Do water soluble drugs have low volume of distribution?
Drugs such as highly water-soluble compounds, which are confined intravascularly, have a small volume of distribution (approximately equal to intravascular volume), whereas lipophilic drugs that distribute to tissues have a large volume of distribution (that may be so large as to exceed total body water).
How does solubility affect drug distribution?
Solubility plays a critical role in drug effectiveness. Without it, a drug substance cannot be absorbed, leading to low bioavailability. Poor solubility of drugs also leads to other issues, such as challenges with metabolism or permeability, interactions with other drugs or the need to extend drug release.
What factors affect distribution of a drug?
Several factors impact drug distribution. These factors include the concentration of drug transporters in blood, pH, perfusion, body water composition, body fat composition, and most certainly disease conditions (e.g., volume depletion, burns, third spacing).
What are the distribution compartments of a drug?
The distribution of a drug between tissues is dependent on vascular permeability, regional blood flow, cardiac output and perfusion rate of the tissue and the ability of the drug to bind tissue and plasma proteins and its lipid solubility.
What factors affect 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. |
Why is water solubility an important factor in drug design?
Solubility is one of the important parameters to achieve desired concentration of drug in systemic circulation for achieving required pharmacological response [12]. Poorly water soluble drugs often require high doses in order to reach therapeutic plasma concentrations after oral administration.
How are drugs distributed?
Each drug is uniquely distributed in the body. Some drugs distribute mostly into fat, others remain in extracellular fluid, and others are bound extensively to specific tissues. Many acidic drugs (eg, warfarin, aspirin) are highly protein-bound and thus have a small apparent volume of distribution.
What are water soluble drugs?
Drugs that dissolve in water (water-soluble drugs), such as the antihypertensive drug atenolol, tend to stay within the blood and the fluid that surrounds cells (interstitial space). Drugs that dissolve in fat (fat-soluble drugs), such as the antianxiety drug clorazepate, tend to concentrate in fatty tissues.
How do water-soluble drugs work?
What are 3 factors that affect solubility?
Temperature, pressure and the type of bond and forces between the particles are few among them.
- Temperature: By changing the temperature we can increase the soluble property of a solute.
- Forces and Bonds: Like dissolves in like.
- Pressure: Gaseous substances are much influenced than solids and liquids by pressure.
What is water soluble drugs?
Where does drug distribution occur?
Why do drugs need to be water soluble?
How does water solubility affect drug absorption?
When delivering an active ingredient orally, it must first dissolve in gastrointestinal fluids before it can then permeate the membranes of the gastrointestinal tract to reach systemic circulation. Therefore, a drug with poor aqueous solubility will exhibit dissolution rate-limited absorption.
What does distribution mean in pharmacokinetics?
Distribution is the process by which drug passes from the bloodstream to body tissues and organs. It is how a drug moves from intravascular space, e.g. blood vessels, to extravascular space, e.g. body tissues, as it is carried around the body by the circulatory system (figure 1).
How is medicine distributed in the body?
In the bloodstream, drugs are transported partly in solution as free (unbound) drug and partly reversibly bound to blood components (eg, plasma proteins, blood cells). Of the many plasma proteins that can interact with drugs, the most important are albumin, alpha-1 acid glycoprotein, and lipoproteins.