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V Sem Medicinal Chemistry MOA

MedChem Master - Interactive MOA Guide

MedChem Pro

Mechanisms of Action

Detailed study guide for Medicinal Chemistry. Explore molecular pathways, receptor interactions, and drug classifications.

UNIT I

Antihistamines & Anti-neoplastics

Antihistaminic Agents

Respiratory / GI
H1-Antagonists

Act as inverse agonists. Stabilize the inactive $H_1$ receptor conformation, preventing histamine-induced vasodilation and itching.


H2-Antagonists & PPIs

H2 blockers competitively inhibit binding on parietal cells. PPIs (Omeprazole) are prodrugs that form covalent bonds with $H^+/K^+$-ATPase.

Anti-neoplastic Agents

Oncology

Focuses on DNA integrity and cell division inhibition.

ALKYLATING

Attaches alkyl groups to $N_7$ Guanine, causing cross-linking and apoptosis.

VINCA ALKALOIDS

Bind to tubulin, inhibiting polymerization into microtubules (M-phase arrest).

UNIT II

CVD & Renal Agents

Anti-anginal Agents

Nitrates: Release NO → Stimulates Guanylyl Cyclase → $\uparrow$ cGMP → Dephosphorylation of Myosin → Vasodilation.

CCBs: Block inward $Ca^{2+}$ flux through L-type channels, reducing afterload and contractility.

Diuretics Classification

Loop Diuretics Inhibit $Na^+/K^+/2Cl^-$ cotransporter
Thiazides Inhibit $Na^+/Cl^-$ symporter
K-Sparing Aldosterone Antagonism or ENaC Blockade
UNIT III

Heart & Lipid Management

Cardiac Glycosides

Digoxin: Inhibits $Na^+/K^+$-ATPase → $\uparrow$ intracellular $Na^+$ → $\downarrow$ $Na/Ca$ exchange → $\uparrow$ $Ca^{2+}$ → Positive Inotropy.

Lipid Lowering

Statins: Competitive inhibition of HMG-CoA Reductase (the rate-limiting step in cholesterol synthesis).

UNIT IV

Endocrine System

Key: Most steroids work via intracellular receptors to modulate gene transcription.

PDE-5 Inhibitors

Block cGMP breakdown in corpus cavernosum → Persistent smooth muscle relaxation.

Antithyroid

Propylthiouracil inhibits thyroid peroxidase, blocking iodine organification.

UNIT V

Diabetes & Local Anesthetics

Antidiabetic Pathways

  • Sulfonylureas: Close ATP-sensitive $K^+$ channels → Depolarization → Insulin release.
  • Metformin: Activates AMPK → $\downarrow$ Gluconeogenesis.

Local Anesthetics (LA)

LAs bind to the internal surface of voltage-gated $Na^+$ channels. They stabilize the channel in an inactivated state, preventing $Na^+$ influx and effectively blocking the generation and conduction of nerve impulses.

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