1

FACTORS AFFECTING DRUG ABSORPTION

Name: Deepak.S.PandeyM.Pharm (Ist year)

Advanced Pharmaceutics.Parul university

2

LIST OF CONTENTS:• INTRODUCTION OF ABSORPTION• TRANSPORT PROCESS• FACTORS AFFECTING DRUG ABSORPTION: 1)Physiological factors 2)physiochemical factors 3)pharmaceutical factors• REFERENCES

3

ABSORPTION:• Definition: The process of movement of

unchanged drug from the site of administration to systemic circulation.

4

CELL MEMBRANE:• Cell membrane mainly consists of: 1) Lipid bilayer:- -phospholipid -Cholesterol -Glycolipids 2) Proteins:- -Integral membrane proteins -Lipid anchored proteins -Peripheral Proteins

5

TRANSPORT PROCESS:

• PASSIVE DIFFUSION• PORE TRANSPORT• FACILITATED DIFFUSION• ACTIVE TRANSPORT• PINOCYTOSIS

6

1.PHYSIOLOGICAL FACTORS:

• AGE• GASTRIC EMPTYING• INTESTINAL TRANSIT• GASTRO INTESTINAL PH• DISEASE STATE• GASTRO INTESTINAL CONTENTS• PRESYSTEMIC METABOLISM.

7

AGE:

• In children & Infants Gastric pH is high and intestinal surface and flow to git is low.

• while in adults altered gastric emptying, decrease intestinal surface area, decrease gastric blood flow & higher incidence of achlorhydria cause impaired drug absorption.

8

Gastric emptying:

• Gastric emptying is the passage of drug from stomach to small intestine.

• Gastric emptying is delayed when co-administered with food.

• Factors that influence G.E are :volume of meal, composition of meal, physical state and viscosity of meal, temperature of meal, body posture, exercise ,disease state etc.

9

Intestinal transit time:

• Since, intestine is the major site of absorption of most of the drugs, Long intestinal transit time is desirable for the complete absorption of drugs.

• Delayed intestinal transit is desirable for : --Drugs that dissolve only in intestine (enteric coated ). --Drugs absorbed from specific sites in the intestine.

10

Gastro intestinal PH:

• A difference in PH is observed between gastric and colon fluids. The GI PH increases gradually from stomach to the colon and rectum.

• The PH of GI fluids influence the drug absorption in several ways:

-dissolution -stability.

11

DISEASE STATE:

• GI Disease: Infection such as Achlorhydria, malabsorption and surgeries such as gastrectomy affect the absorption of drugs to a greater extent.

• Disorders such as hepatic cirrhosis influence bio-availability mainly of drugs that undergo considerable first-pass hepatic metabolism e.g. Propranolol

12

Presystemic metabolism:

The main reason for the decrease in bioavailability of a drug are decreased absorbtion or first pass metabolism. various enzyme that affect presystemic meatbolism of drugs are : -gutwall enzyme -hepatic enzyme -bacterial enzyme.

13

2)Physicochemical factors:

• DRUG SOLUBILITY & DISSOLUTION RATE.• PARTICLE SIZE• POLYMORPHISM &AMORPHISM• PSEUDOPOLYMORPHISM• SALT FORM OF THE DRUG• Pka OF THE DRUG

14

Particle size:

The absorption of the drug can be increased by increasing the particle surface area by micronization.

Smaller the drug particle

Greater the surface area

15

Polymorphism and amorphism:

• When substance exists in different crystallineforms it is polymorphism.

16

AMORPHISM:

• They have greater aqueous solubility than the crystalline forms because the energy required to transfer a molecule from crystal lattice is greater than that required for the non crystalline solid.

• Eg:Novobiocin• The order of Dissolution & hence Absorption for

different solid dosage forms is amorphous > meta-stable > stable.

17

PH PARTITION HYPOTHESIS:

UNIONISED DRUG HIGH ABSORPTION

IONISED DRUG LOW ABSORPTION

18

SALT FORMATION OF A DRUG:

• Salt of weak acid and weak bases have much higher aqueous solubility than the free acid or base.• Therefore, if the drug can be given as a salt, the solubility can be increased & the dissolution can be improved.

19

3)Pharmaceutical factors:

• MANUFACTURING VARIABLES: -Method of granulation -Compression force.• NATURE AND TYPE OF DOSAGE FORM.• PHARMACEUTICAL INGREDIENT AND

EXCIPIENTS.• STORAGE CONDITIONS.

20

Manufacturing variables:

1) Method of granulation: The method of dry granulation can be used to produce tablets that dissolve at a faster rate. 2) compression force: Influence the hardness, density,porosity,disintegration,dissolution of tablet.

21

Nature and type of dosage form:

• Bioavaibility of a drug from various dosage form is in the following order:

• solution>emulsion>suspension>Capsules>tablets>coated tablets>enteric coated tablet>sustained release tablet

22

• Pharmaceutical excipients.

• Product storage condition.

23

REFERENCE:

• TEXTBOOK OF BIOPHARMACEUTICS AND PHARMACOKINETICS,BY D.M.BRAHMANKAR And SUNIL .B. JAISWAL,

PG.NO.5-97.

24

•Thank you.