mechanism of drug absorbtion

WELCOME TO ALL

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MECHANISMS OF DRUG ABSORPTION

DIPAK KUMAR DASHM.PHARM

PHARMACEUTICSHPI

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WHAT IS DRUG ABSORPTION ?

The process of movement of unchanged drug from the site of administration to systemic

circulation.

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INTRODUCTONThe majority of drug are administered extravascularly generally orallyThe drug can exerts their pharmacological action when they come in to blood circulation from their site of application, and for this absorption is an important stepDrug absorption is defined as the process of movement of unchanged drug from the site of administration to systemic circulation 4

PRINCIPAL MECHANISMS OF DRUG ABSORPTION

1. Passive diffusion2. Pore transport3. Carrier mediated transport4. Facilitated diffusion5. Active transport6. Electrochemical diffusion7. Ion-pair transport8. endocytosis

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Direction of diffusion always from higher to lower concentration.

SIMPLE DIFFUSION

equilibrium exchange of solute

down the gradient 6

PASSIVE DIFFUSION

Driving force is concentration gradient.

Down hill transport occur.Drug transfer directly proportional to concentration gradient across membrane.Greater membrane/water partition coefficient faster the absorption.

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FICKS FIRST LAW OF DIFFUSION

Which states that the drug molecules diffuse from a region of higher conc. to lower conc.

until equilibrium is attained. Sink condition.

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PORE TRANSPORTAbsorption of low molecular weight drug .

Driving force is hydrostatic pressure.Solvent drag.Permeation through water filled channel.

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CARRIER MEDIATED TRANSPORT

False nutrients.Transport process is structure specific.Limited carrier.Capacity limited.

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MIXED ORDER KINETICS

Here drug absorption increases with concentration until carrier become saturated after that it becomes constant value.FIRST ORDER+ZERO ORDER

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CARRIER MEDIATED TRANSPORT

FACILITATED DIFFUSION

ACTIVE TRANSPORT

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FACILITATED DIFFUSION

Operate down the concentration gradient.Faster than passive diffusion.No energy expenditure involved.Glucose transport occur.

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GLUCOSE TRANSPORT

Uses transport proteins Facilitated Diffusion to Equilibrium

Figure 5- 21: Diffusion stops at equilibrium (panoramic lower left 66%)

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ACTIVE TRANSPORT

cell uses energy

actively moves molecules to where they are needed

Movement from an area of low concentration to an area

of high concentration

(Low High)15

CARRIERSCarrier proteins used in active

transport include: -uniporters – move one

molecule at a time -symporters – move two

molecules in the same direction -antiporters – move two

molecules in opposite directions

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ELECTRO CHEMICAL DIFFUSION

Charge on the membrane influence the permeation of drug.Unionized molecule>anions>cationsWhen cations atached to negatively charged intracelular membrane then create electrical gradient.

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ION PAIR TRANSPORT

Drug penetrate the membrane by forming reversible neutral complex with endogenous ions of GIT like mucin.Example; sulfonic acid

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VESICULAR TRANSPORT

Transport large particles or fluid droplets through membrane in

vesiclesuses ATP

Exocytosis –transport out of cell Endocytosis –transport into cell

phagocytosis – engulfing large particles

pinocytosis – taking in fluid droplets

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PHAGOCYTOSIS

PHAGOCYTOSIS

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REFERENCES Milo Glibaldi Biopharmaceutics and

Clinical Pharmaceutics, Reprint 2006 , 4thEdn

published by Pharma book syndicate Hydrabad, page number 24-32

Robert E.Notari Biopharmaceutics and clinical Pharmaceutics, Second Indian

reprint 2008, CBS Publisher and distributors New Delhi, Page no. 22-44

Leon Shargel /Andrew B.C. YU. Biopharmaceutics and Pharmaceutics, 4th Edn 1999, Published by McGraw-Hill companies New York, page no. 99-108

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D.M. Brahmankar and Sunil B. Jaiswal, Biopharmaceutics and

Pharmacokinetics: A Treatise. 1995, 1st Edn, Published by M. K. Jain for

Vallabh Prakashan AP-53A, Pitampura, New Delhi-110034; Page numbers 5-

16.

THANK YOU

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