drugs crossing the cell membranes phospholipid cell layer - ANS--drugs must be LIPID
j j j j j j j j j j j j
SOLUBLE in order to pass through the membrane
j j j j j j j j
- WATER SOLUBLE drugs penetrate the cell membrane through channels and pores
j j j j j j j j j j j
Absorption j
1. direct penetration of the membranes
j j j j j
2. channels and pores
j j j
3. transport systems - ANS-the movement of a drug from its site of administration to the
j j j j j j j j j j j j j j j
blood
j
How do drugs cross membranes?
j j j j
1. Direct penetration of the membranes - ANS-- use by MOST drugs
j j j j j j j j j j j
- most drugs to large to pass thru channels and pores
j j j j j j j j j j
- most drugs lack transport systems
j j j j j
- drugs must be lipid soluble to be able to penetrate cellular membranes = lipophilic drugs
j j j j j j j j j j j j j j j
2. channels and pores - ANS-only very small ions such as potassium and sodium can pass
j j j j j j j j j j j j j j j
through cell membranes
j j j
3. transport systems - ANS-- are carriers that can move drugs from one side of the
j j j j j j j j j j j j j j j
membrane to the other
j j j j j
- are selective
j j
Movement of drugs across membranes - ANS--drugs must cross membranes (pass
j j j j j j j j j j
through cells) to enter the blood from their site of administration
j j j j j j j j j j j j
- drugs must then leave the blood (vascular systems) to get to their SITE OF ACTION
j j j j j j j j j j j j j j j
- drugs must then cross membranes again to be metabolized and excreted
j j j j j j j j j j j
pharmacokinetic phase: Absorption - ANS-process that occurs between the time a drug j j j j j j j j j j j
enters the body and the time it enters the bloodstream to be circulated
j j j j j j j j j j j j j j
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