Pharmacodynamics summarized notes, Lecture notes of Nursing

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Pharmacodynamics

Mutai Ben 22/11/

Lesson Objectives

• By the end of the lesson, the learner should be able to: i. Define pharmacodynamics ii. Explain Drug action (mode of action) iii. Describe drug interaction iv. Describe side effects, adverse effects

DRUG ACTION

• Drugs act on extracellular, cellular, or intracellular compartments
• The types of drug responses (effects) include:
  • Stimulation
  • Inhibition/Depression
  • Replacement
  • Irritation
  • Cytotoxic

1. ION CHANNELS

• Ion channels are passages in the cell membrane that selectively allow transit of particular ions (K, Ca, Na, Chloride channels)
• The main ones are i. Ligand gated channels ii. Voltage gated channels

2. ENZYMES

• These are protein molecules that accelerates chemical reactions. Drug molecules may inhibit or stimulate an enzyme to produce its effect.
• An example is captopril that inhibits Angiotensin converting enzyme (ACE), and Aspirin that inhibits Cyclooxygenase

4. RECEPTORS

• Receptors are the integral membrane proteins embedded in cell membranes (surface, cytoplasm, or nucleus) that receives signals or binds with ligands to initiate response or cell signaling. The functions of receptors include: - To propagate the regulatory signals - To amplify the signal - To integrate the intracellular and extracellular signal - To adapt short term and long term changes

Type i: Ligan Gated ion channels (ionotropic receptors )

• These are membrane proteins with similar structure to other ion channels and incorporate a ligand binding site (receptor) usually in the extracellular domain. Neurotransmitters mainly act on these sites e.g., GABA & nACh receptors

Type ii: G~protein coupled receptors (metabotropic)

• These are membrane receptors coupled to intracellular effector systems via a G ~ Protein. They include receptors for hormones and slow transmitters
• They mainly act by adenyl cyclase pathways, phospholipase C pathway, and ion channels

Type iv:

Kinase Linked