43. Principles of chemotherapy Flashcards
(15 cards)
What are Chemotherapeutic agents?
They are chemical substances used to treat diseases, particularly infections and cancer. They are designed to actively target and destroy or inhibit the growth of harmful cells or organisms
Chemotherapeutics are classified into 3 main groups: Antimicrobial, antineoplastic, and antiparasitic agents.
What are antimicrobial drugs?
Targeting microorganisms like bacteria, fungi and viruses using antibacterial, antiviral and antifungal drugs.
- Antibacterial drugs: Used to treat bacterial infections
- Antiviral drugs: Used to treat viral infections. These drugs often work by interfering with the viral replication cycle
- Antifungal drugs: used to treat fungal infections, which can be localized or systemic
What is Antineoplastic drugs
Also known as anticancer drugs. They are used to treat cancer and target rapidly dividing cells, and disrupt the growth and proliferation
What is Antiparasitic drugs?
Used to treat parasitic infections.
- Antiprotozoal drugs: Used to treat infections caused by protozoa, such as malaria, giardiasia and amoebiasis
- Endoparasiticidal drugs: Used to treat infections caused by parasites that live inside the body, such as worms
- Ectoparasiticidal drugs: Used to treat infections caused by parasites that live on the surface of the body, such as lice, mites and fleas
How can we describe the principles of chemotherapy and the properties of antibacterial agents used in chemotherapy?
1. The mechanism by which chemotherapeutic agents work:
bactericidal vs bacteriostatic, mode of action
2. How they are classified and factors that affect the efficacy:
Selective toxicity, resistance, and post-antibiotic effect
What is bactericidal?
Refers to chemotherapeutic agents that directly kill the bacteria. Their action is reversible, leading to bacterial cell death
Example of bactericidal drugs
- Cephalosporins
- Aminoglycosides
- Metronidazole
- Potentiated sulphonamides
- Polypeptides
- Penicilins
What is bacteriostatic drugs?
These agents do not kill the bacteria but prevent them from growing, giving the host’s immunity system a chance to eliminate the infection.
give examples of bacteriostatic drugs
- Tetracycline
- Macrolides
- Lincosamides
- Pleuromutilins
- Phenicols
What is mode of action?
Antibiotics can be categorized based on how they kill or inhibit bacterial growth. Two main categories:
- Bactericidal vs bacteriostatic
- Concentration-dependent vs time-dependent
What is concentration-dependent drug?
Higher drug concentration = higher rate of bacterial killing.
the effectiveness is primarily dependent on a high peak concentration relative to the minimum inhibitory concentration of the target pathogen.
What is time-dependent drug?
To be effective, the antibiotics need to maintain sufficient concentration
What is Selective toxicity?
It refers to the ability of a drug to cause harm to a target organism without significantly harming the host organism (animal being treated).
This concept was founded by Paul Ehrlich. He envisioned drugs as “magic bullets” that could selectively target and destroy pathogens without damaging healthy tissues. This idea drove the development of many chemotherapeutic agents, such as salvarsan, ⭢ used to treat syphilis.
The therapeutic index measures the safety of the drug. It is the ratio between the dose that is toxic to the host and the dose that is effective against the target.
- High therapeutic index = indicates that the drug is safe. There is a large difference between the effective dose and the toxic dose.
- Low therapeutic index = indicates that the drug is relatively toxic. The effective dose is close to the toxic dose, and requires careful monitoring to avoid adverse effects
Drugs exert their effects by interacting with specific targets in the organism, which can be:
1. Unique target
Structures or processes that are specific to the target and not found in the host. They tend to have high toxicity
- Similar target
Structures or processes that are similar, but not identical, in the target and the host.
They have some degree of selective toxicity, but may also cause some side effects - Common target
structures or processes that are specific to the target and not found in the host.
They are generally toxic to both and have a low selective toxicity
What is resistance?
Bacteria can develop resistance to chemotherapeutic agents through various mechanisms, such as mutations, enzymatic inactivation of the drug or changes in cell permeability.
Resistance is a major challenge in chemotherapy.
What is Post antibiotic effect (PAE)?
A delayed antibacterial effect after the concentration of the drug has decreased below the minimum inhibitory concentration
