Drug distribution

• Explain the importance of drug distribution and factors affecting rate of drug distribution • Distinguish between perfusion and permeability-limited distribution • Define volume of distribution and interpret this pharmacokinetic parameter • Understand the role of plasma protein binding in drug distribution

what is the Rate of drug distribution

The speed at which a drug spreads throughout the body.

what does rate of drug distribution depend on?

• Tissue perfusion

• Permeability of tissue membranes

• Physiochemical properties of the drug

• Binding of drug to plasma proteins - only unbound drug crosses membrane

• Binding to acidic phospholipids in tissue membranes

what is Perfusion limited distribution

When the rate of blood flow through tissues determines the distribution of a drug.

what is Permeability limited distribution

Distribution of a drug is restricted by the ability of the drug to pass through membranes.

what is Apparent volume of distribution

The theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the observed blood concentration.

how can apparent volume of distribution (v) be calculated

•  V = concentration (c) / amount of drug in body at equilibrium (A)

Factors affecting volume distribution

• Affinity of drugs to plasma proteins, blood cells, and tissue components influencing the volume of distribution.

• Acidic drugs have strong affinity plasma proteins

• Basic drugs have a higher volume of distribution

• Monoclonal antibodies generally low volume distribution

Clinical relevance of volume of distribution

Important for determining the initial loading dose and subsequent maintenance dose of a drug.

Plasma Protein binding

Process where drugs bind to plasma proteins, affecting the distribution and elimination of the drug.

what does fu stand for

fraction of unbound drug

how to calculate fraction of drug which is bound?

1- fraction unbound (fu)