Factors that affect the volume of distribution include plasma protein binding, obesity, edema, and tissue binding. In obesity, lipophilic drugs are distributed into adipose tissue and tend to accumulate.
What are the factors that affect drug distribution?
Drug distribution is impacted by several factors related to the drug and the body. The drug-related factors include blood and tissue binding proteins, pH, and perfusion. The body-related factors include body water composition, fat composition, diseases (e.g., volume depletion, burns, third spacing).
What is volume of distribution?
This chapter aims to offer a sensible and memorable definition, and then discuss some of the patient factors and drug factors which influence a volume of distribution (or the measurements used to determine it). Volume of distribution (Vd) is the apparent volume into which a drug disperses in order to produce the observed plasma concentration.
What are the factors that affect ventricular volume of distribution?
Patient factors which affect Vd include age, gender, body muscle/fat proportion, level of hydration, water distribution (oedema, effusions, ascites, pregnancy) and extracorporeal sites of distribution (circuit, filters, oxygenator etc) Published literature which discusses volume of distribution is hardly rare.
How does volume of distribution affect steady state concentration?
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 increases distribution volume?
Volume of distribution may be increased by kidney failure (due to fluid retention) and liver failure (due to altered body fluid and plasma protein binding). Conversely it may be decreased in dehydration.
What two factors can change the volume of distribution Vd?
Factors that affect the volume of distribution include plasma protein binding, obesity, edema, and tissue binding.
What factors impact distribution?
Drug distribution is affected by many factors, including plasma or tissue protein binding, body weight, body composition, and body fluid spaces (8).
What affects the distribution 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. pH partition plays a major role as well.
Does VD change with weight?
Vd varies with individual height and weight. The most important causes of variation of Vd are accumulation of fat (for lipid-soluble drugs) such as for obese patients, or accumulation of fluids (for water-soluble drugs) such as ascites, edema or pleural effusion.
How does protein binding affect volume of distribution?
Decreased plasma protein binding leads to an increase in free plasma fraction causing an increase in volume of distribution and a shorter elimination half life. The increase in the apparent volume of distribution and the shorter elimination half life cause a decrease in total plasma concentration.
What are the factors to consider in determining the distribution strategy?
When planning your distribution strategy, there are several factors to consider, including:Product type. Depending on the type of product or service you offer, your distribution strategy may vary. ... Customer base. ... Warehouse and transportation logistics. ... Wholesale. ... Retail. ... Franchisor. ... Distributor. ... A toothpaste company.More items...
Which characteristics is most likely to be associated with a high apparent volume of distribution?
Which of the following characteristics is most likely to be associated with a high apparent volume of distribution? The answer is E. A high apparent volume of distribution is associated with an extensive binding to tissue constituents.
What are the determinants of distribution channels?
The issue is analyzed by an overview of determinants of distribution structure in literature. The results show that the four most important factors that affect company's choice of distribution channel are: (1) consumer habits; (2) product characteristics; (3) the market; and (4) company factors.
What are three factors that affect drug distribution throughout the body quizlet?
Three major factors determine drug distribution: blood flow to tissues, the ability of a drug to exit the vascular system, and the ability of a drug to enter cells.
What is the volume of distribution of a drug?
Simply defined, the volume of distribution is the volume of plasma that would be necessary to account for the total amount of drug in the patient's body, if that drug were present throughout the body at the same concentration as found in the plasma.
Which type of drug have high 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).
What are the two factors which decides the distribution of population?
The main factors determining population distribution are : climate, landforms, topography, soil, energy and mineral resources, accessibility like distance from sea coast, natural harbours, navigable rivers or canals, cultural factors, political boundaries, controls on migration and trade, government policies, types of ...
What are the factors that determine volume of production?
There are various factors which affect the volume of production which includes:Availability of natural resources.Availability of raw materials.Technology.Availability of capital.Transport facilities.Political conditions.Climate.Efficiency of labour.
What are the factors the volume of production?
Economists traditionally divide the factors of production into four categories: land, labor, capital, and entrepreneurship.
What factors affects the volume of production in an economy?
