antibacterial drugs Flashcards
When looking at the ideal antibiotics what factors do we consider
- Spectrum of action
- Effect on the patient’s cells
- Route of administration
- Duration of action
- Route of excretion/ metabolism
- Interaction with other drugs
- Side effects
- Resistance
What do we mean by effect on bacteria
bacterostatic vs bactericidal
What do we mean by bacterostatic
Antibiotic stops replication of bacteria
What do we mean by bactericidal
Antibiotics kills bacteria
Do we prefer bactericidal or bacterostatic effect on bacteria
bactericidal
What do we mean by spectrum of action
Narrow vs broad
What do we mean narrow spectrum of action
Antibiotic strops replication or kills a narrow range of bacterial species
What do we mean broad spectrum of action
Antibiotic strops replication or kills a wide range of bacterial species
Do we prefer a narrow or broad spectrum of action
It depends on if the broad spectrum will harm our healthy bacteria
Do we want the antibiotic to affect the patients cells
no
What can happen if antibiotics affect the patents cells
- Allergies
- Autotoxic
- Can damage the kidneys
- Can damage the lover
Do want the antibiotic to have a short or long duration of action
Long so need to take it at larger intervals
What actions can antibiotics inhibit to affect bacterias life
- DNA replication
- Ribosome funciton
- Folate synthesis
- Cell wall synthesis
Give examples of antibiotics that affect DNA replication
Metronidazole
Give examples of antibiotics that affect Ribosome function
Macrolides
Tetracycline
Aminoglycosides
Give examples of antibiotics that affect folate synthesis
Suphonamide
Trimethoprim
Give examples of antibiotics that affect cell wall synthesis
Penicillins
Cephalosporins
How does Metronidazole work
By inhibiting DNA replication and degrading existing DNA
List the qualities of Metronidazole
- Indicated against anaerobic infections
- Bacterocidal
- Interacts with alcohol
How does Metronidazole interact with alcohol
Prevents the metabolism of alcohol leading to severe nausea and vomiting
Name some macrolide antibiotics
- Erythromycin
- Clarithromycin
- Azithromycin
How do macrolide antibiotics work
They bind to 50s ribosome subunits
List the qualities of macrolides
- Bacteriostatic
- Broad spectrum
- Can cause Gastrointestinal disturbances
How does tetracycline work
Binds to 30s ribosome subunits thus inhibiting protein synthesis
List the qualities of tetracycline
- Mixed bactericidal and static
- Broad spectrum
- Is deposited in growing bones and teeth leading to staining
How do aminoglycosides work
inhibits 30s ribosome subunits thus inhibiting protein production
List the qualities of aminoglycosides
- Bactericidal
- Broad spectrum agaisnt gram negative bacteria
- Used often in combination with cephalosporin
- Nephrotoxic and ototoxic
How do trimethoprim work
Inhibits folate synthesis and interferes with DNA replication
List the qualities of trimethoprim
- Bacteriostatic
2. Frequently used in UTIs
How do penicillins and cephalosporins work
- Inhibit peptidoglycan cross linking in cell wall
List the qualities of penicillins
- Bactericidal
2. Narrow spectrum
List the qualities of cephalosporins
- Bactericidal
2. broad spectrum
List the qualities of amoxicillin
- Bactericidal
2. broad spectrum
What do we usually prescribe penicillins or cephalosporins with
Clavulanic acid or co amoxiclav to tackle resistance
How can bacteria become resistance
- Can precent entry of antibiotic into cell
- Cleavage of antibiotic structure eg beta lactamases
- Alteration to structure making antibiotic unable to enter or bind to cell
- Can alter site of action of the antibiotic
what are the general precision we take with antibiotics
- All antibiotics can interfere with gut flora
- Risk of clostridium difficile
- Interaction with warfarin
