Effects of Hydrophilic and Lipophilic Tendencies on the Biological Properties of Drugs
The characteristics conferred by predominant hydrophilic or lipophilic properties. Most drugs need both properties: lipophilic to cross membranes; hydrophilic to enable transport in and distribution by body fluids.
Predominantly lipophilic
- Good membrane penetration
- Good absorption after oral administration
- Distributed in body fat
- Cross blood–brain barrier
- Hepatic metabolism
- Longer half-life
- First-pass effect possible
- Clearance dependent on liver function and release from fat storage sites
- Biliary excretion of hydrophilic metabolites (molecular weight 400 Dalton)
- Possible interaction with other hepatically metabolized drugs
Predominantly hydrophilic
- Poor membrane penetration
- Poor absorption after oral administration
- Distributed in body water
- Does not cross blood–brain barrier
- Cleared renally unchanged
- Shorter half-life
- Clearance dependent on renal function
- Increased plasma protein binding
- Possible interaction with other protein-bound drugs
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