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The rate of drug absorption will be affected by:
1. Rate of release of drug from pharmaceutical preparation
2. Membrane permeability of drug
3. Surface area in contact with drug
4. Blood flow to site of absorption
5. Destruction of drug at or near site of absorption
Additives that have variable effects on rates of dissolution
Increases membrane permeability
a) Presence of aliphatic and aromatic structures
b) Absence of polar groups
Decreases membrane permeability
a) Weak ACIDS in INTESTINES are mostly ionized
b) Weak BASES in STOMACH are mostly ionized
Great for patient that is vomiting or cannot swallow medicine; 50% bypasses liver
1. Where drugs act
2. Where drugs are eliminated
3. How long drugs last in the body
Drug transported by the liver into the intestines where it is reabsorbed; increases the time it lasts in the body
Determinants of drug distribution
1. Organ blood flow
2. Barriers to drug diffusion
3. Adipose tissue
4. Tissue protein binding
5. Plasma protein binding
6. Drug transport
7. Ion trapping
Capillaries with tight junctions
Drug molecules must diffuse across (transcellular); must be lipophilic
Effects of adipose tissue
The distribution of lipophilic drugs will be different in thin vs. obese patients
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