Quiz
L9 Absorption
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1Drug absorption is the ability of a drug to pass through a biological [blank_start]membrane[blank_end]. Absorption is defined with the [blank_start]absorption rate[blank_end] constant, Ka, and the Tmax, time at which concentration of the drug is [blank_start]maximum[blank_end]. The determinants of drug absorption from the gut are:
1. [blank_start]Disintegration[blank_end] of the dosage form and [blank_start]dissolution[blank_end] of the drug
2. Physiology of [blank_start]gastrointestinal tract[blank_end]
3. Food or drug [blank_start]interactions[blank_end] in the gut lumen
4. Passage through the gut [blank_start]wall[blank_end]- Amembrane
- Babsorption rate
- Cmaximum
- DDisintegration
- Edissolution
- Fgastrointestinal tract
- Ginteractions
- Hwall
2Disintegration of the dosage form depends on the release characteristics of [blank_start]dosage form[blank_end], and the physicochemical [blank_start]properties[blank_end] of the drug(charge, particle [blank_start]size[blank_end], etc).
Concerning the gut physiology, absorption rate is affected by gastric [blank_start]emptying[blank_end]. This is highly [blank_start]variable[blank_end] between people. When fasting, it typically takes an [blank_start]hour[blank_end] for solid forms and [blank_start]10-20 minutes[blank_end] for drugs in solution. After eating it is much [blank_start]slower[blank_end] (> 7 h in some cases). Gastric emptying time may impact absorption rate for drugs that readily dissolve in the stomach (paracetamol) or enteric coated drugs
Insoluble drugs may have [blank_start]enhanced[blank_end] absorption if transit time is slow- Adosage form
- Bproperties
- Csize
- Demptying
- Evariable
- Fhour
- G10-20 minutes
- Hslower
- Ienhanced
3Altered motility of the gut will usually impact the extent, not rate of absorption.
- ATrue
- BFalse
4Food or drug interactions in the gut lumen may affect absorption rate.
They can do this by [blank_start]altering[blank_end] pH, and therefore [blank_start]solubility[blank_end]. E.g. acid suppressants ([blank_start]PPIs[blank_end]) & dabigatran in the wrong pH can decrease absorption by about 30%. [blank_start]Complexation[blank_end] can also alter absorption. E.g. Di- and tri- valent ions in [blank_start]antacids[blank_end] can affect alendronate and quinolone antibiotics.- Aaltering
- Bsolubility
- CPPIs
- DComplexation
- Eantacids
5Passive diffusion is the primary absorption process for most drugs.
- ATrue
- BFalse
6Rate of flux (diffusion) will depend on:
- Athe concentration gradient and the drug permeability
- Bthe concentration gradient and drug ionisation state
- Cthe drug permeability and drug ionisation state
- Dthe membrane permeability and the concentration gradient
7Drug permeability is determined by:
(Select all that apply)- AMolecular size
- BIonisation state
- CLipophilicity
- DConcentration gradient
- EDosage form
8Small polar drugs, e.g. alcohol can be absorbed by [blank_start]paracellular[blank_end] diffusion.
Many endogenous compounds (e.g. glucose) are absorbed by [blank_start]facilitated[blank_end] transport. No input of energy is required as movement is [blank_start]down[blank_end] a concentration gradient. The transporters involved are highly [blank_start]selective[blank_end].
Active transport is where energy is required. Transporters are [blank_start]saturable[blank_end] and can be competitively inhibited (consider drug [blank_start]interactions[blank_end]). These include [blank_start]efflux[blank_end] transporters (e.g. P-glycoprotein) that [blank_start]limit[blank_end] drug absorption from the gut.- Aparacellular
- Bfacilitated
- Cdown
- Dselective
- Esaturable
- Finteractions
- Gefflux
- Hlimit
9An absorption rate constant of 0.5 which has units of h-1 suggests that approximately 50% of the remaining drug in the gut will be absorbed every hour, but this is a gross approximation.
- ATrue
- BFalse
10Oral absorption often approximates first order PK behaviour.
- ATrue
- BFalse
11If the drug is absorbed across the gut at a [blank_start]constant[blank_end] rate, then it will follow [blank_start]zero[blank_end] order absorption. The rate of absorption will be independent of the [blank_start]amount[blank_end] of drug remaining in the gut lumen. This may occur because of [blank_start]saturable[blank_end] transporter processes, or due to [blank_start]slow[blank_end] release from the dosage form (e.g. sustained release tablet).
- Aconstant
- Bzero
- Camount
- Dsaturable
- Eslow
12Absorption dependant PK pccurs when the half-life of absorption is longer than the elimination half-life.
- ATrue
- BFalse
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- Description
- PHCY310 Quiz on L9 Absorption, created by Mer Scott on 07/04/2019.
- Author
- Mer Scott
- Language
- English
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