Antibiotics Flashcards
What are the first line antibiotics in the management of a UTI?
- Nitrofurantoin
- Trimethoprim
- 3 day course in (non-pregnant) women
- 7 day course in men
- Pregnancy - nitrofurantoin 7 days is first line
What drug class is nitrofurantoin from?
- Nitrofuran
What is the mechanism of action of nitrofurantoin?
- Poorly understood
- Affects protein synthesis
- Activated by nitrofuran reductase within the cell
- Reactive metabolites inhibit bacterial enzyme synthesis
- Important proteins (DNA, RNA, cell wall protein) cannot be made
What allows nitrofurantoin to concentrate in the urine?
- Up to 50% of the PO dose is excreted in the urine in an unchanged form
What are the indications of nitrofurantoin?
- Treatment of lower UTI
- Prophylaxis of UTIs
What are the adverse effects of nitrofurantoin?
- Discolouration of urine
- Pulmonary fibrosis
- Hepatic disorders
- Peripheral neuropathy
- Anaemia/thrombocytopenia/agranulocytosis
What are the contraindications of nitrofurantoin?
- Avoid in renal impairment (renally excreted)
- Avoid in pregnancy at term (risk of neonatal haemolysis)
What are the indications of trimethoprim?
- Treatment of lower UTI
- Prophylaxis of UTI
- Treats other infections such as pyelonephritis/prostatitis/diverticulitis
What is the mechanism of action of trimethoprim?
- Folate antagonist
- Inhibits bacterial dihydrofolate reductase
- Bacterial nucleic acids (RNA, DNA) and proteins can’t be made
What are the adverse drug reactions of trimethoprim?
- Risk of teratogenicity in the first trimester
- Avoid in pregnancy
What is a major DDI of trimethoprim?
- Both folate antagonists
- Both inhibit dihydrofolate reductase
- Consequence is severe bone marrow suppression
What is the drug class of gentamicin?
- Aminoglycoside
What are the other drugs in the aminoglycoside drug class?
- Vancomycin
- Streptomycin
- Neomycin
- Tobramycin
What is the mechanism of action of gentamicin?
- Inhibit protein synthesis
- Binds to 30s subunit of bacterial ribosome
What are the indications of gentamicin?
- Septicaemia
- Otitis externa
- Meningitis
- Biliary tract infection
- Pneumonia
- Prostatitis
What are the adverse effects of gentamicin?
- Nephrotoxicity
- Ototoxicity (hearing loss/vertigo/tinnitus)
Why do we need to monitor aminoglycosides therapeutically?
- Monitor serum aminoglycoside concentration due to narrow therapeutic index
What else needs to be monitored when treating a patient with aminoglycosides?
- Check U&Es before and during treatment
- Also monitor auditory and vestibular function during treatment
When can aminoglycosides not be used?
- In renal impairment, clearance of gentamicin is reduced and toxicity can occur
What is the mechanism of action of amoxicillin?
- Inhibition of cell wall synthesis
- Binds to transpeptidase’s active site and blocks its activity
- Interrupts bacterial cross-linking and cell wall synthesis
Why is the addition of clavulanic beneficial for treating certain infections?
- It is a beta-lactamase inhibitor
- Overcomes resistance in beta-lactamase secreting bacteria
When should antibiotic prescriptions be reviewed?
- Following a senior review of the patient
- Following any change in clinical condition
- Daily, typically on ward round
- Following the receipt of relevant investigation/culture results
What factor is most important for determining when to change IV antibiotics to the enteral route?
- The overall clinical picture and patient improvement
Outline CURB-65
- Confusion = 1 point
- Urea >7 mmol/L = 1 point
- RR >30 = 1 point
- BP <90/60 mmHg = 1 point
- Age >65 = 1 point
What is the mechanism of action of clarithromycin?
- Inhibition of protein synthesis
What drug class is clarithromycin in?
- Macrolides
Which drug should be withheld when a patient is on erythromycin?
- Statins
Which antibiotic is used to treat paediatric meningococcal sepsis?
- Ceftriaxone
Which antibiotic class does ceftriaxone belong to?
- Beta lactams
- It is a cephalosporin
What is cephalosporin good for?
- Provides good broad spectrum cover against gram positive, gram negative and anaerobic organisms
What is the mechanism of action of acyclovir?
- Converted to acyclovir monophosphate
- Then to acyclovir triphosphate - a potent inhibitor of viral DNA polymerase
- Acyclovir monophosphate form incorporates into replicating DNA, causing chain termination
What are the indications for acyclovir?
- Herpes simplex virus (HSV 1 and HSV 2)
- Causes encephalitis, genital herpes and cold sores
- Varicella zoster virus
- Causes shingles, chickenpox
- Acyclovir also prevents infection in the immunocompromised and pregnancy
