Presented By

Farzana Sultana

Raziya Sultana

Tahmina

Kaniz Fatema

Nazmus Sakib

Is the passage of drug from its site of

administration to its site of action through cell

membranes.

Drug orally given

GIT

Disintegration (to form granules ) into small molecules

Dissolution into the aqueous media

Absorption

Since oral route of drug administration is most

common for systemically acting drug and through

this route drugs mostly absorbed from GIT so here

we will discuss on oral administration of drug.

1. Passive diffusion

2. Carrier- mediated transport:

a) .Active diffusion

b). Facilitated diffusion

3. Pore Transport

4. Ionic or Electrochemical diffusion

5. Ion-pair transport

6. Endocytosis

The passage of drug

molecules occurring from

the side of high drug

concentration to low drug

concentration

x

CCDAk

dt

dQ lh )(

Q: is the net quantity of drug transferred across

the membrane, t: is the time

Ch: is the conc on one side (GIT) and Cl:

that on the other side (plasma)

x: is the thickness of the membrane

A: is surface area of membrane and D: is

the diffusion coefficient related to permeability

k: is the partition coefficient of the drug

Active Transport

The drug is transported against a concentration gradient .This

system is an ENERGY consuming system.

Example: Glucose and Amino acids transport.

A drug carrier is Required but no ENERGY is

necessary. e.g. vitamin B12 transport. Drug moves

along conc gradient (from high to low), downhill

but faster .

Pore Transport: In this process low mol. Wt. (less than 100) molecules passes the membrane by osmotic pressure.

Ion Pair Transports: Here the cationic drugs or anionic drugs penetrates the membranes by forming reversible neutral complexes. Such phenomena is called ion pair transport.

Endocytosis: It is a minor transport mechanism which involves engulfing extracellular materials with in a segment of cell membrane to form a vesicles which then pinched off intra cellularly.

Factors Related to Drugs :

1.Lipid water solubility:

Lipid soluble drug… absorption Water soluble drug… absorption

2. Molecular size:

Smaller mol. Size….rapid absorption large mol. Size… absorption

3. Particle size:

Large particle size… slower absorption small particle size… absorption

4. Degree of Ionization:

Acidic drug unionized….. Better absorption from acidic compartment

5. Physical Forms :

Solutions>Emulsions>Suspensions>Capsules> Tablets> Coated Tablets>Enteric

Coated Tablet>Sustain Release Tablet

6. Chemical Nature: Salt form of drug > organic compound

inorganic form > organic compound

7. Dosage Forms :

Rapid disintegration ……rapid absorption

Rapid dissolution…….. absorption

Factors Related to Body

1. Area of Absorptive Surface : stomach < intestine

2. Blood supply :

in which part blood supply is greater there absorption rate is high.

3. pH :

Acidic pH favors acidic drug absorption while basic pH is better for basic drugs.

4. Presence of other Substances :

Iron given with milk ……… absorption

Vitamin C…….. Absorption of iron

5. Motility of drug :

Drugs are better absorbed in normal GIT movement

6. Functional Integrity of Absorptive Surface :

Flattening and edema of mucosa……. Absorption

7. Diseases :

Diarrhea…. Absorption

Malabsorptive syndrome ……. absorption

Convenient - can be self- administered, pain free, easy to

take

Absorption - takes place along the whole length of the GI

tract

Inexpensive - compared to most other parenteral routes

vomiting/stomach distress

variability in dose

effect too slow for emergencies

unpleasant taste of some drugs

unable to use in unconscious patient

first pass metabolism