Question

can you explain the two aspects of pharmacodynamics in detail?

Answer 1

Pharmacodynamics is the effect of drug on the body

1. Mechanism of action
   1. It is the method by which a drug exerts its effect.
   2. It may physically interact with its substrate - activated charcoal adsorbs poison
   3. It may chemically react with the drug. Antacid like aluminium hydroxide react with gastric HCl and neutralize it.
   4. It may act of specific receptors. Epinephrine acts on adrenergic receptors (alpha and beta receptor)
   5. It may block the action of drug. Atropine blocks the action of acetylcholine choline.
   6. Enhance the secretion of hormones - glimepiride - acts on the beta cells of langerhans and promote the secretion of insulin.
2. Drug and drug interactions
   1. When 2 or more drugs are administered to the same patient, there is a possibility that one drugs may affect the action/ concentration of another drug.
   2. Cytochrome enzyme induction - a drug may increase the activity of hepatic cytochrome enzyme.
   3. These enzymes play an important role in degradation of the drug.
   4. So if this enzyme's activity js enhanced it will reduce the blood levels of the other drug.
   5. Thus, reducing it effect.
   6. Example - Rifampicin induces cytochrome enzyme. If warfarin is also administered to the patient, it blood levels will reduce.
   7. Some drugs may displace another drug from it binding site on plasma proteins.
   8. Example - sulphonamides displace bilirubin from albumin.
   9. Certain drugs may inhibit cytochrome enzyme and enhance the action of other drugs.