Key Takeaways. Factors of production is an economic term that describes the inputs used in the production of goods or services to make an economic profit. These include any resource needed for the creation of a good or service. The factors of production are land, labor, capital, and entrepreneurship.
What is volume of distribution?
Volume of distribution is a pharmacokinetic concept which is used to describe the distribution of drugs in the body as relative to the measured concentration. In brief, it is the apparent volume into which the drug appears to be distributed when only the sample concentration is considered. It is a purely theoretical volume, which can substantially exceed the total body volume, or potentially even be infinite in size. Among many other uses, the volume of distribution (V D or Vd) plugs into loading dose calculations. It can also help you decide instantly whether your drug is going to be easily cleared by dialysis, and it can be used to retrospectively estimate the magnitude of a drug overdose.
What are the determinants of VD?
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 does timing affect drug concentration?
It is clear that timing plays a major role in this, because the measured drug concentration will vary depending on the rate and extent of absorption. Even with IV administration there is going to be some delay. A discussion of the volume of distribution as dose divided by concentration meets with a limitation of the multi compartment model, which is the assumption that the drug is distributed equally and instantly throughout the compartment. In reality, drug concentration in the sample will vary over time because it takes time for the drug to distribute around the body, and a concentration taken within minutes of administration will be very different to the concentration taken many hours later. Clearly these will produce completely different Vd values. So, which concentration value should we use to calculate the "gospel" Vd?
What happens if you ignore the distribution of a drug into the tissues?
Obviously if you completely ignore the distribution of the drug into the tissues your volume of distribution estimate is going to be inaccurate for the purpose of determining such things as loading doses. The alternative approach is to ignore everything but the tissue distribution. This method takes the slow late stages along the concentration/time curve (the terminal elimination phase) and extrapolates a line of best fit from them.
What is the volume of initial dispersion of a drug?
So, by this method, you measure the volume of initial dispersion of the drug. This volume is usually called either V initial, or V c, and it represents the behaviour of the drug during the first rapid phase of distribution through the central compartment. It is generally determined by the degree of protein binding. Drugs which are highly protein-bound will have a larger V initial if you intend to measure free drug levels.
Why are VDS lower in women?
Female Vds tend to be lower than male Vds due to the generally lower body water content ( Soldin & Mattison, 2009) Pregnancy. Both the body water and the body fat content increases, and therefore the Vd increases for most drugs. Not to speak of the possible distribution into amniotic fluid and foetus.
Why is V Ss lower than V area?
It is always going to be slightly lower than V area because of the effect of clearance on the β terminal elimination time constant.
How to calculate volume of distribution?
It is calculated by dividing the dose that ultimately gets into the systemic circulation by the plasma concentration at time zero (Cp0 ):
Why is volume of distribution normalized to body weight?
For convenience, the volume of distribution is usually normalized to body weight because it is reasonable to expect that the volume of distribution will increase with body weight. In the above example, this volume of distribution in a horse weighing 500 kg could be expressed as 2 L/kg of body weight.
How is VD calculated?
It is calculated by the amount of the drug in the body divided by the plasma concentration [19]. Thus, Vd reflects the extent to which the drug is present in extravascular tissues but not in plasma. Lipid solubility can affect Vd, as highly lipid-soluble drugs have good cell penetration, resulting in high Vd.
What are the consequences of growth and maturational changes in body composition?
A major consequence of growth and maturational changes in body composition may be differences in volume of distribution. In general, neonates and infants have larger distribution volumes for water-soluble drugs and smaller volumes for lipophilic drugs.
What is the largest factor in drug dosing during the initial stages of septic shock?
VD is the largest factor in drug dosing during the initial stages of septic shock, and therefore loading doses are necessary to obtain therapeutic levels quickly (e.g., vancomycin 25–30 mg/kg). So, larger doses of drugs with a large VD are necessary until septic shock resolves or fluid is removed.
Why is VD important?
In addition, Vd is helpful in predicting the initial maximum concentration for an IV bolus and can be used to predict the effectiveness of dialysis in treating drug intoxication during an emergency [18].
Does volume of distribution affect steady state concentration?
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 are the factors that affect distribution?
