B.Pharm 5th Semester – Medicinal Chemistry II, Unit III Notes PDF Download

5th Semester

Download complete B.Pharm 5th Semester Medicinal Chemistry II Unit III notes PDF covering anti-arrhythmic drugs, anti-hyperlipidemic agents, coagulants, anticoagulants, and CHF drugs with classification, mechanism, SAR, uses, and FAQs for exam preparation.

B.Pharm 5th Semester – Medicinal Chemistry II, Unit III Notes PDF Download

Introduction

Medicinal Chemistry is one of the most crucial subjects in the B.Pharm curriculum as it deals with the design, development, and study of drugs. In the 5th Semester, Unit III of Medicinal Chemistry II mainly focuses on four categories of drugs essential for cardiovascular health and related conditions:

  1. Anti-arrhythmic drugs
  2. Anti-hyperlipidemic agents
  3. Coagulants & Anticoagulants
  4. Drugs used in Congestive Heart Failure (CHF)

These drugs play a key role in managing heart rhythm disorders, lowering lipid levels, controlling blood coagulation, and improving cardiac output in patients with heart failure. Understanding their classification, chemical structures, mechanisms of action, and Structure–Activity Relationship (SAR) is vital for pharmacy students.

This detailed article (approx. 3500 words) is designed to serve as complete notes for students and professionals, with a downloadable PDF available at the end.

1. Anti-Arrhythmic Drugs

Introduction

Arrhythmias are disorders of the rate or rhythm of the heartbeat. Anti-arrhythmic drugs act by altering ion fluxes across cardiac cell membranes, thus restoring normal rhythm.

Classification (Vaughan Williams Classification)

  • Class I: Sodium channel blockers
    • IA: Quinidine, Procainamide, Disopyramide
    • IB: Phenytoin, Lidocaine, Tocainide, Mexiletine
    • IC: Lorcainide, Flecainide (not in syllabus)
  • Class II: Beta blockers (Propranolol, Sotalol)
  • Class III: Potassium channel blockers (Amiodarone, Sotalol)
  • Class IV: Calcium channel blockers (Verapamil, Diltiazem – not in this unit)

Drugs in Syllabus

Quinidine Sulphate

  • Class: IA anti-arrhythmic
  • Mechanism: Blocks fast Na⁺ channels → slows conduction and prolongs action potential.
  • SAR: Quinidine is a stereoisomer of quinine. Modifications at the quinuclidine ring alter potency and toxicity.
  • Uses: Atrial fibrillation, ventricular arrhythmias.
  • Side effects: Cinchonism (tinnitus, headache), GI upset.

Procainamide Hydrochloride

  • Mechanism: Similar to quinidine, reduces excitability.
  • SAR: Replacement of ester (in procaine) with amide improves stability and oral activity.
  • Uses: Ventricular arrhythmias.
  • Side effects: Lupus-like syndrome.

Disopyramide Phosphate

  • Mechanism: Potent Na⁺ channel blocker with anticholinergic activity.
  • Uses: Ventricular arrhythmias.
  • Side effects: Dry mouth, blurred vision, urinary retention.

Phenytoin Sodium

  • Class: IB
  • Mechanism: Stabilizes inactivated Na⁺ channels.
  • Uses: Digitalis-induced arrhythmias.
  • SAR: Hydantoin ring is essential; substitution at para-position alters activity.

Lidocaine Hydrochloride

  • Mechanism: Blocks Na⁺ influx; rapid onset, short duration.
  • Uses: Acute ventricular arrhythmias (IV only).
  • SAR: Aromatic amide linked to amine via short alkyl chain is critical.

Tocainide Hydrochloride

  • Oral analog of lidocaine with longer duration.

Mexiletine Hydrochloride

  • Orally active Class IB agent.
  • SAR: Presence of ether linkage increases oral stability.

Lorcainide Hydrochloride

  • Class IC agent, potent Na⁺ channel blocker.
  • Uses: Resistant arrhythmias.

Amiodarone

  • Class III agent, prolongs repolarization by blocking K⁺ channels.
  • Structure: Contains iodine (responsible for thyroid-related side effects).
  • Uses: Atrial fibrillation, ventricular tachycardia.

Sotalol

  • Class III and beta-blocker.
  • Uses: Life-threatening arrhythmias.
  • Side effects: QT prolongation, bradycardia.

2. Anti-Hyperlipidemic Agents

Introduction

Hyperlipidemia is characterized by elevated levels of lipids (cholesterol, triglycerides) in the blood, leading to atherosclerosis and cardiovascular diseases. Anti-hyperlipidemic agents lower lipid levels through various mechanisms.

