In this powerpoint the distribution process of drugs and various factors that alters drug distribution is discussed..

1. ASIYABI.M
ASSISTANT PROFESSOR
DEPARTMENT OF PHARMACOLOGY

2. DEFINITION

4. VOLUME OF DISTRIBUTION
 Varying concentration of drug reaches different organs
and tissues of the body. The process of diffusion is consider
as complete, at the distribution equlibrium.
 At this stage difference tissues and organ containing
varying concentration of drug that can be determined by
the volume of tisssues in which drug is present.
 So, different body tissues and organs have different
concentration of drug.
 The physiological meaning of volume of distribution is
not clear.But there is constant reletionship between
Amount of drug in the body (X) and the concentration of
drug in plasma (C).

5. APPARENT VOLUME OF DISTRIBUTION
Hypothetical volume of body fluid into which drug is
dissolved or distributed it is named as Apparent
volume.

6. FACTOR EFFECTING DRUG DISTRIBUTION
1. Age: Distribution varies with difference in:
Total body content: It is maximum in infants.
Fat content: Greater in infants and in elder ones.
Skeletal muscles: Less in infants and elderly
people.
Organic composition: poorly developed blood
brain barrier, low myelin content and high cerebral
bloog flow are stated in infants causing greater drug
penetration in the brain.

7. Pregnancy : Growth of uterus, placenta and foetus
raise volume for drug distribution,In pregency . Drug
may also get distributed in foetus which act as separate
compartments. Plasma and ECF volume also increase
but albumin content reduced.
Obesity: High Adipose tissue content result to low drug
distribution and perfusion. High fatty acid content
alter the binding property of acidic drugs.
DIET: Fat rich diet increase free fatty acid
concentration in the blood that affects binding of
acidic drugs. Example: NSAID,Albumin.

8. Disease states: Drug distribution is severely affected in
diseased conditions, such as;
 Alteration in albumin and other drug-protein
concentration.
 Reduced or alter perfusion to organs and tissues.
 Alteration in tissue Ph.
In case of patient of encephalitis and meningitis, the
blood-brain barrier become more palatable, therefore
concentration of the ionic antibiotics (penicillin G
and ampicillin) increase in tissue of brain.
Drug interaction: Two or more drug administered
together compete for binding site and tend to replace
each other, and a free drug may cause lethal effect.