Farmacologia: Antibioticos: PENICILINAS

Introduction to Antibiotics: Penicillins

In this section, the discussion revolves around the introduction of antibiotics, specifically focusing on penicillins and their significance in pharmacology.

Discovery and Importance of Penicillins

• Penicillin, a bactericide discovered in 1928 by Alexander Fleming, revolutionized medicine by accidentally lysing bacteria cultures contaminated with a fungus.

Mechanism of Action of Penicillins

• Penicillins inhibit peptidoglycan synthesis by targeting the peptide glycan essential for bacterial cell wall formation, leading to bacterial destruction.

Composition and Resistance to Penicillins

• The chemical formula of penicillins includes key components like thiazolidine ring and beta-lactam ring crucial for biological activity against bacteria.

• Bacteria develop resistance mechanisms like beta-lactamase production to deactivate the active component of penicillins, rendering them ineffective.

Bacterial Cell Wall Structure and Interaction with Penicillins

This section delves into the structure of bacterial cell walls and how penicillins interact with specific components to exert their antibacterial effects.

Bacterial Cell Wall Morphology

• Gram-positive bacteria have thicker peptidoglycan layers compared to gram-negative bacteria, aiding in absorbing dyes due to more extensive wall structures.

Peptidoglycan Components

• Peptidoglycan consists of molecules like N-acetylglucosamine and N-acetylmuramic acid linked by amino acids such as lysine, forming cross-linked structures crucial for bacterial integrity.

Transpeptidase Enzyme Function

• Transpeptidase enzymes facilitate cross-linking within peptidoglycan layers, enabling penicillin binding that disrupts bacterial cell wall synthesis through enzymatic deactivation.

Understanding Penicillins and Antibiotic Resistance

In this section, the discussion revolves around the differences between gram-negative and gram-positive bacteria in terms of their cell wall structure, the effectiveness of penicillins against these bacteria, and the development of antibiotic resistance mechanisms.

Differences Between Gram-Negative and Gram-Positive Bacteria

• Gram-negative bacteria have a thin layer of peptidoglycan in their cell wall, making them less susceptible to certain antibiotics like penicillins.

• Gram-negative bacteria possess an outer membrane that provides them with various qualities such as drug resistance, immunity evasion, and metabolic advantages.

Antibiotic Resistance Mechanisms

• Gram-negative bacteria have developed defense mechanisms like beta-lactamase enzymes, mutations in penicillin-binding proteins, and efflux pumps to expel antibiotics.

• Penicillins are classified into natural and semi-synthetic types. Natural penicillins include Penicillin G (oral) and Penicillin V (discontinued), while semi-synthetic ones are designed to combat beta-lactamase.

Classification of Penicillins

This section delves into the classification of penicillins based on their spectrum of activity, administration routes, duration of action, and specific targets against different bacterial strains.

Types of Penicillins

• Penicillins can be categorized as narrow-spectrum (effective against specific bacteria), broad-spectrum (targeting a wide range), or anti-pseudomonal (aimed at Pseudomonas aeruginosa).

• Semi-synthetic penicillins resistant to beta-lactamase include Oxacillin and Cloxacillin with a 6-hour duration. Broad-spectrum variants like Amoxicillin and Ampicillin act against gram-negatives for 8-6 hours.

Administration and Absorption Considerations

This part focuses on how food intake impacts the absorption of penicillins in the body, emphasizing timing for optimal effectiveness.

Food Interaction with Penicillins

• Most penicillins should be taken two hours before or after meals due to reduced availability in acidic environments except for Amoxicillin which can be consumed with food.

Antibiotics: Penicillins and Adverse Effects

In this section, the speaker discusses the effectiveness of penicillin, its elimination from the body, indications for use, classification, adverse effects, and precautions associated with penicillins.

Effectiveness and Elimination of Penicillins

• Penicillin is only effective in about 5% of cases such as meningitis or prostate infections. Other antibiotics are needed for the remaining cases.

• Penicillins are primarily eliminated through biliary and renal pathways. Special care is required when administering penicillins to individuals with compromised kidney function.

Classification and Mechanism of Action

• Penicillin is an antibiotic that targets susceptible bacteria but has no effect on viruses, fungi, or parasites. It mainly acts against gram-positive bacteria and sometimes gram-negative bacteria with broad spectrum activity like amoxicillin and ampicillin.

• The FDA classifies penicillins as type B drugs, indicating they can be used during pregnancy without evidence of harm to the fetus. However, all medications have potential side effects.

Adverse Effects and Precautions

• Common adverse effects of penicillins include allergies, angioedema, renal function alterations (nephritis), neutropenia (temporary decrease in defenses), and colitis pseudomembranous (gastrointestinal infection).

• Prolonged use of antibiotics like penicillins can lead to Clostridium difficile infection causing pseudo-membranous colitis. Caution is advised regarding long-term or varied antibiotic usage to prevent such complications.

Allergic Reactions and Cautions

• Over 30% of the global population may be allergic to penicillin leading to skin reactions, gastrointestinal issues, or respiratory problems necessitating immediate discontinuation of the medication. Severe allergic reactions like Stevens-Johnson syndrome can occur due to penicillin administration.