JINNAH UNIVERSITY FOR WOMEN PHARM-D RAMSHA TAREEN , SOHAIBA SOHAIL , MAHRUKH KHAN , IFRAH AHMED

3. • The relevant amount of an administered dose of the
particular drug that reaches the systemic circulation and
the rate at which this occurs is known as bioavailability.
• It is usually less than 1 and its value is usually given in
fraction.
• It is the fraction of drug that reaches systemic circulation
in an unchanged form for biological effect following
administration by any route .
• IV has 100% bioavailability.

6. • OESOPHAGUS :- when a drug is administered orally it
travel down through the esophagus because of its
peristaltic contraction waver of the upper and lower
sphincters and the related propulsive force which help
the gravity .
• here no absorption takes place.

7. • STOMACH
• Weakly acidic drug absorb good in stomach that is due to
The human stomach is capable of absorbing most acidic
drugs and the very weakly basic drugs. Salicylic acid,
aspirin, thiopental, etc. which are dissociated in the acidic
gastric contents, are readily absorbed. Phenol red,
quinine, etc. which are almost completely ionized in acid
solution are not absorbed.

8. • SMALL INTESTINE :-
• It has the largest surface area
• The greater the surface area the greater will be the
absorption and bioavailability of drug .
• Small intestine has large surface area due to following
reasons
 FOLDS OF KERECKRING.
 PRESENCE OF VILLI AND MICROVILLI.

10. • It is an important consideration in absorption of drug as
PH effects the absorption of drug in 2 ways
 Extent of ionization of the drug
 Chemical stability aspect of the drug
PH OF STOMACH

11. • Gastric ph. returns to lower fasted state in 2-3 hrs.
depending on size of the meal
• For example :- stomach has acidic PH so drug with
opposite PH will be IONIZED and SOLUBLITY of that
drug will be better
• But if the drug with same PH as that of stomach (taking
as a example) will come in UNIONIZED form and will be
ABSORBED better.
• Presence of food effects the absorption of drug as the
presence of foods delays the absorption of some drugs
such as TETRACYLNES,ACETAMINOPHEN etc.
• Whereas, on the other hand food may also increase the
absorption of few drugs e.g. lipid soluble drugs

12. • As ANTACID increases the ph. that is due to the fact that
they neutralize the acid in stomach and increases the PH
.

13. • BASIC drug absorbs better in SMALL INTESTINE
because the PH rises along the length of small intestine (
due to the presence of bicarbonates secreted by small
intestine ).
Presence of food
stimulates the flow
of bile which
contain bile acids
ACT AS A
SURFACTANTS
Involved in
solubilization of fats
and hydrophobic
drugs.

14. • The ph. drops up to 6.5 in colon due to :-
Bacterial
enzymes
breakdown
undigested
carbohydrates
Convert them
into short
chain fatty
acids
Lowers the PH

16. • Gastrointestinal (GI) motility refers to the movement of
food from the mouth through the pharynx (throat),
esophagus, stomach, small and large intestines and out
of the body.
• That is for the drugs that are given orally.
• With in the GI tract drug movement depends on whether
alimentary canal is in FED state or is In FASTED state.

17. • Gastric and small intestinal myoelectric and motor activity is
divided into two main patterns,
• During fasting, the predominant pattern of activity is the
migrating myoelectric complex (MMC), a cyclically occurring
pattern of electric and mechanical activity that is initiated in the
stomach and duodenum almost simultaneously and, from
there, propagates the length of the small intestine.
• The physiologic role of the MMC is to clear the stomach and
small intestine of residual food, secretions, and desquamated
cells and propel them to the colon. It basically empties the
upper GIT to the cecum.
FASTED
STATE
FED
STATE

19. PHASE 3
INTENSE CONTRACTION
Contraction with higher amplitude, push
the residual content down to the
alimentary canal
Duration : 5-15 mins
PHASE 2
IRREGULAR PHASE
Increased number of contraction that are
irregular
Duration : 20-40 mins
PHASE 1
Calm phase
Inactive period ( alimentary canal is
quiescent)
Duration : 30-60 mins

20. PHASE 4
Reduction of contraction
leading to PHASE 1 DURATION “ 0-5 mins
FED STATE :- two activities has been observed in FED
STATE
1.

21. • 2. peristalsis
Contraction of
distal
stomach
Mix and
breakdown
food particles
Move them
towards
pyloric
sphincter

22. • Composition of food.
• Postural position.
• Effect of drugs.
• Effect of disease state.
• Emotional state of a person.
• exercise.

24. • The enzymes present in the gastric juice are called as
luminal enzymes
• following are the luminal enzymes:-
Lipases
Amylases
Proteases
pepsin
They are responsible for nutrient digestion.

25. • Azulfidine , a pro drug of 5-aminosalicylic acid linked via
an AZO bond to sulfapyridine
• Sulfapyridine moiety makes the drug too large and
hydrophilic to be absorbed in the upper GIT and this
permits its transport intact to the colonic region.
• The bacterial enzymes reduce the AZO bond and release
the active drug 5 amino salicylic acid for local
inflammatory bowel disease.

27. PROPULSIVE MOVEMENT
• it is known as up and
down movement
• Causes crushing of
dosage form.
• Determine intestinal
transit rate and residence
time of drug.
MIXING MOVEMENT
• It is known as
segmentation movement.
• It causes movement of
drug which is in solution
form to the GI membrane.
• It facilitates dissolution of
drug.

28. • Drugs that dissolve slowly in Small intestine and absorb
here, if intestinal motility is increased ,
• Drugs that are absorbed by intestinal carrier mediated
transport system for them motility is very important .
• Enteric coated dosage form which release drug only
when they reach the small intestine.
Drug rapidly
MOVES in SI
Abs is
decreased
BIOAVALIA
BLITY IS
DECREAS
ED

29. • Thickness of diffusion layer “h”
• A/c to NOYES WHITNEY equation
• As, H is effected by
 Viscosity of FLUID
 Motility of GIT
High motility the “H” will be reduced and
Dissolution will be increased that will
Ultimately increase the Bioavailability