Anti-Infective Agents PDF

PHARMA PHARMACOLOGY: ANTI-INFECTIVE AGENTS Anti-Infective Agents - Definition: Drugs that treat and prevent infections from microorganisms (bacteria, viruses, fungi, parasites) by targeting their survival mechanisms. - Selective Action: Target foreign organisms with minimal harm to human cel...

PHARMA PHARMACOLOGY: ANTI-INFECTIVE AGENTS Anti-Infective Agents - Definition: Drugs that treat and prevent infections from microorganisms (bacteria, viruses, fungi, parasites) by targeting their survival mechanisms. - Selective Action: Target foreign organisms with minimal harm to human cells. - Protecting the Host: Supports the immune system to help recover from infections. - Combating Infections: Essential for treating and preventing the spread of infectious diseases. Types of Anti-Infective Therapy 1. Antibiotics: Kill or inhibit bacteria to treat infections. 2. Antifungals: Disrupt growth of fungi to treat infections. 3. Antivirals: Interfere with virus replication to treat infections. 4. Anti-protozoans: Treat protozoan infections. 5. Anti-helmintics: Treat worm infections. 6. Anti-neoplastics: Target cancer-causing microorganisms. Mechanism of Action (MOA) - Targeting Invaders: Disrupt functions of invading organisms to prevent reproduction and cause cell death. - Disrupting Normal Function: Interfere with pathogen activities without harming host cells. - Selective Toxicity: Specifically affect pathogen cells only. Anti-Infective Activity - Narrow-Spectrum: Effective against a limited range of specific microorganisms. - Broad-Spectrum: Effective against a wide variety of microorganisms. Microorganisms Develop Resistance - Enzyme Deactivation: Bacteria produce enzymes that deactivate antibiotics. - Altering Cell Permeability: Changes prevent drug entry into cells. - Modifying Binding Sites: Alters drug targets to block action. - Producing Antagonists: Microorganisms produce chemicals that neutralize drug effects. Preventing Resistance - Proper Dosage: Doses must eradicate resistant microorganisms. - Combating Resistance: Maintain appropriate dosages and treatment durations. - Patient Compliance: Adherence to full treatment is critical. Usage Guidelines - Prescribe Appropriately: Use anti-infectives only for specific infections. - Cautious Usage: Avoid indiscriminate use to prevent resistance. - Follow Guidelines: Adhere to established protocols for responsible use. Treatment of Systemic Infections - Identification of the Pathogen: Culture samples to determine microorganisms causing infection. - Sensitivity of the Pathogen: Testing to find effective drugs. - Combination Therapy: Using multiple drugs to enhance effectiveness and reduce side effects. Combination Therapy: Additional Benefits - Synergistic Effects: Increased efficacy with combined drugs. - Delayed Resistance: Preserves effectiveness of anti-infectives. - Broader Spectrum: Addresses polymicrobial infections comprehensively. Adverse Reactions to Anti-Infective Therapy 1. Kidney Damage: Common with drugs metabolized by the kidneys; hydration prevents accumulation. 2. Gastrointestinal Toxicity: Side effects include nausea and diarrhea. 3. Neurotoxicity: Affects cranial nerve VIII, causing dizziness and hearing loss. 4. Hypersensitivity Reactions: Immune responses can lead to severe reactions. 5. Superinfections: Disruption of normal flora can allow opportunistic infections. Prophylaxis Travel Prophylaxis: Preventive measures for infections in endemic areas. Surgical Prophylaxis: Antibiotics to prevent post-operative infections. Cardiac Conditions: Prophylaxis for those at risk of bacterial endocarditis. Antibiotics/Antibacterial - Bacteriostatic Drugs: Inhibit bacterial growth. - Bactericidal Drugs: Kill bacteria directly. Goal of Antibiotic Therapy Decrease Bacterial Population: Reduce bacteria for immune system management. Support Immune System: Assist in eliminating remaining pathogens. Prevent Complications: Effective treatment prevents infection worsening. Bacterial Classification Gram-Positive Bacteria: Retain stain; associated with respiratory infections. Gram-Negative Bacteria: Lose stain; often resistant and linked to GI and urinary infections. Aminoglycosides - Powerful Antibiotics: Treat serious infections from gram-negative bacteria. - Indications: For severe infections like pneumonia and sepsis. - Examples: Amikacin: Used for serious infections. Gentamicin: Covers a wide range of infections. Kanamycin: Used for hepatic coma treatment. Neomycin: Suppresses GI bacteria. Streptomycin: Used in tuberculosis treatment. Tobramycin: Treats ocular infections. Cephalosporins - MOA: Bactericidal; disrupt cell wall synthesis. - Generations: 1. First-Generation: Effective against gram-positive and some gram-negative (e.g., E. coli). - Examples: Cefadroxil, Cefazolin, Cephalexin. 2. Second-Generation: Broader activity including H. influenzae. - Examples: Cefaclor, Cefuroxime, Cefprozil. 3. Third-Generation: More potent against gram-negative; weaker against gram-positive. - Examples: Cefdinir, Ceftriaxone, Ceftazidime. 4. Fourth-Generation: Active against resistant strains. - Examples: Cefepime, Cefditoren. - Adverse Reactions: Disulfiram-like reactions with alcohol. Fluoroquinolones Broad Spectrum: Effective against various bacteria. - MOA: Inhibit bacterial DNA enzymes. - Indications: For infections like UTIs and respiratory infections. - Examples: Ciprofloxacin: For UTIs and anthrax prevention. Levofloxacin: Treats respiratory infections. Gemifloxacin: For community-acquired pneumonia. Macrolides - MOA: Inhibit protein synthesis in bacteria. - Indications: Effective against respiratory and STIs. - Examples: Erythromycin: Treats a variety of infections. Azithromycin: Long half-life, for respiratory infections. Clarithromycin: Effective against respiratory infections and mycobacteria. Tetracyclines - MOA: Inhibit protein synthesis. - Indications: Effective for rickettsiae and acne. - Examples: Tetracycline: Treats various infections. Doxycycline: For traveler's diarrhea and STIs. Minocycline: Drug of choice for meningococcal carriers. Antituberculosis Drugs - First-Line Drugs: Isoniazid (INH): Inhibits mycolic acid synthesis. Rifampin: Alters bacterial RNA activity. Ethambutol: Inhibits cellular metabolism. Pyrazinamide: Exhibits both bactericidal and bacteriostatic properties. - Second-Line Drugs: Ethambutol: Inhibits metabolism. Pyrazinamide: Bactericidal and bacteriostatic. - Third-Line Drugs: Capreomycin: MOA not fully understood; for resistant TB. Cycloserine: Inhibits cell wall synthesis. - Major Side Effects: Rifampicin: Causes red-orange secretions. Isoniazid: Peripheral neuritis. Pyrazinamide: Increases uric acid. Ethambutol: Can cause visual problems. Leprostatic Drugs - Dapsone: Main treatment for leprosy; emerging resistant strains. Monobactam Antibiotics Aztreonam: Effective against gram-negative bacteria. - Indications: Treat UTIs, skin infections, and intra-abdominal infections. Carbapenems - Class Overview: Broad-spectrum antibiotics effective against many resistant bacteria. - Examples: Imipenem: Used for severe infections; combined with cilastatin. Meropenem: For various infections including resistant strains. Ertapenem: Effective for a range of infections; not for Pseudomonas. Doripenem: Treats severe infections with resistant bacteria.