Chemotherapeutics Introduction

Chemotherapeutics Overview

Introduction to Chemotherapeutic Drugs

• Chemotherapeutic drugs are utilized to eliminate both invading organisms and abnormal cells within the body.

• These drugs target microorganisms such as bacteria, viruses, and protozoans by altering cellular functions or disrupting integrity, leading to cell death or preventing reproduction.

Types of Chemotherapeutic Drugs

• Two main categories of chemotherapeutic drugs include anti-infectives and anti-neoplastics. Anti-infectives target foreign organisms while anti-neoplastics focus on cancerous cells.

• Anti-infectives encompass various drug types including antivirals and antibacterials, whereas anti-neoplastics are specifically designed for cancer treatment.

Key Terms in Chemotherapy

Understanding Bactericidal vs Bacteriostatic

• Bactericidal: Substances that cause the death of bacteria (e.g., penicillin).

• Bacteriostatic: Substances that inhibit bacterial replication without killing them directly; used for prophylaxis against infections.

Antibiotic Resistance

• Pathogens can adapt over time, resulting in antibiotic resistance where they become unaffected by specific drugs; adherence to prescriptions is crucial to prevent this issue.

Mechanisms of Action for Anti-Infectives

Selective Toxicity

• Most anti-infective agents lack total selective toxicity; they may affect human cells alongside pathogens due to their action on shared biological processes.

Mechanisms of Action

• Inhibition of bacterial cell wall synthesis leads to bactericidal effects (e.g., penicillins).

• Alteration of membrane permeability results in bacteriostatic effects, preventing bacterial reproduction (e.g., antifungals).

Therapeutic Goals and Immune Response

Reducing Pathogen Load

Therapeutic Challenges in Immunocompromised Patients

Importance of Infection Prevention

• The goal of therapy for immunocompromised patients is to effectively use anti-infectives, which can be challenging due to the lack of inflammatory or immune response in these individuals.

• Preventing infections is crucial for these patients, alongside ensuring proper nutrition as part of their drug therapy.

Understanding Resistance to Anti-Infective Drugs

• Resistance refers to microorganisms' ability to adapt over time and become unaffected by specific anti-infective drugs, necessitating careful management.

• Microorganisms may develop resistance through various mechanisms such as producing enzymes that deactivate drugs or altering cellular structures to prevent drug entry.

Mechanisms of Resistance Development

• Changes in cellular permeability and binding sites on membranes or ribosomes can lead to reduced effectiveness of antimicrobial agents.

• Genetic mutations among microorganisms contribute significantly to resistance, allowing resistant cells to dominate after sensitive ones are eliminated.

Strategies for Preventing Resistance

• Limiting the use of antimicrobial agents strictly for specific pathogens is essential; culture and sensitivity tests should guide treatment duration.

• High enough doses and prolonged usage are necessary to eradicate even slightly resistant microorganisms while maintaining therapeutic levels.

Combination Therapy and Prophylaxis

• Combination therapy allows smaller doses of each drug, reducing adverse effects while enhancing efficacy against multiple organisms.

• Prophylactic antibiotic therapy is used in high-risk situations (e.g., surgeries or known cardiac conditions), aiming to prevent infections before they occur.

Adverse Reactions from Anti-Infective Therapy

• All anti-infective agents carry a risk of adverse effects; common issues include toxicity affecting kidneys, gastrointestinal tract disturbances, nervous system reactions, hypersensitivity, and superinfections.