MODULE 6 PART 1: DRUG ABSORPTION Flashcards
(21 cards)
It is the rate-limiting step that determines release of drug from the dosage form.
Dissolution
How can dissolution be enhanced?
- By administering the drug in the salt form (e.g. phenytoin sodium, propanolol HCl)
- By decreasing the particle size of the drug - micronization.
Following dissolution, drug must be stable in its environment and must be sufficiently _____-soluble to diffuse to cell membrane, penetrate barrier, and enter the blood circulation.
lipid
Regardless of route of administration, drug must transverse a number of membrane before it reaches site of action. True or False?
True
How can drug molecules be transported?
- Passive diffusion of lipid soluble molecules (lipid diffusion)
- Passive diffusion of water-soluble molecules
- Carrier mediated transport by carrier protein
—- active transport
—- facilitated diffusion - Pinocytosis (endocytosis/exocytosis)
- Passive filtration (as in renal glomeruli)
- Passive via gap junctions
Absorption occurs throughout the GIT. What site specifically?
Small intestine because of its extensive area of rich blood supply
Drug absorption is great in colon. True or False?
False
Give some lipid-soluble drugs that are non-ionized and can be absorbed in gastric epithelium.
- NSAID
- Barbiturates
- Sulfonamides
- Nalidixic acid
- Nitrofurantoin
- Weak acid
Ionized form of drug is greatly absorbed in the stomach. True or False?
False, weak basis (ionized) are poorly absorbed.
E.g.: Ipioid analgesic, Quinidine, Ephedrine, Alkaloids
Rate of gastric emptying also affects the absorption. True or False?
True
For the drug to be absorbed on the skin, drug must penetrate the ____ layer.
keratin
Intact skin allows passage of small _____ substances, but retards diffusion of _____ soluble molecule.
lipophilic, H2O
What type of dosage form is greatly absorbed in skin?
Oil-in-water emulsion (e.g. aqueous cream)
Inhalants are absorbed through diffusion across the ?
Pulmonary alveolar epithelium
Solutes or drugs must first transverse the ____ wall to be absorbed.
capillary
If drug is in oily vehicle or suspensions, what route of administration should be prevented?
I.V.
Absorption of drug from IM or SC is rapid, if it is given in ____ solution.
aqueous
In I.M. or S.C., rate of absorption is determined by the ?
Vascularity of the area
It is the term for relative solubility of compound in lipid and water.
Partition coefficient
This refers to when a rate of process is dependent upon permeability coefficient and concentration gradient.
First order kinetic
This refers to acid and alkaline ion-trapping.
pH partitioning phenomenon
