Ce diaporama a bien été signalé.
Le téléchargement de votre SlideShare est en cours. ×

Factors influencing drug absorption

Publicité
Publicité
Publicité
Publicité
Publicité
Publicité
Publicité
Publicité
Publicité
Publicité
Publicité
Publicité
Chargement dans…3
×

Consultez-les par la suite

1 sur 21 Publicité
Publicité

Plus De Contenu Connexe

Diaporamas pour vous (20)

Similaire à Factors influencing drug absorption (20)

Publicité

Factors influencing drug absorption

  1. 1. PRESENTED BY:- GUIDED BY:- TARUN POKHARIYAL Mr. AJAY KUMAR TIWARI M.PHARM.(1st SEM.) LECTURER DEPT. OF pharmaceutics JAIPUR NATIONAL UNIVERSITY JAIPUR DATE:-15 NOV.2011
  2. 2. (A). PHARMACEUTICAL FACTORS:- I. PHSICOCHEMICAL PROPERTIES OF DRUG:- 1. DRUG SOLUBILITY AND DISSOLUTION RATE Solid disintegration dissolution Drug in permeation Drug Solid dosag solution at across mem. in drug e form absorption the particles site body Maximum absorbable dose (MAD) is used to correlate drug absorption MAD= Ka Sgi Vgi tr Ka= intrinsic absorption rate constant Sgi=solubility of drug in GI fluid Vgi=volume of GI fluid present. tr= residence of drug in GI
  3. 3. BIOPHARMACEUTICS CLASSIFICATION SYSTEM:- CLASS I DRUG:- high solubility and high permeability eg. diltiazem CLASS II DRUG:-low solubility and high permeability eg.nifedipine. CLASS III DRUG:-high solubility and low permeability eg. Insulin. CLASS IV DRUG:-low solubility and low permeability eg. taxol
  4. 4. THEORIES OF DRUG DISSOLUTION:- DISSOLUTION IS THE MASS TRANSFER FROM SOLID SURFACE TO THE LIQUID PHASE. Theories:- 1.Diffusion layer model/film theory 2.danckwerts’s model/penetration theory 3.Interfacial barrier model/limited solvation theory
  5. 5.  DIFFUSION LAYER MODEL/ FILM THEORY:-
  6. 6.  The rate of dissolution is given by Noyes and Whitney: dc = k (Cs- Cb) Where, dt dc/dt= dissolution rate of the drug K= dissolution rate constant Cs= concentration of drug in stagnant layer Cb= concentration of drug in the bulk of the solution at time t
  7. 7. dC DAKw/o (Cs – Cb ) dt Vh Where, D= diffusion coefficient of drug. A= surface area of dissolving solid. Kw/o= water/oil partition coefficient of drug. V= volume of dissolution medium. h= thickness of stagnant layer. (Cs – Cb )= conc. gradient for diffusion of drug.
  8. 8.  This is first order dissolution rate process, for which the driving force is concentration gradient.  This is true for in-vitro dissolution which is characterized by non-sink conditions.  The in-vivo dissolution is rapid as sink conditions are maintained by absorption of drug in systemic circulation i.e. Cb=0 and rate of dissolution is maximum.
  9. 9.  Under sink conditions, if the volume and surface area of the solid are kept constant, then dC K dt This represents that the dissolution rate is constant under sink conditions and follows zero zero order dissolution order kinetics. under sink condition first order dissolution under non-sink condition Conc. of drug Time
  10. 10. Danckwert’s model/Penetration or surface renewal Theory :- Dankwert takes into account the eddies or packets that are present in the agitated fluid which reach the solid liquid interface, absorb the solute by diffusion and carry it into the bulk of solution. These packets get continuously replaced by new ones and expose to new solid surface each time, thus the theory is called as surface renewal theory.
  11. 11. III. Interfacial barrier model/Double barrier or Limited solvation theory :-  The concept of this theory is explained by following equation- G = Ki (Cs - Cb) Where, G = dissolution rate per unit area, Ki = effective interfacial transport constant.
