Table of Contents
- 1 What determines volume of distribution?
- 2 What does volume of distribution mean in pharmacology?
- 3 What two factors can change the volume of distribution?
- 4 Which drug has highest volume of distribution?
- 5 Does volume of distribution change with age?
- 6 What are the determinants of volume of distribution?
- 7 How is volume of distribution measured in liters?
What determines volume of distribution?
Volume of distribution (Vd), represents the apparent volume into which the drug is distributed to provide the same concentration as it currently is in blood plasma. It is calculated by the amount of the drug in the body divided by the plasma concentration [19].
What does volume of distribution mean in pharmacology?
The volume of distribution (Vd) is a pharmacokinetic parameter representing an individual drug’s propensity to either remain in the plasma or redistribute to other tissue compartments.
Why is it called apparent volume of distribution?
A Volume of distribution This calculated value does not correspond to an anatomical or physiological part of the organism and can be much larger than the volume of total body water. It is therefore called ‘apparent’ volume of distribution.
What is considered high volume of distribution?
If the volume of distribution is larger than 42, the drug is thought to be distributed to all tissues in the body, especially the fatty tissue. Some drugs have volume of distribution values greater than 10,000 L! This means that most of the drug is in the tissue, and very little is in the plasma circulating.
What two factors can change the volume of distribution?
The major determinants of Vd are drug properties which affect protein binding and tissue binding. These consist of molecule size, charge, pKa, and the lipid/water partition coefficient.
Which drug has highest volume of distribution?
Examples
| Drug | VD | Comments |
|---|---|---|
| Warfarin | 8 L | Reflects a high degree of plasma protein binding. |
| Theophylline, Ethanol | 30 L | Represents distribution in total body water. |
| Chloroquine | 15000 L | Shows highly lipophilic molecules which sequester into total body fat. |
| NXY-059 | 8 L | Highly charged hydrophilic molecule. |
What is the use of apparent volume of distribution?
Volume of distribution (Vd) is the apparent volume into which a drug disperses in order to produce the observed plasma concentration. Vd is used to calculate loading doses, much as clearance is used to calculate maintenance dose.
Which type of drug has fairly high apparent volume of distribution?
Its apparent volume of distribution is close to total body water. Because it does not bind to plasma proteins this suggests it does not bind extensively to tissues either. Digoxin has a very large apparent volume of distribution – several times bigger than the typical human physical volume of 70 L.
Does volume of distribution change with age?
The volume of distribution is decreased in elderly patients. As a result, loading doses should be reduced by approximately 20%[60].
What are the determinants of volume of distribution?
The major determinants of Vd are drug properties which affect protein binding and tissue binding. These consist of molecule size, charge, pKa, and the lipid/water partition coefficient.
How is the volume of distribution of a drug determined?
Volume of distribution. For a drug that is highly tissue-bound, very little drug remains in the circulation; thus, plasma concentration is low and volume of distribution is high. Drugs that remain in the circulation tend to have a low volume of distribution.
How is the volume of distribution ( Vd ) calculated?
By definition, Vd is a proportionality constantthat relates the total amount of drug in the body to the plasma concentration of the drug at a given time. [1][2][3]The following equation can represent Vd: Volume of Distribution (L) = Amount of drug in the body (mg) / Plasma concentration of drug (mg/L) Based on the above equation:
How is volume of distribution measured in liters?
The unit for Volume of Distribution is typically reported in liters. As body composition changes with age, V D decreases. The V D may also be used to determine how readily a drug will displace into the body tissue compartments relative to the blood: .