Chemotherapy of Infection Flashcards
(61 cards)
What synthetic chemicals be used to destroy infective agents?
Trypan Red (Trypanosomiasis) Atoxyl (Trypanosomiasis) Salvarsan (Syphilis)
What must chemotherapy drugs be?
Selective
i.e. drug must kill the pathogen and not the host
What was the chemotherpeutic index defined as by Paul Ehrlich?
“minimum curative dose as a fraction of the maximum dose tolerated by patient”
What is an example of calculating therapeutic index?
Salvarsan will cure syphilis at a dose of 5mg/kg/day
A dose of 15 mg/kg/day may have severe-to-fatal toxic effects on the patient
The therapeutic index is 3
What is chemotherapy?
Use of chemicals, either natural or synthetic to
Kill or inhibit growth of infectious agents
Inhibit the growth of malignant cells
:
What are chemotherpeutic agents?
Are intended to be toxic to pathogens or cancer cells
But harmless to the host or normal cell
What is selective toxicity?
Acceptable toxicity vs benefit
All toxicity is a matter of dosage
What must chemotherapeutic agents be able to do?
Exploit difference between the host and the invading micro-organism
Or between normal cell and cancer cell
Why is difficult to achieve selectivity toxicity in cancer chemotherapy?
Cancer cells are too similar to normal host cells
In cancer side effects are more readily accepted
What are Protozoa and Helminths?
Eukaryotes
What is chemotherapy used to treat infection with?
Bacteria Viruses Fungi Protozoa Helminths Ectoparasites
What makes a drug selective?
Unique target in pathogen
Different importance of target
Different stability of target protein
Drug has higher affinity for pathogen and host enyme
How does a unique target in pathogen make a drug selective?
Identified through comparative genomics
E.g. haemoglobin degradation by Plasmodium (in eukaryote)
How does different importance of target make a drug selective?
Target present in host and in pathogen
Essential only in pathogen
How does different stability of target protein make a drug selective?
Target present and essential in host and pathogen
Target enzyme quickly replaced by host
How does a drug having a higher affinity for pathogen and host enzyme make a drug selective?
Low drug concentrations inhibit pathogen enzymes first
What is penicillin?
A naturally occuring substance produced by a micro-organism that killed other microorganisms
What is an antibiotic?
Antibiotics are specific chemical substances produced by living organisms for chemically derived from those substances that are capable of inhibiting the life processes of other organisms (kill or inhibiting growth)
Why do organisms produce antibiotics?
To defend themselves from micro-organisms such as (other) bacteria, parasites, fungi
What do some antibiotics have activity against?
Eukaryotes, parasites and fungi
What do antibiotics not work against?
Viruses
Are synthetic antibacterials such as sulphanoamide drugs or bleach antibiotics?
No
What are limitations of antibiotics?
Ineffective against viruses Ineffective against most protozoan parasites and helminths Difficult to synthesise/derivatise Can be expensive Antibiotic resistance Cannot optimise their properties
What are the key differences between bacterial and mammalian cells?
Bacterial cels require para-amino nezoic acid (PABA)- mammalian cells do not (need to get in diet, eat green vegetables)
Bacterial cells have cell walls- mammalian cells do not
Bacterial cell ribosomes have 30S and 50S sub-units- mammalian cells have 40S and 60S ribosomal sub-units
