What is the significance of volume of distribution?
ABSTRACT: Volume of distribution is one of the most important pharmacokinetic properties of a drug candidate. It is a major determinant of half-life and dosing frequency of a drug. For a similar log P, a basic molecule will tend to exhibit higher volume of distribution than a neutral molecule.
What is the importance in knowing the volume of distribution of a drug?
Drugs that remain in the circulation tend to have a low volume of distribution. Volume of distribution provides a reference for the plasma concentration expected for a given dose but provides little information about the specific pattern of distribution. Each drug is uniquely distributed in the body.
What does a high Vd mean?
Definition/Introduction A drug with a high Vd has a propensity to leave the plasma and enter the extravascular compartments of the body, meaning that a higher dose of a drug is required to achieve a given plasma concentration. (High Vd -> More distribution to other tissue)
What does a large volume of distribution mean?
The larger the volume of distribution, the more likely that the drug is found in the tissues of the body. The smaller the volume of distribution, the more likely that the drug is confined to the circulatory system.
How does volume of distribution affect clearance?
Volume of distribution per se has no effect on clearance or on average steady-state blood levels. Although changes in tissue binding will affect partition coefficient and apparent volume of distribution, such changes will have no effect on average steady-state blood levels of either total or free drug.
What will be the apparent volume of distribution of warfarin?
Warfarin is extensively bound to plasma proteins. About 99% of warfarin in plasma is bound to albumin leaving only 1% unbound. Based on total warfarin concentration the apparent volume of distribution is 10 L.
How does volume of distribution affect half life?
Elimination half-life is increased by an increase in volume of distribution or a decrease in clearance, and vice versa. This is because a decrease in the efficiency of elimination (and therefore in clearance) would, of course, cause an increase in the time needed to reduce the plasma concentration by 50 percent.
What is the apparent volume of distribution of digoxin?
Digoxin is widely distributed throughout body tissues and has a high apparent volume of distribution (about 6L/kg). Although most of the digoxin in the body is in skeletal muscle it is found in highest concentrations in the heart, kidneys and brain.
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.
How does volume of distribution affect bioavailability?
Increases in the volume of distribution for a medication will not alter the average steady state concentration, but will result in lower peak and higher trough concentrations. Apparent volume of distribution is dependent on the drug’s lipid or water solubility, plasma protein binding as well as tissue binding.
What is the apparent volume of distribution?
Sample values and equations
| Characteristic | Description | Worked example value |
|---|---|---|
| Volume of distribution | The apparent volume in which a drug is distributed (i.e., the parameter relating drug concentration in plasma to drug amount in the body). | 6.0 L |
| Concentration | Amount of drug in a given volume of plasma. | 83.3 mmol/L |
How does volume of distribution affect drug?
The volume of distribution (Vd) specifies how widely the drug is distributed in the body. It represents the apparent volume into which the drug is dissolved. The larger is the Vd, the less it is able to reach the tissues it is expected to reach and exert its pharmacological effect.
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. 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:
Is the volume of distribution a real thing?
The volume of distribution is a hypothetical amount, meaning that it is not a real volume, but instead is a concept of volume. This lesson will discuss the definition and significance of volume of distribution related to drug concentrations.
How is the volume of distribution of a drug calculated?
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].
How is the volume of distribution related to plasma concentration?
The volume of distribution is a proportionality constant, relating the total amount of drug present in the organism to its plasma concentration at the same moment. It is the volume in which the drug apparently distributes in a concentration equal to its concentration in plasma.