Antibiotics Flashcards
What are the 4 mechanisms of action of antibiotics?
Distruption of cell wall, inhibition of nucleic acid synthesis, inibition of protein synthesis and anti-metabolite activity
Give an example of some macrolide antibiotics?
Erythromycin, Clarithromycin and azithromycin
What is the mode of action of macrolides?
Bind to 50S ribosome subunit and inhibit protein synthesis
What bacteria are macrolides effective against?
gram +ve e.g. staphylococci spp. streptococci
gram -ve e.g H.influenzae, N.meningitidis
When is erythromycin used instead of Penicillin?
In a penicillin V allergy
Which of the three macrolides: erythromycin, azithromycin and and clarithromycin shouldn’t be taken with food?
erithroymycin and azithromycin
What drugs to macrolides inhibit the hepatic metabolism of?
theophylline, warfarin and statins
Give an example of some aminoglycoside antibiotics
gentamicin, tobramycin, amikacin
What is the mode of action of aminglycosides?
Enter bacterial cells via oxygen dependant system and bind to 30S subunit to inhibit protein synthesis
What bacteria are aminoglycosides effective against?
aerobes only and good against gram -ve esp. pseudomonas
Why must aminoglycoside use be monitored?
Causes ototoxicity and nephrotoxicity, has a narrow therapeutic range and has to be given IV
Name some quinolones
Ciprofloxacin, ofloxacin, levofloxacin
What is the mode of action of quinolones?
Inhibit DNA coiling by inhibiting DNA gyrase - bacteriocidal
What are the uses of quinolones?
only oral anti-pseudomonal abx
Active against gram -ve/+ve and anaerobes
What condition do you have to be careful when giving quinolones?
epilepsy, it reduces seizure threshold
Name some tetracyclines
Doxycycline, tetracycline, minocycline
What is the mode of action of tetracyclines?
Bind to ribosome to inhibit protein synthesis
What organisms are susceptible to tetracyclines and what are their common uses?
staphylococci, steptoccoi and gram -ve organisms - second line for skin/soft tissue infections
1st line for CAP
What are some adverse events with tetracyclines?
gastric irritation, discolouration and temporary growth stunting (pregnancy and children) and phototoxicity
What is the mode of action of Trimethoprim?
antimetabolite - inhibits bacterial conversion of folate to active form
Why is trimethoprim effective in UTI?
as it is excreted unchanged so there will be high concentrations in the urinary tract
What is the mode of action of metronidazole?
DNA damage in bacterial cells
What are the uses of metronidiazole?
anaerobic infections e.g BV, abscesses, aspiration pneumonia and giardia
What are some adverse effects of metronidiazole?
Rashes, metallic taste and extreme reaction when taken with alcohol
Name some glycopeptides
Vancomycin, teicoplanin
What is the mode of action of glycopeptides?
Inhibits cell wall synthesis - bacteriocidal
What are the uses of glycopeptides?
active against gram +ve organisms that are resistant to Beta lactam including MRSA
oral vancomycin for C.diff colitis
What are some concerns with using glycopeptides?
Red-man syndrome with vancomycin, nephrotoxicity and ototoxicity
What is the mode of action of rifampicin?
Inhibits DNA dependant RNA polymerase in bacterial cells
What is rifampicin effective against?
mycobacteria - TB and also staphylocci - always used with second abx though
How is rifampicin mainly excreted and what can happen?
Mainly in bile, urine and tears which may turn orange
What is the mode of action of Penicillins?
Interfere with cross-linking of bacterial cell wall in rapidly dividing cells
What are some examples of penicillins?
Penicillin V, Benzylpenicilin, flucloxacillin, amoxicillin
What organisms are not susceptible to penicillins and why?
Mycoplasma as they do not have a cell wall
What are some beta lactamase inhibitors that are conjugated with penicillins to make them effective in bacterial resistance?
clavulanic acid and tazobactam
What is the mode of action of cephalosporins?
Same as penicillin - interfere with cell wall cross linking in rapidly dividing cells
What are 1st generation cephalosporins used for?
skin and soft tissue infections
what are 2nd and 3rd generation cephalosporins used for?
gram -ve infections
Give some examples of cephalosporins?
cefalexin (1st gen), cefuroxime (2nd) and cefotaxime (3rd gen)
Phototoxicity reactions are common - patient needs to avoid direct sunlight and use high SPF suncreams if on this Abx
Doxycycline
A carbapenem administered IV once a day
Ertapenem
A penicillin not orally active. IV preparation used for treatment of meningitis and cellulitis
Benzylpenicillin
An antimetabolite used as first line treatment for UTI
trimethoprim
Use in patients with penicillin allergy as its spectrum of activity is similar. Withold statin during treatment with this drug
Clarithromycin
Brand name piperacillin and tazibactam. Used as first line teratment for HAP
tazocin
Active orally and IV against MRSA. Weekly FBC monitoring is essential during treatment
Linezolid
A carbapenem with extended spectrum of activity against pseudomonas infection
Meropenem
Use this antibiotic with caution in epilepsy as it can reduce seizure threshold
Ciprofloxacin
An oral 1st generation cephalosporn used for treatment of UTI
cefalexin
A penicillin predominantly active against staphylococcus. First line treatment for cellulitis
flucloxacillin
A glycopeptide that causes red-man syndrome if administerd too quickly
Vancomycin
Active against anaerobic bacteria. Patients should avoid alcohol
Metronidiazole
An aminoglycoside that inhibits protein synthesis. Serum drug level monitoring is required to detect accumulation
Gentamicin
This class of antibiotic should not be used in children under 12 years old as it deposits in bone and teeth
Tetracyclines
A beta lactamase inhibitor, used in combination with amoxicillin in co-amoxiclav to extend its spectrum of activity
Clavulanic acid
