Explanation: For orally administered drug, the two critically slower rate determining step is the rate of dissolution and the rate of drug permeation. Dissolution is the rate determining stem for poorly aqueous soluble drugs and hydrophobic drugs.

Explanation: Dissolution rate is defined as the amount of solid substrate that goes into solution under constant time under standard temperature, pH, solvent composition and constant surface area. It is a dynamic process. Drugs having poor aqueous solubility have less dissolution rate.

Explanation: The solubility of any orally administered drug should be between 1-2 mg/ml in the range of pH 2-8. The solubility becomes a great matter of concern if it is less than that. And if more than that the dosage must be carefully calculated.

Explanation: Fick’s law of diffusion states that drug molecules diffuse from higher concentration to lower concentration until equilibrium is reached. Theories of drug dissolution are Diffusion layer model or Fil theory, Danckwert’s model or Penetration or surface renewal theory, Interfacial barrier model or Double barrier theory.

Explanation: Diffusion layer model states that solution of a solid form a thin film or layer at the solid-liquid interface which is called as the stagnant film or diffusion layer which gets saturated with the drug. This step is rapid.

Explanation: According to the interfacial barrier model, an intermediate concentration exists at the interface which is a result of the solvation mechanism and is a function of solubility. Here in the equation G stands for dissolution rate per unit area, Ki stands for effective interfacial transport constant.

Explanation: Danckwert did not approve the existence of the stagnant layer and suggested that turbulence in the dissolution medium exists at the solid/liquid interface. Due to which the agitated fluid consists of a macroscopic mass of eddies or packets reach the solid-liquid interface due to the eddy currents, absorb the solute by diffusion and carry it to the bulk of the solution.

Explanation: An intermediate layer exist at the interface of the solid and liquid layers. This intermediate layer holds and intermediate concentration at the interface which results is solvation mechanism. The theory does not talk about any turbulence, or presence of solutes.

Explanation: To calculate the particle size decrease and change in the surface area of the dissolution Hixson and Crowell’s cubit root law of dissolution is followed, Wo1/3-W1/3=Kt, where, Wo stands for original mass of the drug, W stands for the mass of the drug remaining after time t, K stands for dissolution constant.

Explanation: The two critical slower rate-determining processes in the absorption of orally administered drugs are the rate of dissolution and rate of the solute or the drug permeation through the cell membrane or biomembrane.

Explanation: Absolute or intrinsic solubility is defined as the maximum amount of solute dissolved in a given solvent under standard conditions of temperature, pressure, and pH. It is a static property. Dissolution rate is the amount of a solid substance that dissolves into solution under given conditions.

Explanation: The Danckwert’s model is expressed by the equation, V dC/dt = dm/dt = A (Cs-Cb).√ γ D, where γ is the rate of surface renewal, m is the mass of solid dissolved. Cs concentration of the solute.

Explanation: The statement is true. According to the interfacial barrier model, each face of a crystal has a different interfacial barrier. This concept is given by G=Ki (Cs-Cb).