Question

identify one body system and explain its significant effects on drug response

Answer 1

Hepatobiliary system - this system consist of liver, gallbladder and bile ducts.

The liver impacts the drug response in the following ways:

1. First pass metabolism
   1. When a drug is absorbed orally it enters the small intestine.
   2. From the small intestine it is absorbed into the portal circulation.
   3. From the portal circulation, drug enters the liver.
   4. In the liver, the drug is metabolized.
   5. This reduces it activity and therefore reduces its response.
2. Pro-drug
   1. Some drugs are available in an prodrug form. These drugs have reduced activity or no activity.
   2. When acted upon my liver enzyme, these prodrugs get converted to active drug.
   3. Example - Codeine is acted upon by cytochrome-P450 CYP2D6 to form morphine.
3. Enzyme induction -
   1. When 2 different drugs are administered together, they can interfere with each other action.
   2. Hepatic cytochrome-P450 enzymes metabolize drugs.
   3. They enzymes can be influenced by exogenous administered drugs.
   4. If a drug (example - rifampicin) induces cytochrome enzyme, it will increase the metabolism of another drug (example - warfarin)
   5. This reduces the activity of the drug.
4. Enzyme inhibition
   1. Some drugs inhibit hepatic cytochrome-P450 enzyme.
   2. Example - chloramphenicol, erythromycin.
   3. If another drug administered alone with these drugs, the activity of the that drug increases.