General principles of treatment and selection of antimicrobial regimens Flashcards
What proportion of population are on ABs?
1 in 3 hospital patients at any time
1 in 3 individuals will take at least one course durign a year
Basic principles of antibiotic use
- Administer an antibiotic that provides a level sufficient to inhibit or kill the infecting organism
- Continue treatment at least until the host is able to complete the curing and healing process
•Drain infections of closed spaces if necessary
(control the source of infection). Infections of avcesses do nut have bloodsupply, require surgicalsource control
Princicples of rational anitmicrobial use
Ensure effective treatment of patients with infections
Minimise ‘collateral damage’ from antimicrobial use
- Increased selection of resistant organisms
- Antibiotic treatment related illnesses eg Clostridium difficile infection. Niches become available when commencal microbialare wiped by broad spectrum ABs
- Increased risk of adverse effects
- Increased expenditure
questions to consider when assessing need for ABs
Does the patient have an infection?
- What is the likely source? (CLINICAL DIAGNOSIS)
- What are the likely causative microorganisms (MICROBIOLOGICAL DIAGNOSIS- need SAMPLES
Is an antibiotic needed or is the infection self-limiting?
Does the patient need urgent treatment or is there time to make a diagnosis?
Infection vs colonization in prescribing ABs
•Do not start antibiotics in the absence of
clinical evidence of bacterial infection
•Positive cultures from non-sterile sites eg wounds and catheter urines do not necessarily warrant treatment
Life-threatening infections requiring immediate treatment
- Unstable/deteriorating or severely septic patient (HIGH RISK OF DEATH RED SEPSIS)
- Neutropenic sepsis
- Meningitis
- Meningococcal sepsis
- Encephalitis
- Epiglottitis
- Necrotising fasciitis
- Toxic shock syndrome
High risk RED sepsis criteria
Determining which drug to use in suspected infection
Microbiological diagnosis
- Organism defined AND antibiotic susceptibility predictable or laboratory confirmed
Clinical diagnosis
- Empirical or ‘best guess’ therapy
- site directed eg. otitis media, pneumonia, UTI, meningitis
Implications for antibiotic selection
narrow spectrum = targeted
broad spectrum = where microbiology uncertain or infection caused by a mixture of organisms
Considerations in determining whether drug is safe for an individual
Known hypersensitivity or intolerance
Impaired excretion
- renal failure, liver failure
Drug interactions
- e.g. ciprofoxacin & theophylline
Higher risk of toxic effects
- bone marrow toxicity effects in transplant patients
- pre-existing liver disease
- CNS toxicity in epilepsy
Effect of Ca2+ antacids/Fe2+ on tetracycline
impair uptake
Dosing quinolones and penicillins
Cmax/MIC quinolones (eg ciprofloxacin)
Time > MIC penicillins (eg benzylpenicillin)
Deciding between cidal or static ABs
Cidal (eg penicillins, ciprofloxacin, gentamicin)
Static (eg tetracyclines, sulphonamide)
Situations when cidal agents preferred
Immunocompromised
- seriously ill
- steroid therapy
Immunodeficient
- neutropenia
- HIV
Difficult sites
- endocarditis
- meningitis
Advantages of switching from IV to oral ABs
Reductions in hospital-acquired bacteraemias and infected/phlebitic lines
Saves medical and nursing time
Reduces discomfort for patients and enables improved mobility and earlier discharge
Reduced treatment costs
Patient more likely to receive antibiotic at correct time
Potential to reduce risk of adverse effects
Criteria for switch from IV to oral
COMS
Clinical improvement observed
Oral route is not compromised
Markers are showing a trend towards normalising
Specific indication/deep seated infection
How long to treat:
- UTI (cystitis)
- Streptococcal pharyngitis
- Pulmonary tuberculosis
- Endocarditis
UTI (cystitis) – 3 days
Streptococcal pharyngitis – 10 days
Pulmonary tuberculosis – 6 months
Endocarditis – 4-6 weeks
•Most infections respond to 5 – 7 (10) days treatment according to severity of condition
