Drug Transport and Absorption Flashcards
(30 cards)
What does the ionization of a weak electrolyte depend on?
pKa of the drug
pH of the solvent
Do drug concentrations stay the same on either side of a membrane that has differing pH’s?
No, they are unequal it has a higher drug concentration on the side with a pH closer to its own. (side of greater ionization)
How ionized do weak acidic drugs become in the stomach and plasma?
Largely non-ionized in stomach
40-50% non-ionized in plasma
How ionized do weak basic drugs become in the stomach and plasma?
Mainly ionized in stomach
Non-ionized in plasma
How do you trap weak acidic drugs in urine?
Administering sodium bicarbonate to force alkaline diuresis
How do you trap weak basic drugs in urine?
Administering ammonium chloride to cause acidification of urine
What sort of drugs are collected in breast milk?
Weak bases
Why do weak acids remain less concentrated in breast milk?
Plasma is more alkaline than breast milk and thus draws it out
How does lower pKa affect acidic drugs?
Creates a greater degree of ionization
How does higher pKa affect basic drugs?
Creates a greater degree of ionization
What happens if pH = pKa?
Drug is 50% ionized
What does AMDE stand for?
Absorption
Distribution
Metabolism
Excretion
What is absorption?
Movement of drug from the site of administration to systemic circulation
What are the routes of administration that have no first pass effect?
Parenteral and Topical/transdermal/inhaled
What is intravenous administration advantageous for?
Narrow therapeutic index
Poor absorption
Rapid metabolism
Poor blood circulation
What are the disadvantages of intravenous drug administration?
Drug overdose
Introduce bacteria
Disrupt hemodynamics
What should you not introduce intravenously?
Insoluble drugs or oils
What is subcutaneous administration used for?
Non-irritating drugs
What are the advantages of intramuscular administration?
Rate of absorption is good
More irritating drugs
Larger volumes
How does using insoluble or oily drugs affect the absorption of intramuscular administration?
Slower absoprtion
How does absorption in the mouth compare to that of the gastrointestinal tract?
4X faster from mouth
What kind of drugs are the ideal candidates for sublingual administration?
Non-ionized
Highly lipid soluble
Rapid dissolution
What are the advantages of the oral route of administration?
Common
Safest
Convenient
Economical
What are the advantages of rectal administration?
Administer labile drugs
Compliance with unconscious patients or patients with swallowing issues
Partial avoidance of the first pass effect