  12. 12. 2. PARTICLE SIZE & EFFECTIVE SURFACE AREA OF DRUG:- TWO TYPES OF SURFACE AREA CAN BE DEFINED:- 1.ABSOLUTE SURFACE AREA 2.EFFECTIVE SURFACE AREA 3. POLYMORPHISM:- enantiotropic polymorph:-which can be reversibly change into another form by altering the temp.or pressure. Monotropic polymorph:-is the one which is unstable at all temp. and pressure.
  13. 13.  Internal structure of a compound  Crystalline noncrystalline Polymorph( Molecular single adduct molecule) Stocheometric enantiotropic Nonstochiometric complexes complexes Organic monotropic Hydrates solvates
  14. 14.  5. drug pka and lipophilicity and gi Ph (PH PARTITION HYPOTHESIS):- This theory states for those drug compound of molecular weight greater than 100 which primariliy transported across the biomembrane by passive diffusion. Most drugs are weak electrolyte(weak acid or base) If the pH of either side of membrane is different than the compartment whose pH favours greater ionisation of drug will contain greater amount of drug and only unionised fraction of drug if sufficiently lipid soluble can permeate the membrane passively until the conc. Ofunionised drug on either side of membrane become equal.
  15. 15.  6. DRUG STABILITY:-  Degredation of drug into inactive form.  Interaction with one or more different components 7. STERIOCHEMICAL NATURE OF THE DRUG:- DOSAGE FORM(PHARMACOTECHNICAL) FACTORS:- 1) DISINEGRATION TIME:- 2) DISSOLUTION TIME:- 3) MANUFACTURING VARIABLES:- *excipients and manufacturing process* EXCIPIENTS:-vehicle, diluents(filler), binder and granulating agents, disintegrants, lubricants, surfactants, viscosity imparters ,buffers, complexing agents, Colorants Crystal growth inhibitors.
  16. 16. MANUFACTURING VARIABLES:- *Method of granulation-wet granulation method is most conventional technique but limited. Most recent method is APOC(agglomerative phase of communition) *Compression force:- *Intensity of packing of capsule contents- 4.NATURE AND TYPE OF DOSAGE FORM 5.PRODUCT AGE AND STORAGE CONDITION
  17. 17.  PATIENT RELATED FACTORS:- 1. AGE- 2. GASTRIC EMPTYING:-the passage from stomach to small intastine. Gastric emptying is first order process  Gastric emptying rate:-is the speed at which the stomach content empty into intestine.  Gastric emptying time:-is the time required for gastric content to empty into small intestine.  Gastric emptying t1/2 is the time taken for half the stomach content to empty. FACTORS EFFECTING GASTRIC EMPTYING:-  VOLUME OF MEAL  COMPOSITION OF MEAL  PHYSICAL STATE AND VISCOSITY OF MEAL  TEMP. OF MEAL
  18. 18.  GI pH  Electrolyte and osmotic pressure  Body posture  Emotional state  Exercise  Disease state  Drug 3.INTESTINAL TRANSIT:-the passage of drug through intestine called as intestinal transit. 4.GIT Ph:- it influence absorption in various ways;-
  19. 19. a. Disintegration b. Dissolution c. Absorption d. Stability 5.Disease state :- a. GIT disease b. Cardiovascular disease c. Hepatic disease 6.BLOOD FLOW TO GIT:-
  20. 20. 7.GASTROINTESTINAL CONTENT:- 1. Food- drug interaction 2. Fluid volume 3. Interaction of drug with normal gi contents 4. Drug –drug interaction 8. PRESYSTEMIC METABOLISM:- The loss of drug through biotransformation by such eliminating organs during its passage to systemic circulation is called first pass metabolism. Three types of systems:- 1. Luminal enzyme (digestive and bacterial enzyme) 2. Gut wall enzyme 3. Hepatic enzyme

×