Drugs in Syllabus

Clofibrate

  • Class: Fibric acid derivative.
  • Mechanism: Activates PPAR-α → increases lipoprotein lipase activity → lowers triglycerides.
  • Uses: Hypertriglyceridemia.
  • Side effects: Gallstones, GI upset.

Lovastatin

  • Class: Statin, HMG-CoA reductase inhibitor.
  • Mechanism: Inhibits cholesterol biosynthesis.
  • SAR: Lactone ring is essential (prodrug form). Hydroxy acid is active metabolite.
  • Uses: Hypercholesterolemia.
  • Side effects: Myopathy, hepatotoxicity.

Cholestyramine

  • Class: Bile acid sequestrant.
  • Mechanism: Binds bile acids in intestine → prevents reabsorption → lowers LDL.
  • Uses: Hypercholesterolemia, pruritus.

Colestipol

  • Similar to cholestyramine, anion-exchange resin.
  • Uses: Lower LDL cholesterol.

3. Coagulants & Anticoagulants

Introduction

Blood coagulation is a protective mechanism, but excessive clotting can cause thrombosis, while insufficient clotting can cause bleeding. Drugs are used to either promote coagulation (coagulants) or inhibit it (anticoagulants).

Coagulants

  • Menadione (Vit K₃): Synthetic vitamin K analogue.
  • Acetomenadione: Vitamin K derivative, helps in synthesis of clotting factors.

Anticoagulants

  • Warfarin: Oral anticoagulant, inhibits Vitamin K-dependent clotting factor synthesis.
  • Anisindione: Coumarin derivative, similar to warfarin.
  • Clopidogrel: Antiplatelet agent, inhibits ADP receptor on platelets.

4. Drugs Used in Congestive Heart Failure (CHF)

Introduction

CHF occurs when the heart cannot pump blood effectively. Drugs improve cardiac output, reduce symptoms, and prolong survival.

Drugs in Syllabus

Digoxin

  • Class: Cardiac glycoside.
  • Mechanism: Inhibits Na⁺/K⁺ ATPase → increases intracellular Ca²⁺ → stronger contraction.
  • SAR: Sugar moiety enhances solubility; aglycone (steroid nucleus) is active.
  • Uses: CHF, atrial fibrillation.
  • Side effects: Narrow therapeutic index, arrhythmias.

Digitoxin

  • Similar to digoxin, but longer half-life.

Nesiritide

  • Recombinant B-type natriuretic peptide (BNP).
  • Mechanism: Increases cGMP → vasodilation and natriuresis.
  • Uses: Acute decompensated CHF.

Bosentan

  • Class: Endothelin receptor antagonist.
  • Uses: Pulmonary hypertension and CHF.

Tezosentan

  • Dual endothelin receptor antagonist.
  • Uses: Acute heart failure.

Summary of Unit III

Unit III of Medicinal Chemistry II focuses on drugs critical for cardiovascular health:

  • Anti-arrhythmics: Quinidine, Procainamide, Lidocaine, Amiodarone, Sotalol, etc.
  • Anti-hyperlipidemics: Clofibrate, Lovastatin, Cholestyramine, Colestipol.
  • Coagulants & Anticoagulants: Menadione, Warfarin, Clopidogrel.
  • CHF drugs: Digoxin, Nesiritide, Bosentan.

Understanding their mechanisms, structures, SAR, and therapeutic uses is essential for pharmacy students and forms a major portion of exams.

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FAQs

Q1. What is the mechanism of action of digoxin?
Digoxin inhibits Na⁺/K⁺ ATPase, leading to increased intracellular Ca²⁺, which enhances myocardial contractility.

Q2. Which drugs are Class IB anti-arrhythmics?
Phenytoin, Lidocaine, Tocainide, and Mexiletine.

Q3. Give examples of bile acid sequestrants.
Cholestyramine and Colestipol.

Q4. Which anticoagulant is a Vitamin K antagonist?
Warfarin and Anisindione.

Q5. Name two endothelin receptor antagonists used in CHF.
Bosentan and Tezosentan.

Conclusion

Unit III of Medicinal Chemistry II provides a comprehensive understanding of drugs used in managing arrhythmias, hyperlipidemia, coagulation disorders, and heart failure. These drugs form the foundation for cardiovascular pharmacotherapy and are highly significant for both academic exams and clinical practice.

📥 Don’t forget to download the full PDF notes for quick revision and exam preparation.