CHEMOTHERAPEUTIC AGENTS AND MODE OF ACTIONS GAINST INFECTIOUS DISEASES

 Properties of chemotherapeutic agents:

 Spectrum of Activity:

• Broad-spectrum: Effective against a wide range of microorganisms.
• Narrow-spectrum: Effective against a limited number of microorganisms.

2. Mechanism of Action:

• Cell wall synthesis inhibition: Disrupting the formation of the microbial cell wall, leading to cell lysis.
• Protein synthesis inhibition: Interfering with the microbial protein production, halting growth.
• DNA/RNA synthesis inhibition: Blocking the replication or transcription of microbial genetic material.
• Metabolic pathway disruption: Interfering with essential metabolic processes in the microorganism.

3. Potency:

• Minimum Inhibitory Concentration (MIC): The lowest concentration of a chemotherapeutic agent that inhibits the growth of a microorganism.
• Minimum Bactericidal Concentration (MBC): The lowest concentration of a chemotherapeutic agent that kills the microorganism.

4. Pharmacokinetics:

• Absorption: How well the chemotherapeutic agent is absorbed into the body.
• Distribution: How the chemotherapeutic agent is distributed throughout the body.
• Metabolism: How the chemotherapeutic agent is broken down by the body.
• Excretion: How the chemotherapeutic agent is eliminated from the body.

5. Toxicity:

• Selective toxicity: The ability of a chemotherapeutic agent to target microorganisms without harming the host.
• Adverse effects: Unwanted side effects that may occur with the use of a chemotherapeutic agent.

6. Resistance:

• Development of resistance: Microorganisms can develop resistance to chemotherapeutic agents, making them less effective.
• Mechanisms of resistance: Microorganisms can develop various mechanisms to evade the effects of chemotherapeutic agents.

7. Stability:

• Chemical stability: How stable the chemotherapeutic agent is over time and under different conditions.
• Storage conditions: Proper storage conditions are essential to maintain the stability and effectiveness of chemotherapeutic agents.

Antibacterial mode of action:

Cell wall synthesis inhibition:

• Antibiotics in this class interfere with the synthesis of peptidoglycan, a crucial component of the bacterial cell wall.
• This weakens the cell wall, leading to bacterial lysis and death.

Protein synthesis inhibition:

• Antibiotics in this class target bacterial ribosomes, the protein-making machinery, without affecting human ribosomes.
• They disrupt different stages of protein synthesis, preventing bacteria from producing essential proteins.

DNA/RNA synthesis inhibition:

• Antibiotics in this class interfere with various processes involved in DNA/RNA synthesis.
• Some block the enzymes responsible for DNA replication or RNA transcription, while others damage the DNA itself.

Metabolic pathway disruption:

• Antibiotics in this class target specific enzymes involved in these pathways, disrupting essential metabolic processes.
• For example, sulfonamides interfere with folic acid synthesis, which is crucial for bacterial growth.

Cell membrane disruption:

• Antibiotics in this class disrupt the structure or function of the bacterial cell membrane.
• This leads to leakage of cellular contents and bacterial death.

Antifungal mode of action:

Cell wall synthesis inhibition:

• Antibiotics in this class interfere with the synthesis of peptidoglycan, a crucial component of the bacterial cell wall.
• This weakens the cell wall, leading to bacterial lysis and death.

Ergosterol synthesis inhibition:

• Antifungal drugs in this class interfere with the enzymes involved in ergosterol synthesis.
• This depletes ergosterol in the fungal cell membrane, leading to cell damage and death

Cell wall synthesis inhibition:

• Antifungal drugs in this class target the enzymes responsible for synthesizing these polysaccharides, such as glucan synthase.
• This weakens the fungal cell wall, making it more susceptible to damage and lysis.

Nucleic acid synthesis inhibition:

• Fungal cells need to replicate their DNA and transcribe it into RNA to grow and divide.
• Antifungal drugs in this class interfere with various processes involved in DNA/RNA synthesis in fungal cells.

Antiviral mode of action:

Attachment and entry inhibition:

• Viruses initiate infection by attaching to specific receptors on the surface of host cells.
• Antiviral drugs in this class block these receptors, preventing the virus from attaching and entering the cell.

Uncoating inhibition:

• Once inside the cell, the virus needs to shed its outer coat (uncoating) to release its genetic material.
• Antiviral drugs in this class interfere with this uncoating process, preventing the virus from replicating.

Nucleic acid synthesis inhibition:

• Antiviral drugs in this class target the enzymes responsible for viral nucleic acid synthesis, such as viral polymerases or reverse transcriptase.
• This prevents the virus from replicating its genetic material and halts further viral production.

Protein synthesis inhibition:

• Viruses need to produce viral proteins to assemble new viral particles.
• Antiviral drugs in this class interfere with the synthesis of specific viral proteins, preventing the virus from multiplying.

Assembly and release inhibition:

• After viral components are produced, they need to be assembled into new viral particles and released from the host cell to infect other cells.
• Antiviral drugs in this class interfere with the assembly or release of viral particles, preventing the spread of infection.

Antiprotozoal mode of action:

Interference with nucleic acid synthesis:

• Protozoa need to replicate their DNA and transcribe it into RNA to grow and divide.
• Antiprotozoal drugs in this class interfere with various processes involved in DNA/RNA synthesis in protozoan cells.

Disruption of metabolic pathways:

• Protozoa have unique metabolic pathways that are essential for their survival.
• Antiprotozoal drugs in this class target specific enzymes involved in these pathways, disrupting essential metabolic processes.

Interference with protein synthesis:

• Protozoa need to produce proteins to survive and multiply.
• Antiprotozoal drugs in this class target protozoan ribosomes, the protein-making machinery, without affecting human ribosomes.

Disruption of cell membrane function:

• The protozoan cell membrane acts as a barrier, regulating what enters and exits the cell.
• Antiprotozoal drugs in this class disrupt the structure or function of the protozoan cell membrane.

Inhibition of parasite-specific enzymes:

• Some antiprotozoal drugs target enzymes that are unique to protozoa and not found in humans.
• This allows for selective toxicity, killing the protozoa without harming the host.