Antibiotics Part 2 Flashcards
Name aminoglycosides
Gentamicin
Amikacin
How do we give aminoglycosides
IV as they are highly polarised
Indications for aminoglycosides
1) Severe sepsis
2) Pyelonephritis and complicated UTI
3) Biliary and intra-abdominal sepsis
4) Endocarditis
What do aminoglycosides lack action against
Strep. and anaerobces
Hence combine them with penicillin and/or metronidazole when the organism is unkown
Action of aminoglycosides
Bind irreversibly to bacterial 30S ribosomes and inhibit protein synthesis
THey are bacteriocidial
Range of action of aminoglycosides
Epctrum includes gram -ve aerboic bacteria
Staphylococci
Mycobacteria
How do aminoglycosides enter bacteria
Via an oxygen dependent transport system
This is absent in strep and anaerobes hence they have innate resistance
ADVERSE Effects of Aminoglycosides
Nephrotxicity - potentailly reversibly
Ototoxicity –> may be ireversible
They accumulate in renal tubular epithelial and cochlear and vestibult hair cells –> here they trigger apoptosis and cell death
How does nephrotoxicitiy with aminoglycosides present
Reduced urine output
Increased urea and creatinine
How does ototoxcitiy with aminoglycosides present
Often not notived until after resolution of acute infection
May complain of hearing loss, tinnitus (cocheal damage) and vertigo (vestibular damage)
Warnigns of using aminoglycosides
Caregul monitoring or plasma conc. in neonates, elderly and renal impairment
Contraindications of aminoglycosides
Myasthenia gravis –> c an impair neuromuscular transmission
Interactions of aminoglycosides
1) Loop diuretics or vancomycin –> increased risk of ototoxictiy
2) Ciclosporin, platinum chemotherapy, cephalosporins, vancomycin –> increased risk of nephrotoxicity
Name cepaholosprins
Cefalexin
Cefotaxime
Name carbapenems
Meropenem
Ertapenem
Indicatiosn for cepaholosporins and carbapenens
1) 2nd and 3rd line treatment for urinary and respiratory tract infections –> oral cephalosporins
2) Very severe/complicated infections caused by antibitoics resitant organisms –> reserve IV ccephalosporins and carbapenems for this
Actions of cepaholosporins and carbapenems
Inhibit enzyme responsible for cross linking peptidoglycans in bacterial cell walls –> cant maintain an osmotic gradient –> bacterial cell swilling –> lysis and death
Both have a broad spectrum of activity
Why are cepaholosporins and carbapenems more resistant to beta lactamases then penicillines
As the fusion of a beta lactam ring with a dihydrothiazine ring (cephalosporins and a unique hydroethyl side chain in carbapenems
Adverse effects of cepaholosporins and carbapenems
1) GI upset
2) Hypersesntivity
3) CNS toxicity –> including seizures. Particularly with high dose carbapenems in those with renal impairment
Warnings of using cepaholosporins and carbapenems
Risk of C. DIff
Caution of carabapenems and epilepsy
Interactinos of cepaholosporins and carbapenems
Can enhance warfarin effect
Cephalosporins increase the nephrotoxicty of aminoglycosides
Carbapenems decrease the plasma conc. and efficacy of valproate
Name the pencillin with anti-pseudomonal action
Piperacillin with tazobactam aka Tazocin
Indication of anti-pseudomonal penicillin
Severe infections - particularlly when there is a broad spectrum of potential pathogens
Antibitoic resistance is likely (i.e. hospital acquired infetions)
Immunocompromised patients
Specific clinical infections treated with tazocin
1) LRTI
2) Intra-abdominal sepsis
3) UTI
4) Skin and soft tissue infections
Why does tazocin have activity against pseudomonas
As in piperacillin the side chain has been converted to a form of urea
This increases activity to include pseudomonas
Tazocin is a beta-lactamase inhibitor –> therefore has activity against beta-lasctamase producing bacteria e.g. S. Aureus and gram-ve anaerobes
Adverse effects of anti-pseudomonal penicllines
1) GI Upset
2) antibiotic associated colitis
3) Hypersensitivity
Warning of using tazocin
1) Caution if risk of C. DIff infection
2) Reduce dose in moderate/severe pencillin allergy
Interactions of tazocin
1) Methotrexate - reduces renal excretion hence increased risk of toxicity
2) enhances warfarin
can you get tazocin in the community
No 0 it is hospital only
Each dose of tazocin contains about 10mmol of Na and is infused in 50-150mls of fluid
Remember to take this into account when determining the need for supplementary fluid, particularly in heart failure.
