Question

What does a drug need to be soluble in water?

What does a drug need to be permeable to tissues?

What will happen if the solubility of my drug changes over time?

Answer 1

1. When any drug intake in body orally or any rout, absoption, distribution, metabolism and elimination take place like intake of food. Drug possess saivary action, acidic action in stomach and basic action in intestine.

2. For absorption, it must absorb across the cell membrane, and distribute through blood (water soluble),since cell membrane has polar and non-polar end therefore absorbs through cell membrane and will be enter in blood and must be soluble in water.

3. The drug need to be permeable to tissue, for this purpose the drug can not be make purely hydrophilic, if purely hydrophilic than will not cross blood-brain barrier and eliminate as such through urine (water soluble).

4. But if 100% hydrophobic, lipid soluble than it binds with tissues and not be permeable and not enter in blood system and may cause reaction or side effect or release after sometimes.

5. Therefore when any drug make, it has some lipophilicity as well as hydrophilicity therefore cross through cell membrane of alimentry canal and after absorption enter in blood.

6. The solubility of drug if changes over time, it affact its partition coefficient means lipophilicity as wellas hydrophilicity and may cause change in absorption and distribution,ifhydrophilicity increases,means more soluble in water than it difficult to absorbs or difficult to cross lipidmembrane of body wall and eliminate through water medium (urinal) without showing mechanismof action (very low conc.showing)