Pharmacology Drug Action and Mechanisms

Study Notes

Drugs bind to the body's control systems, known as targets.
Target examples include receptors, ion channels, enzymes, and carrier molecules (transporters).

Signal transduction involves the process where a signal is transmitted through a cell.
This process often involves receptors and the activation of second messengers, such as cAMP (cyclic AMP).

Receptors can be classified based on their response to ligands.
Agonists: Ligands that activate the receptor, triggering a cellular response.
Antagonists: Ligands that block the receptor, preventing its activation and preventing a response.

Agonists, when bound to a receptor, mimic the natural ligand and initiate a cellular response.
Antagonists, when bound, block the receptor, preventing activation and interfering with the natural ligand’s activity.
Partial agonists: Exhibit a weaker response compared to full agonists.

Receptors are located on various parts of the cell, including the cell membrane, cytoplasm, and nucleus.
They mediate different cellular functions, such as cell signaling, ion transport, and gene expression.

G-protein-coupled receptors (GPCRs): An important class of receptors involved in signal transduction.
Tyrosine kinase-linked receptors: mediate signaling pathways involving tyrosine phosphorylation.
These pathways involve second messengers, such as cAMP, calcium, and inositol triphosphate (IP3), which amplify the signal and regulate downstream cellular processes.
Ligand-gated ion channels: Receptors that directly control ion flow across cell membranes, affecting electrical signaling.

Directly activate: Drugs that directly activate or inhibit the target through binding.
Affect second messengers: Drugs that modify the levels or activity of second messengers to impact signaling pathways.
Modify enzyme activity: Drugs can inhibit or activate specific enzymes, affecting their function.
Alter transporter function: Drugs can influence the movement of substances across cell membranes by inhibiting or enhancing transporter activity.

Drug bioavailability: The extent to which a drug reaches systemic circulation after administration.
Drug metabolism: The process of modifying the drug's structure, often leading to inactivation and elimination.
Drug elimination: The removal of the drug from the body via various pathways like urine, feces, and exhalation.

Understanding drug mechanisms is crucial for:
- Developing effective therapies
- Predicting and managing drug interactions
- Optimizing drug dosing and administration
- Understanding drug resistance and adverse effects.