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invito release models.pptx
- 1.
- 2. Drug releaseis the process by which a drug leaves a drug product and is subjected to absorption, distribution, metabolism, and excretion (ADME), eventually becoming available for pharmacological action. Examples: Modified release Controlled release Delayed release drug products Extended release drug products.
- 3. In vitrodrug release has been recognized as an important element in drug development. Under certain conditions it can be used as a surrogate for assessment of bioequivalence.
- 4. Several theories/kineticsmodels describe drug release from immediate and modified release dosage forms. There are several models to represent the drug release profiles as a function of t (time) related to the amount of drug dissolved from the pharmaceutical dosage system.
- 5. The quantitativeinterpretation of the values obtained in the assay is facilitated by the usage of a generic equation It mathematically translates the release curve as the function of some other parameters related with the pharmaceutical dosage forms.
- 6. Equation canbe deduced by a theoretical analysis of the process. For example zero order kinetics.
- 7. Zero orderrelease model First order release model Korsmeyer model. Hixson–Crowell Higuchi model etc
- 8. Dissolution time(tx %) Assay time (tx min ) Dissolution efficacy (ED) Difference factor ( f1 ) Similarity factor ( f 2 )
- 9. Zero orderrelease kinetics refers to the process of constant drug release from a drug delivery device .i.e. Oral osmotic tablets Transdermal systems Matrix tablets Low-soluble drugs etc.
- 10. Drug dissolutionfrom pharmaceutical dosage forms that do not disaggregate and release the drug slowly . Assuming that area does not change and no equilibrium conditions are obtained. It can be represented as Q = Q0 + Kot or Wo - Wt = Kt
- 11. W0 – Wt= Kt or Q = Q0 + K0t where W 0 or Q0 is the initial amount of drug in the pharmaceutical dosage form. Wt or Q is the amount of drug in the pharmaceutical dosage form at time t K is a proportionality constant.
- 12. Dividing thisequation by W0 and simplifying W0 – Wt = K0t W0 W0 ft = 1- (Wt /W0) and ft represents fraction of drug dissolved in time t ft = K0 t
- 13. In thisway, graph of the drug-released fraction versus time will be linear.
- 14. The applicationof this model to drug dissolution studies was first proposed by Feldman (1967) and later by Wagner (1969) This model has been used to describe absorption and elimination of drugs. It is difficult to conceptualize this mechanism in a theoretical basis.
- 15. The dissolutionphenomena of a solid particle in a liquid media implies a surface action, as can be seen by the Whitney Equation.
- 16. The dissolutionphenomena of a solid particle in a liquid media implies a surface action, as can be seen by the Whitney Equation C is the concentration of the solute in time t, Cs is solubility in equilibrium K is a first order proportionality constant dC/dt =K (C s-C )
- 17. This equationwas altered by Brunner to incorporate the value of the solid area accessible to dissolution, S. Using the Fick first law, it is possible to establish the following relation for K1 dC/dt =K1 S (C s-C ) K1 = D Vh
- 18. Equation isobtained from Whitneys equation by multiplying both terms of equation by V and making k = k V 1 Comparing these terms, the following relation is obtained K = 𝑫 𝒉
- 19. Crowell adaptedtheWhitney Equation by combining all the previous equations it can be written as : where k = k1 S. 𝒅𝑾 𝒅𝒕 = 𝑲𝑺 𝑽 (VCs –W) = k (VCs –W )
- 20. If onedosage form with constant area is studied in ideal conditions. It is possible to use this last equation that after integration, equation become W = VCs ( 1 - 𝒆−𝒌𝒕 )
- 21. W = VCs( 1 - 𝒆−𝒌𝒕 ) This equation can be transformed, by applying decimal logarithm to this equation it gives log ( VCs – W) = log VCs - 𝒌𝒕 𝟐.𝟑𝟎𝟑
- 22. The following relationcan also express this model Qt = Q0 + K0t Qt= Q0 𝒆−𝒌𝒕 ) Qt is the amount of drug released in time t, Q 0 is the initial amount of drug in the solution K 1 is the first order constant. log Qt= log Q0 + 𝒌𝒕 𝟐.𝟑𝟎𝟑
- 23. The pharmaceuticaldosage forms following this dissolution profile, such as those containing water-soluble drugs in porous matrices release the drug in a way that is proportional to the amount of drug remaining.