset of action

time interval between time the drug is administered and when the therapeutic effect begins

peak

CONCENTRATION when absorption rate and elimination rate are at equilibrium. not necessarily the peak therapeutic response

drug bioavailability

• ability of drug to reach systemic circulation after oral dosage

• good indication that amt of med is absorbed

• drugs with low oral bioavailability are poorly absorbed in GI tract or partially metabolized by liver