Name broad-spectrum penicllines
Amoxicillin
Co-amoxiclav (amoxicllin and clavulinac acid)
Indications for the use of broad-spectrum antibiotics
1) empirical pneumonia treatment - due to gram +ve (S. pneumonia) or gram -ve (H. Influenzae)
2) Empirical UTI treatment (most commonly due to E. Coli)
3) Part of combo treatment for intra-abdominal sepsis or hospital acquired infections
4) Part of treatment for H. Pylori associated ulcers
Action of broad-spectrum antibitoics
Inhibits enzymes that cross-link peptidoglycan in bacterial cell walls - weakened walls cant maintain osmontic gradient –> uncontroled water entry –> lysis and death
Why does amoxicllin hace increased activity against gram-ve bacteria
As in amoxicillin the addition of an amino group o the beta-lactam ring increases their activity against gram-ve bacteria
Hence this makes them more broad spectrum
What is co-amoxiclav
Amoxicillin and clavulanic acid
What is the action of clavulanic acid in co-amoxiclav
It is a beta-lactamse inhibitor
THis increases the spectrum of cover further to include beta-lactamse producing bacteria (S. aureus and gram-ve anaerobes)
Adverse effects of broad spectrum penicillins
1) GI Upset
2) Antibiotic associated collitis
3) Allergy
Warnings of broad spectrum penicillin
1) caution if risk of C. diff e.g. hospital or elderly
2) Lower dose in severe renal impairment –> risk of crystaluria
Interactions of broad spectrum penicillin
1) Methotrexate - reduces renal exretion, hence increasd risk of toxicity
2) Enhance warfarin
Name penicillinase resistant penicillins
Flucloaxcillin
Indications of flucloxacillin
STAPHYLOCOCCAL INFECTIONS e.g.
1) Skin and soft tissue
2) Osteomyeltis and septic arthritis
3) Endardatiis
How does flucloxacillin have activity against beta-lactamase producing bacteria
It has an axyl side chain on the beta-lactam ring
This protects the ring from beta-lactamases
How does MRSA resist flucloaxcilllin
It reduces the penicillin binding affinity
Adverse effects of flucloxacillin
1) GI Upset
2) Allergy
3) Liver toxicity –> including cholestasis and hepatitis
4) CNS toxicity - in high doses or severe renal impairment
Warninngs of flucloxacillin
1) Renal failure - may require dose reduction
Interactions of flucloaxcillin
2) Methotrexate - redudces its renal excretion hence increased risk of toxicity
How long should you give flucloxacillin for deep seated infections
6 weeks e.g. endocarditis and osteomyelitis
It has a short plasma half life and is rapidly renallyexcreted hence give every 6 hours
Name standard penicllins
Benzylpenicillin
Phenoxymethylpenicillin (penV)
Indications for pencillin
1) Streptococcal infection - includes tonsilitis, pneumonia (with macrolide if severe), endocarditis, skin & soft tissue infections (with flucloxacillin if severe)
2) Clostridial Infections e.g. tetanus
3) Meningococcal infections e.g. meningitis and septicaemia
actions of penicillins
Inhibits the enzymes responsible for cross-linking peptidoglycans in bacterial cell walls
How do bacteria acquire resistance to pencillins
Bacteria make beta-lactamase enzymes
This breaks the beta-lactam ring
How common are pencillin allergy
affects 1-10% of people
Usually skin rash 7-10 days after first exposure or 1-2 days after repeat
Less commonly is an anaphylactoid reaction - hypotension, bronchial spasm, angioedema
Adverse effects of pencillins
1) allergy
2) CNS Toxicity –> including convulsions and coma
Warnings of using penicillins
1) Renal Impairment
Interactions of penicillins
1) methotrexate - reduces its renal excretion hence increased risk of toxicity
How can you give benzypenicillinsn
IV or IM as hydrolysis by gastric acid prevents GI absorption
How can you give PenV
It is stable in gastric acid hence can be given orally
What would you prescrive for young person with a sore throat
If it requires antibitoics GIVE PENV (not amoxicillin)
This is because if the sore throat due to EBV amoxicillin it causes rash - mistaken for allergy
