Page 25 - Pharmacology Mnemonics and Short Notes

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Drug Distribution

Process by which a drug reversibly leaves the circulation and enters the
interstitium and cells of the tissue.

Intracellular
compartment
Cell membrane
Interstitial compartment

Endothelium of capillary wall Extracellular
Intravascular (Plasma)

Compartment

Drugs are distributed to the different tissues and body fluids,
according to the compartmental models.

*One compartment model (intravascular)
 E.g. drugs with high molecular weight as heparin has Vd 3-4 L.

*Two compartment model (extracellular distribution)
 Drug with small molecular weight but ionized e.g. skeletal muscle
relaxants have Vd average of 14 L.
*Multicompartmental model (extracellular and intracellular

distribution)
 Drug with small molecular weight and lipid soluble as alcohol has

Vd average of 42 L.

*Selective distribution
 Some drugs have special affinity for specific tissue. e.g. calcium in
Contents bones and iodide in thyroid gland.

Pharmacology Mnemonics and Short Notes By Muhammad Ramzan Ul Rehman