Question

1. Why do tissues differ in their distribution of drugs?
2. What is volume of distribution and how do you calculate it?
3. How might a drug’s volume of distribution be altered in the case of a person who is obese?
4. How does decreased kidney function or dehydration affect volume of distribution and drug concentration in blood

Answer 1

#. 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,that's why tissue differin their distribution of drugs .

#. The volume of distribution of a drug gives information on its distribution in the body. The Vd is calculated as the ratio of the dose present in the body and its plasma concentration.

#. The volume of distribution varies the most with percent body fat, an issue in overweight and obese patients. It can also vary with age, as the proportion of each body compartment changes with the aging process. Therefore, dosage may need to be modified in obese or elderly patients.

#. Plasma protein binding of many drugs is impaired in patients with renal disease. This often results in a larger apparent volume of distribution and a larger clearance of the drug compared to that observed in patients with normal renal function.