2 - Distribution Flashcards
What % of body weight does total body water constitute?
60%
What % of body weight does intracellular fluid constitute?
40%
What % of body weight does extracellular fluid constitute?
20%
What % of body weight does plasma fluid constitute?
4%
What % of body weight does blood volume constitute?
7%
What is included in blood volume but NOT in plasma?
Red blood cells, which make up about 3% of body weight
Why is it important to know if a drug enters RBCs or not?
- If it enters RBCs, drug [ ] in plasma will be the same as drug [ ] in blood
- If it doesn’t enter RBCs, drug [ ] in plasma > drug [ ] in blood
What happens if a drug has a very large volume of distribution, ex: 2000 L?
It will go into tissues and less will be in plasma
Following absorption, the pattern of drug distribution is governed by ______
Rate of blood flow (perfusion) to each tissue and affinity of drug to accumulate in the tissue
What is important to note about tissues that are highly perfused?
Will rapidly equilibrate w/ the drug
What does low blood flow to a tissue mean?
Low amount of drug entering the tissue
Blood flow is an important factor in determining the ________ of drugs
Initial distribution
Which tissues are highly perfused?
- Adrenals
- Kidneys
- Thyroid
- Liver
- Portal-drained viscera
- Heart
- Brain
Which tissues are poorly perfused?
- Skin
- Muscle
- Connective tissue
- Fat
Drug accumulation into tissues is dependent upon ______
Blood flow and tissue affinity for the drug
What will happen to the tissue [ ] of drugs w/ low tissue affinity?
- Will equilibrate rapidly w/ plasma drug [ ]
- Will decline rapidly as the drug is eliminated from plasma
What happens to drugs w/ high tissue affinity?
Tend to accumulate or concentrate in the tissue, so will remain in tissues long after it is depleted in plasma or whole blood
Highly lipophilic drugs are extracted by ____ organs, so drug accumulation is _____
- Poorly perfused (ex: fat)
- Slow
Removal from fat tissue is _____
Extremely slow
Can chemicals remain in fat tissue for years?
Yes
What is the formula for volume of distribution?
Amount of drug added (mg) / drug concentration (mg/L)
What does albumin do?
Binds lipophilic compounds and acidic drugs
What does AAG do?
Binds basic drugs
Where are albumin and AAG found?
In blood
