Test
MD4 How drugs dissolve
Este test tiene tipos de pregunta que se abren en el reproductor de siempre.
Preguntas del test (8)
1Pharmaceutical examples of release of drug (API) from dosage forms:
- release from conventional tablets that [blank_start]disintegrate[blank_end]
- release from normal capsules containing [blank_start]solid drug[blank_end]
- release from matrix tablets or pellets: lipid matrix ([blank_start]nonhydrating[blank_end]) and swellable ([blank_start]hydrating[blank_end]) matrix
- release from a coated tablet or coated granules/pellets, where the coat remains [blank_start]intact[blank_end]; liquid & dissolved drug may [blank_start]permeate[blank_end] the film coat- Adisintegrate
- Bsolid drug
- Cnonhydrating
- Dhydrating
- Eintact
- Fpermeate
2There are two steps of the dissolution of a solid dosage form:
1. [blank_start]Detachment[blank_end] of molecules [blank_start]from the solid surface[blank_end] to form solvated molecules at the solid liquid interface ([blank_start]liberation[blank_end])
2. [blank_start]Transport[blank_end] from this interface [blank_start]to the bulk solution[blank_end] ([blank_start]diffusion[blank_end])
Depending on whether step 1 or step 2 is rate limiting, the dissolution process is either [blank_start]reaction-rate controlled[blank_end] or [blank_start]transport-rate controlled[blank_end]; it may be a combination of both.- ADetachment
- Bfrom the solid surface
- Cliberation
- DTransport
- Eto the bulk solution
- Fdiffusion
- Greaction-rate controlled
- Htransport-rate controlled
3The Noyes-Whitney Equation states that:
- Awhen surface area is constant, the dissolution rate (dW/dt or dm/dt) of a drug is proportional to the difference between its solubility — Cs, and its bulk solution concentration — Cb
- Bindependent of surface area, the dissolution rate (dW/dt or dm/dt) of a drug is proportional to the difference between its solubility — Cs, and its bulk solution concentration — Cb
- Cwhen surface area is constant, the dissolution rate (dW/dt or dm/dt) of a drug is proportional to the difference between its solid remaining concentration — Ct, and its bulk solution concentration — Cb
4The Noyes-Whitney equation defines the rate of dissolution of a solid when the process is diffusion controlled and involves no chemical reaction.
- AVerdadero
- BFalso
5Nernst and Brunner suggested that diffusion occurs across a thin [blank_start]stagnant[blank_end] layer of [blank_start]saturated[blank_end] solution, called the [blank_start]diffusion layer[blank_end] (or hydrodynamic boundary layer) into the bulk solution. This layer experiences [blank_start]no convection[blank_end] and is analogous to a membrane.
The Nernst-Brunner equation states that the rate of diffusion (dW/dt) is equal to the [blank_start]diffusion constant[blank_end] (D) multiplied by the [blank_start]surface area[blank_end] (A) divided by the [blank_start]thickness[blank_end] of the diffusion layer (h), all multiplied by the [blank_start]difference[blank_end] in saturated concentration (Cs) and concentration of the bulk solution(Cbulk).
Therefore dW/dt = DA/h * (Cs - Cbulk)- Astagnant
- Bsaturated
- Cdiffusion layer
- Dno convection
- Ediffusion constant
- Fsurface area
- Gthickness
- Hdifference
6Assumptions made by the Nernst-Brunner equation:
1. Drug dissolves [blank_start]uniformly from all surfaces[blank_end]
2. Particles are [blank_start]spherical[blank_end]
3. Particles are uniform [blank_start]size[blank_end]
4. Thickness of the diffusion layer is [blank_start]constant[blank_end]
5. Both h and Cs are assumed to be [blank_start]independent of particle size[blank_end]- Auniformly from all surfaces
- Bspherical
- Csize
- Dconstant
- Eindependent of particle size
7Mathematical models of release:
1. Zero order release model
[blank_start]Constant amount of drug is released[blank_end] per unit time. Minimizes potential peak/trough [blank_start]fluctuations[blank_end] and [blank_start]side effects[blank_end], while [blank_start]maximizing[blank_end] the time the drug concentration remains within the therapeutic window.
2. First order release model
Drug release [blank_start]depends on concentration[blank_end]. Release obeys the Noyes-Whitney (Nernst-Brunner) equation.
3. Hixson-Crowell release model
Describes drug release by dissolution in which the [blank_start]dimensions[blank_end] of the dosage form [blank_start]diminish proportionally[blank_end] but the [blank_start]geometric shape[blank_end] remains constant.
4. Higuchi release model
If drug is dispersed in a [blank_start]homogeneous granular polymer matrix[blank_end] that is non-erodible. If the first 60% of release occurs in accordance with the Higuchi equation (i.e. % cumulative drug release is [blank_start]linearly[blank_end] proportional to the [blank_start]square root[blank_end] of time) then it suggests release occurs by diffusion of the drug from the surface of the device.
5. Korsmeyer-Peppas release model
Semi-empirical equation (the so-called power law) to describe drug release from [blank_start]polymeric[blank_end] devices. Linear if [blank_start]log % drug release[blank_end] plotted against [blank_start]log of time[blank_end].- AConstant amount of drug is released
- Bfluctuations
- Cside effects
- Dmaximizing
- Edepends on concentration
- Fdimensions
- Gdiminish proportionally
- Hgeometric shape
- Ihomogeneous granular polymer matrix
- Jlinearly
- Ksquare root
- Lpolymeric
- Mlog % drug release
- Nlog of time
8Empirical dissolution models have many inherent drawbacks, namely that the elucidation of the [blank_start]underlying mass transport mechanisms[blank_end] is not possible and [blank_start]not a single characteristic parameter[blank_end] of the dosage form is related to the intrinsic dissolution rate of the drug. Therefore, these studies do result in [blank_start]incomplete[blank_end] process and product understanding.
- Aunderlying mass transport mechanisms
- Bnot a single characteristic parameter
- Cincomplete
Información
- Descripción
- (Medicines) PHCY211 Test sobre MD4 How drugs dissolve, creado por Mer Scott el 12/05/2018.
- Autor
- Mer Scott
- Idioma
- English
- Visitas
- 7
- Etiquetas
- Valoración
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