Antibacterials Flashcards
Drugs that inhibit cell wall synthesis
penicillins, vanomycin, carbapenems and cephalosporin
Drugs that affect protein synthesis
macrolides, tetracycline, and aminoglycosides
Drugs that affect transcription mechanisms
FQs
Drugs that affect metabolic pathways
sulfamethoxazole and trimethoprim
is sulfamethoxazole bactericidal or bacteriostatic
bacteriostatic because is is an antimetabolite
sulfamethoxazole is always sombined with
trimethoprim
Mechanism of sulfamethoxazole
prevents synthesis of folic acid
major use of sulfamethoxale
UTIs and otitis media
Do not use sulfamethoxazole in?
pregnant women, breastfeeding women or infants under 2 months of age
Rare side effect of sulfamethoxazole?
stevens johnson syndrome
Are beta lactam antibiotics bacteriostatic or bacteriocidal?
bacteriocidal because they cause lysis and death
3 groups of beta lactam antibiotics?
penicillins, cephalosporins and carbapenems
beta lactam antibiotics interfere with
cell wall synthesis
oral penicillin?
penicillin V
IV penicillin?
penicillin G
penicillins are active against?
most gram positive and some gram negative
what type of cell wall is more difficult to treat with antibiotics?
gram negative because it has 3 layers. the outer membrane is difficult to penetrate.
beta lactamase
enzyme produced by bacteria that destroys the beta lactam ring which is critical for drug activity
use penicillins with _______ to prevent penicillinase
clavulanic acid
Most common adverse effect with penicillins
allergy
cephalosporins and pharmacologically and structurally related to
penicillins
are cephalosporins bactericidal or bacteriostatic?
bactericidal because they cause lysis of the bacteria
as there is progression from 1st generation cephalosporins to 5th generation there is?
- increased activity towards gram negative
2. better ability to resist destruction by beta lactamases
Best generation of cephalosporins for gram positive coverage
first generation
first generation cephalosporins are used for?
surgical prophylaxis, URIs and otitis media
first generation cephalosporins have?
excellent gram positive coverage
Second generation cephalosporins do not?
kill anerobes
second generation cephalosporins have?
good gram positive coverage and better gram negative coverage then 1st generation
What is the most potent cephalosporin group for gram negative bacteria?
third generation
third generation cephalosporins can?
easily pass the meninges and diffuse into CSF for treatment of meningitis
Which generation of cephalosporins have the greates spectrum for gram positive?
fourth generation
fifth generation cephalosporins are used for?
MRSA infections
Patients with mild allergies to penicillin can?
take cephalosporins but with caution
adverse effects of cephalosporin
GI upset (most common), bleeding, thrombophlebitis and hemolytic anemia
Carbapenem prototype?
Imipenem
Drug group that are all parenterally given?
Carbapenems (imipenem)
Drug that is reserved for difficult to treat infections and only used in hospital?
Imipenem (a carbapenem)
Drug group that is effective against gram positive, gram negative and anerobes?
Carbapenems (imipenem)
Drug that has a resistance to Beta Lactamases
Carbapenems (imipenem)
Is imipenem bacteriastatic or bacteriocidal?
bacteriocidal. It weakens the cell wall causing lysis and death
Drug that inhibits cell wall synthesis but does not contain a beta lactam ring?
vanomycin
Drug used only in hospital to reduce chance of resistance?
Vanomycin
uses of vanomycin?
IV for MRSA and PO for C.Diff
Major adverse effect of vanomycin?
Infusion related reactions – vanomycin must be infused slowly
Rapid infusion of vanomycin causes
Red Man (redneck) syndrome
Vanomycin must be infused for
60 mins or more
Imipenem is used with ______ to inhibit breakdown in the kidneys
cilastatin
Principa toxicity of vanomycin
nephrotoxicity
Prototype of macrolides
erythromycin
is erythromycin (a macrolide) bacteriostatic or bactericidal?
Bacteriostatic but could be bacteriocidal depending on concentration and bacterial susceptibility
Mechanism of erythromycin
binds to 50s subunit and blocks addition of new amino acids to the growing polypeptide chain
Tetracyclines are
broad spectrum antibiotics
are tetracyclines bacteriostatic or bactericidal
bacteriostatic.
Mechanism of tetracyclines
inhibit protein synthesis by binding to 30s subunit. Addition of new amino acids to polypeptide chain is prevented.
Major adverse effects of tetracycline?
- Binds to metal ions and forms insoluble complexes (chelation) that cannot be absorbed
- Strong affinity for calcium so will cause discolouration of teeth when theyre being formed
the metal ions that form insoluble complexes with tetracycline are found in?
milk products, supplements, some laxitives and most antacids
When taking tetracycline with metal ions..?
administer tetracycline 1 hour before or 2 hours after
contraindications of tetracycline
do not use in children under 8 or in pregnant/breastfeeding women
GI disturbances of tetracycline
superinfection, diarrhea and C.Diff
tetracycline is antagonistic to?
bacteriocidal antibiotics so they must be taken at least an hour apart
prototype of aminoglycosides
gentamicin
aminoglycosides (gentamicin) have a?
narrow spectrum
Mechanism of gentamicin (aminoglycosides)
binds to 30s subunit to inhibit protein synthesis. Death results from insertion of abnormal proteins that cause lysis.
Is gentamicin bactericidal and bacteriostatic?
Bactericidal, it is the only protein synthesis inhibitor that is lethal
All aminoglycosides carry a positive charge meaning?
they must all be parenterally given because drugs with a charge cannot cross membranes
Gentamicin (aminoglycoside) is used for?
treatment of serious infections due to aerobic gram negative bacilii
Gentamicin is commonly used with _____ for a synergistic efffect?
vanomycin
Major Adverse effects of gentamicin (aminoglycoside)
nephrotoxicity and ototoxicity
Nephrotoxicity is?
reversible because cells are regenerated
ototoxicity is?
irreversible because cells are not replaced
How does Gentamicin produce ototoxicity and nephrotoxicity?
it binds tightly to renal tissue and readily penetrates the endolymph and perilymph
Dosage changes of gentamicin for people with kidney disease?
reduce dose or increase dosing interval
Ototoxicty with gentamicin can be made worse by?
loop diuretics
risk of ototoxicity with gentamicin is associated with?
increased lowest levels between doses, not the peak level and prolonged exposure
There is an increased risk of nephrotoxity when gentamicin is combined with?
- vanomycin
- cyclosporine (immunosuppresant)
- amphotericin B (antifungal)
prototype of FQs
ciprofloxacin
ciprofloxacin (an FQ) is used most commonly for
UTIs
Is ciprofloxacin (an FQ) bactericidal or bacteristatic?
bacteriocidal.
Mechanism of ciprofloxacin (an FQ)
inhibits enzymes needed for DNA replication and cell division. Alters DNA and prevents supercoiling.
Ciprofloxacin (an FQ) indications
major gram negative use and some gram positive