#4 Flashcards
Why are so many drugs in pill form?
Because the enter you system slower, and make it harder to OD.
The _____ the PC (partition coefficient) the more likely the drug will be absorbed by passive diffusion.
Larger the PC
______ molecules are more likely to be absorbed by passive diffusion.
smaller molecules
*Lipophilic molecules also use this method.
What is PC (partition coefficient)?
How well a chemical can enter cell membrane (olive oil) *Higher = more likely to cross membrane.
Do charged molecules enter the cell membrane well?
No!
How does pH effect passive diffusion of drugs?
Acidic drugs are absorbed more in the stomach. (acidic pH in stomach)
Basic drugs are absorbed more in the small intestines. (intestine pH is 3-7)
_________Transporters can kick drugs out of cells.
ABC transporters (use ATP) *active transport
_______ Transporters are important for transport of certain drugs that are organic acids or bases.
SLC Transporters (Exchange Na+ or K+)
What factors affect oral absorption of drugs?
- pH
- surface area
- Gastric emptying time (time in stomach)
- dosage form
- Drug inactivation
What are the other routes to administer drugs other than oral?
- inhalation
- intravenous
- Intramuscular
- Subcutaneous
- Topical
Describe distribution of drug through tissues….
A. Capillary penetration to the interstitial fluid.
B. Entry into cells from interstitial fluid.
C. Restricted distribution into CNS-blood brain barrier.
*No gaps in endothelium, sheaths surrounds, drugs efficiently transported out of epithelium back into blood stream.
Which drugs are faster? Water soluble or Lipophilic?
Lipophilic are faster
*Water soluble drugs go through endothelial gaps are slower.
What is Volume of Distribution?
Indication of how much a drug is distributed, based on how much is in the plasma and how much was added.
*Q/C =Vd
Q = amount of drug administered
C= concentration of drug in plasma at Eq.
Average person volume = ?
3 liters of plasma
9 liters of interstitial space
29 liters cells
TOTAL = 41 liters
- IF a drug never leaves blood/plasma Vd = 3 liters
- IF drug distributed equally everywhere Vd = 41 liters.
Describe the 2 phases of drug metabolism..
Phase 1 = add (uncover) functional group
Phase 2 = Conjugation
______ is the most important place for drug metabolism.
The liver
What role does the Smooth E.R of hepatocytes? What types of chemical rxns are taking place here?
It has membrane bound enzymes that metabolize drugs.
Chemical rxns going on here:
1. Oxidations (P450 enzymes, Flavin monooxygenases)
2. Reductions (Some hepatocyte, mainly enteric bacteria)
3. Hydrolysis (ester and amides)
4. Dehalogenation
5. Glucuronide conjugation
_________ are designed to remove foreign substances.
Microsomal enzymes
_______ is when drug mimics natural substance.
Non-microsomal metabolism
- oxidation
- reductions
- hydrolysis
- conjugation
What are the 6 factors that affect drug metabolism?
- Entry into lever (usually slow into the liver and fast once in)
- Enzyme inhibition
- Enzyme induction
- Genetics
- Age
- Pathology
What are the 3 components of drug excretion?
- glomerular filtration
- tubular reabsorption
- active transport
What is the major filter of glomerular filtration?
The basement membrane
Drugs that are filtered but not reabsorbed or secreted back clear at ______.
130 mL/min
*If Vd is 12 L the drug will have a t1/2 of about 1 hr in the plasma.
Drugs that are actively secreted and not reabsorbed may clear as fast as _______.
650 mL/min
*If Vd id 12 L the drug will have a t1/2 of about 13 min in the plasma
