Antibiotic Classes Flashcards
Name 1 e.g. of a tetracycline antibiotic and 2 indications for their use
-Doxycycline, lymecycline
Indications for use of doxycycline, name 2:
- acne (inflamed pustules/papules/cysts)
- lower RT infections e.g. infective exacerbations of COPD (H.influenzae, pneumonia, and atypical pneumonia (mycoplasma, chlamydia psittaci, coxiella burnetti)
- chlamydial infection inc. pelvic inflamm disease
- other infections e.g. typhoid, anthrax, malaria, lyme disease..
Tetracyclins have quite a ____-spectrum of activity against ___ and ___ organisms.
Their use is limited by increasing ____ ___
- broad spec vs gram + and gram - organisms
- limited by bacterial resistance
Tetracyclins MOA
- they inhibit bacterial _____ ____.
- they bind to the 30S _____ subunit found in bacteria, which prevents binding of ____ to ___
- this prevents the _____ of new ___ ___ to growing ____ ___ chains
- this is _____ (stops bacterial growth) so assists immune system in killing and removing bacteria
- what is the main MOA of resistance to this class which has developed?
- inhibit protein synthesis
- bind to ribosomal subunit, prevents tRNA binding to mRNA
- prevents the addition of new amino acids to the growing polypeptide chains
- this is bacteriostatic
- efflux pump (allows bacteria to pump out tetracyclines-preventing cytoplasmic accumulation)
Name 4 SEs of tetracycline use
- nausea
- vomiting
- diarrhoea
- hypersensitivity reactions (1%)
- oesophageal irritation, ulceration and dysphagia
- photosensitivity (sunburn reaction when skin exposed to light)
- discolouration +/- hypoplasia of tooth enamel in children
- hepatotoxicity, intracranial hypertension are rare
Tetracyclines bind to divalent cations, therefore should not be given within 2hrs of
-___
-___
or __
as this would prevent antibiotic absorption
- calcium
- antacids
- iron
How can tetracyclines enhance Warfarin’s anticoag. effect?
-they kill normal gut bacteria that synthesis vitamin K so there is less vitamin K concentration and Warfarin’s action is more potent as a result,
In acne rx, an 8week course of doxycyline is give, what is the length of dose for infective COPD exacerbation?
-5-7days
Metronidazole works against what bacteria/protozoa?
-anaerobic
Metronidazole is reduced in anaerobic bacteria which generates a nitroso free radical that binds to DNA -> degradation and death. Suggest 2 indications for it’s use.
- antibiotic associated collitis (caused by gram+ anaerobe c.diff)
- oral infection/abscess or aspiration pneumonia (caused by gram - anaerobes in mouth)
- surgical and gynae infections caused by anaerobes from colon
- protozoal infections e.g. TV, amoebic dysentery and giardiasis
Due to it’s metabolism, people with severe disease of what organ should not be prescribed metronidazole?
- liver
- CYP450 metabolised
It is contraindicated to have what alongside the abx Metronidazole due to SEs of: flushing, headache, N&V (_____-like reaction)
- CI: ALCOHOL
- (disulfiram-like reaction)
Interactions:
Metronidazole increases the risk of toxicity of what medication?
-Lithium
Vancomycin indications, there are 2:
- rx gram + infection if severe or resistant/allergic to penicillins
- rx of antibiotic associated colitis caused by C. diff (2nd line after Met)
Vancomycin has a narrow spectrum vs gram + bacteria, suggest 2
- staphlococcus aureus (and MRSA)
- streptococcus
- C. difficile
Vancomycin inhibits growth and cross-linking of peptidoglycan chains so inhibits what?
-the synthesis of the cell wall of Gram + bacteria (hence lysing and killing the bacteria)
What is the most common adverse effect of vancomycin infusion?
Another adverse effect if infused too rapidly is “___ ___ syndrome” characterised by what?
- most common = thrombophlebitis at infusion site
- Red Man Syndrome = generalised erythema, +/- hypotension, bronchospasm
What 2 organs is Vancomycin toxic to? What effect can Vancomycin have on parameters you’d check in a full blood count?
- nephrotoxic (-> renal failure, interstitial nephritis)
- ototoxic (tinnitus, hearing loss)
- blood: neutropenia, thrombocytopenia
Amikacin (systemic) and neomycin (topical) belong to what class of antibiotics? NB: especially effective against gram negative aerobes
-Aminoglycosides (like gentamicin)
Aminoglycosides are useful against gram + aerobes e.g. P_____ _____
-suggest 3 indications for their use:
- Pseudomonas aeruginosa
- severe sepsis
- intra-abdo sepsis
- pyelonephritis
- endocarditis
- topical for bacterial skin, eye, ear infections
Aminoglycosides bind irreversibly to what in bacterial to inhibit protein synthesis?
-to bacterial ribosomes 30S subunit
Ototoxicity secondary to aminoglycosides is often a later, irreversible complication. However, nephrotoxicity can be noticed earlier and may be reversed. What would make you worried about nephrotoxity?-
- reduced urine output
- rising creatinine and urea
Aminoglycosides are renally excreted. Suggest 3 pt groups you need to be cautious about prescribing these in?
- neonates
- elderly patients
- those with renal impairment
- myasthenia gravis (they impair neuromuscular transmission)
Chloramphenicol is a broad spectrum antibiotic. Drops are used for ______ and otitis___.
- conjunctivitis
- otitis externa
Common adverse effect of chloramphenicol is what sx upon application of drops?
And what can happen if neonates are exposed (unable to metabolise and excrete –> what syndrome?)
- stinging, burning, itching on application
- Grey Baby Syndrome due to circulatory collapse
Penicillin e.g. Benzylpenicillin, phenoxymethylpenicillin
-give 2 indications and state it’s MOA
- rx for streptococcal infection e.g. tonsillitis, pneumonia, endocarditis..
- rx for meningococcal infection
- rx for clostridial infection e.g. gas gangrene
- inhibit enzymes responsible for crosslinking peptidoglycans in bacterial cell walls
What toxicity can occur with v high-dose penicillin therapy or accumulation due to renal impairment?
-Neurological toxicity
Flucloxacillin is a penicillinase-resistant penicillin, suggest 2 indications:
-it has a narrow spectrum of activity against gram … s____
- skin and soft tissue infections e.g. cellulitis
- osteomyelitis & septic arthritis
- endocarditis
- vs. gram + staphylococci
What rare but serious organ toxicity can occur with flucloxacillin therapy/up to 2 months after completion of treatment? Suggest how this may manifest?
-liver toxicity
-e.g. cholestasis, hepatitis
NB: prior fluclox-related hepatotoxicity is a CI to future use
Macrolides e.g. Clarithromycin, erythromycin, azithromycin are often used in place of penicillin if allergy is present. They are useful in what type of infection to cover what? And are used with a PPI and amox/metronidazole in treatment of what?
- in severe pneumonia added to penicillin to cover atypical organisms (e.g. legionella, mycoplasma)
- treatment to eradicate H. pylori
MOA of macrolides (suffix -___)
suffix = omycin
- they inhibit protein synthesis by binding to the 50S ribosome subunit
- here they block translocation so is bacteriostatic/stops growth
Macrolides e.g. erythromycin are irritants.
Given orally can cause –>
Given IV can cause –> ____
orally: nausea, vomiting, abdo pain, diarrhoea
IV: thrombophlebitis