What is drug distribution in pharmacology? Drug distribution is the disbursement of an unmetabolized drug as it moves through the body’s blood and tissues. The efficacy or toxicity of a drug depends on the distribution in specific tissues and in part explains the lack of correlation between plasma levels and the effects that are seen.
What is distribution process in pharmacology? Distribution in pharmacology is a branch of pharmacokinetics which describes the reversible transfer of a drug from one location to another within the body. Once a drug enters into systemic circulation by absorption or direct administration, it must be distributed into interstitial and intracellular fluids.
What determines drug distribution? Drug distribution is affected by many factors, including plasma or tissue protein binding, body weight, body composition, and body fluid spaces (8). Of these, total body weight, muscle mass, and fat composition are the major determinants of drug distribution, and women may differ from men in both of these factors.
How are most drugs distributed? After a drug is absorbed into the bloodstream (see Drug Absorption), it rapidly circulates through the body. The average circulation time of blood is 1 minute. As the blood recirculates, the drug moves from the bloodstream into the body’s tissues. Once absorbed, most drugs do not spread evenly throughout the body.
What is drug distribution in pharmacology? – Related Questions
What are the main compartments of drug distribution?
In humans and related organisms, there are five major body compartments: the blood plasma, interstitial fluids, fat tissues, intracellular fluids, and transcellular fluids, the latter of which includes fluids in the pleural (peritoneal) cavity.
Which type of drugs are distributed?
Based on the molecular structure, drugs have variable distribution in different types of tissues such as fat, muscle, and brain. Unlike other tissues, the brain and testes are unique, as they contain membrane barriers making a drug significantly less susceptible to distribution.
How does Lipophilicity affect drug distribution?
Lipophilicity is an important physicochemical parameter that contributes to the absorption, distribution, metabolism, excretion, and toxicity of a drug. This often leads to compounds that have a high rate of metabolism, leading to poor solubility, high turn-over, and low absorption.
How does body size affect drug distribution?
The main factors that affect the tissue distribution of drugs are body composition, regional blood flow and the affinity of the drug for plasma proteins and/or tissue components. Obese people have larger absolute lean body masses as well as fat masses than non-obese individuals of the same age, gender and height.
How does body weight affect drug distribution?
In obese individuals, blood flow to fat is even poorer. Obese individuals are also likely to have a degree of heart failure which further decreases blood flow. This makes their fat a large compartment of potential distribution for lipophilic drugs which fills gradually, and then becomes a slowly emptying reservoir.
Is drug distribution reversible?
Distribution is a reversible process of movement of drugs from and to the site of measurement, typically the plasma or blood. Elimination comprises metabolism and excretion, and represents the total irreversible loss of the drug from the body.
How does disease state affect drug distribution?
Pathological states may affect the binding of drugs to plasma proteins, mainly human serum albumin and alpha 1 acid glycoprotein. The resulting modifications in the free fraction of the drug can cause a change in the volume of distribution.
What characteristic of a drug may allow it to cross the blood brain barrier?
Drug characteristics that are favorable for crossing the BBB are therefore high lipophilicity, small size and molecular weight, and low hydrogen-bonding potential (i.e., the drug is unionized at physiologic pH). Figure 1. Schematic of blood:brain barrier (BBB), brain parenchyma, and stroma.
Which drug has the highest volume of distribution?
Some drugs (e.g. tolbutamide, phenytoin, gentamicin, warfarin) are known to have small volumes of distribution (0.1–1 L/kg) while others (e.g. meperidine, propranolol, digoxin) are known to have large volumes of distribution (1–10 L/kg).
Which is the major process of absorption for more than 90% of drugs?
Passive diffusion or non-ionic diffusion is considered as the major absorption process for more than 90% of drugs (see figure 3). It is the movement of the drug molecule from a region of higher concentration to a region of lower concentration.
How drug distribution is affected by blood flow?
After a drug enters the systemic circulation, it is distributed to the body’s tissues. Distribution is generally uneven because of differences in blood perfusion, tissue binding (eg, because of lipid content), regional pH, and permeability of cell membranes.
What are different barriers in drug distribution?
These barriers may be composed of endothelial (e.g., blood–brain barrier) or epithelial cells (e.g., placental), or combinations of those cells working in concert to form a significant obstacle to drug passage into selective organs or tissues.
Where does drug absorption occur?
However, whether a drug is acidic or basic, most absorption occurs in the small intestine because the surface area is larger and membranes are more permeable (see Oral Administration ).
What is a drug distribution charge?
What is drug distribution? A charge for distributing drugs is based on a person transferring, selling, importing or moving in any way a controlled substance such as heroin, meth or cocaine. Yet such a charge doesn’t mean you must be caught in the act of selling or distributing such drugs.
How drugs are processed in the body?
Drugs undergo four stages within the body: absorption, distribution, metabolism, and excretion. After a drug is administered, it is absorbed into the bloodstream. The circulatory system then distributes the drug throughout the body. Then it is metabolized by the body.
How do you know if a drug is lipophilic?
Lipophilicity can be measured by the distribution of a drug between the organic phase, which is generally n-octanol pre-saturated with water, and the aqueous phase, which is generally water pre-saturated with n-octanol.
Why is lipophilicity of a drug important?
Lipophilicity is a physicochemical property of crucial importance in medicinal chemistry. On the molecular level it encodes information on the network of inter- and intramolecular forces affecting drug transport through lipid structures as well as drug’s interactions with the target protein.
What organ Cannot eliminate lipophilic drugs?
Lipophilic drug molecules are not directly excreted from the kidney. Only after they are metabolized into more hydrophilic molecules, can they be excreted through the kidneys into the urine. Drugs and their metabolites are also excreted into bile. This is usually mediated by protein transporters.
How does weight affect drug effectiveness?
Changes in body weight can influence the amount of medicine you need to take and how long it stays in your body. The circulatory system may slow down, which can affect how fast drugs get to the liver and kidneys.
What happens when an obese person is given lipophilic drug?
With lipophilic drugs (e.g., barbiturates, benzodiazepines), this parameter is significantly increased, explaining the prolongation of the plasma elimination half-life. For drugs that are almost equally soluble in water and oil (methyl xanthines, aminoglycosides), the V is slightly increased in the obese.
Why is fatty tissue important in drug distribution?
Because fat is poorly perfused, equilibration time is long, especially if the drug is highly lipophilic. Accumulation of drugs in tissues or body compartments can prolong drug action because the tissues release the accumulated drug as plasma drug concentration decreases.