Question

Explain how oral-administered drugs can reach the target cells to exert the therapeutic effects（6 marks）

Answer 1

Once a drug is adminsitered

1. The drug (tablet/ capsule/ granules/ powder/ susoension/ emulsion) when administered orally with water reaches stomach.

2.In stomach the disintegration as well as dissolution of solid dosage form (tablet/ capsule/ granules) is observed due to presence of gastric fluid and water.

3. As soon as the drug is released from dosage form, it starts to absorb from fine capillaries found in stomach

4. The disintegration and dissolution of enteric cocate dosage form begins and completes ins small intestine.

5. The drug from stomach/ small intestine gain entry into systemic circulation/ blood. The availability of drug in blood/ site of action is termed as bioavailability.

6. A fraction of drug gets bound temporarily to proteins found in blood (sometimes proteins of tissues). This phenomenon is called as protein binding.

7. The drug is transported to site of action through blood.

For examples after absorption analgesics gain entry in blood and reach at the site of action. Interaction of analgesics with COX-2 enzymes porduces analgesic effect.

8. A drug gets metabolized after is shows its therapeutic effect (however, sometimes a drug can get metabolized before its onset of action).

9. The porcess of drug metabolism generally makes drug water soulble, these water soluble metabolites are excreted from body by urine (sometimes biile).