Factors Pertaining to the Product 2. Factors Pertaining to the Consumer or Market 3. Factors Pertaining to the Middlemen 4. Factors Pertaining to the Producer or Company B. Factors to Consider When Choosing a Distribution Channel 1. Environmental Factors 2. Financial Factors 3. External Factors C. Criteria for Selection of Distribution Channel 1. Nature of the Market 2. Nature of the Product 3. Degree of Competition 4. Size of the Organisation 5. Degree of Control 6. Financial Strength 7. Cost of Marketing 8. Environmental Factors.
What are the factors that determine the distribution channel?
Environmental Factors 2. Financial Factors 3. External Factors C. Criteria for Selection of Distribution Channel 1. Nature of the Market 2. Nature of the Product 3. Degree of Competition 4. Size of the Organisation 5. Degree of Control 6. Financial Strength 7.
Why are intermediaries important?
But because intermediaries carry a wide range of competitive products, it is often not possible to achieve any special treatment for such products. In such cases, the indirect channel may be used and exclusive franchise may be offered by appointing wholesalers as distributors and retailers as dealers (where intensive distribution is desired). This may ensure channel loyalty and aggressive selling by intermediaries.
How does marketing products depend on middlemen?
The success of marketing products depends on the attitudes of the middlemen. When middlemen believe in the policies of the company and are interested to carry on the mission of the company, they work as extensions of the company but then when such attitudes are absent and they rather pose hurdles for the company, firms need to have their own method of distribution.
How can a company build its own distribution network?
A company may build its own distribution network if its activities are on a national scale, if it has a large product mix, and if its financial position is strong and sound. If the financial strength of the company is satisfactory, it can finance its own distribution network for the marketing of its products. It can build its own marketing organisation. But if the firm is small and its financial structure is weak, it will have to depend upon middlemen for the distribution of its products.
When the number of customers (both existing and potential) are small, the distribution channel covers a small area?
When the number of customers (both existing and potential) are small the distribution channel covers a small area while in case of products that have large number of products, the channels is widely scattered having many wholesalers and retailers
Why is direct channel uneconomical?
When the unit value of a product is high, it is usually economical to choose direct channel (choices A and B) because the high cost of direct distribution constituted only a small percentage of the selling price of the product. But when the unit value is low and the amount involved in each transaction is generally small, direct channel becomes uneconomical unless the product order / indent is composed of an assortment of a large number of low unit value products making the whole transaction substantial.
What are the factors that affect drug distribution?
The drug-related factors include blood and tissue binding proteins, pH, and perfusion. The body-related factors include body water composition, fat composition, diseases (e.g., volume depletion, burns, third spacing).
How does body composition affect drug distribution?
Body composition and metabolic factors also affect drug distribution. For example, during the last trimester of pregnancy, plasma volume expands, so there is an overall diluting effect on plasma proteins. There is also a change in adipose tissue.
How does high reserves of plasma protein bound drugs cause prolonged effects?
High reserves of plasma protein-bound drugs can cause prolonged effects by creating a sustained release mechanism. [3] . Drug distribution is the disbursement of an unmetabolized drug as it moves through the body’s blood and tissues.
Does competition affect plasma binding?
Competition for plasma binding can influence drug effects. For example, Aspirin and Warfarin are known to compete for the same plasma protein binding site. Administering both drugs at the same time will increase the unbound drug, thereby potentiating their effects and potentially lead to bleeding risk.[8] .
What influences the distribution of drugs?
Drugs can bind to many of the blood components, which influences the distribution of the drugs.
Which properties of drugs influence distribution?
Physicochemical properties of the drug that influence distribution are: Molecular size, degree of ionization, partition coefficient, and stereochemical nature.
What increases the volume of drugs during pregnancy?
The volume for distribution of drugs increases during the pregnancy for the growth of the uterus, placenta, and fetus.
How does stereochemical nature affect drug distribution?
The stereochemical nature of the drug will influence the distribution of the drug when it tends to interact with macromolecules like the proteins.
What is distribution in medicine?
1. Distribution - This involves the reversible transfer of a drug between compartments.
Where does a drug flow?
The drug can flow freely into the extracellular space between the capillary endothelium wall and the choroid cells.
