micro lecture 19 Flashcards
how do adverse effects affect antimicrobials?
All antimicrobial agents may (will) produce
adverse effects. Most are of short duration
and minor. Some are serious and
potentially life threatening
Most common side effects are GI tract
related e.g. nausea, vomiting and
diarrhoea. Skin rashes also commonly
occur.
what are the three results from antimicrobial combination therapy?
Combinations of antimicrobial agents can produce three possible results: Synergism Additive Antagonism
Combinations are rarely used, except in what?
-Acute and potentially life threatening illnesses
usually when the causative organism (and sensitivity
profile) are unknown
- Infections where synergy is required
- Where the possibility of drug resistance may occur
what are the possible failures of antimicrobial chemotherapy?
Drug has little or no activity against infecting organism or strain (poor, or unlucky initial, selection)
Compliance or dosing error (intake too low)
Drug cannot reach the site of infection e.g. with intracellular pathogens (poor, or unlucky initial, selection)
Infection occurs in the presence of poor
vascularisation and possibly necrotic material
(poor delivery)
Infection occurs in the presence of pus
(poor penetration)
‘Foreign’ material is present e.g. catheters, hip
prostheses (mucoid colonisation – poor penetration)
what to consider with paediatric prescribing?
Newborn children are more prone to infections
requiring antimicrobial agents than adults
Renal function – very variable with age:
Creatinine clearance of a neonate is about 1/3 of
that of an older child. Difference is due to
maturation of glomerular and tubular functions
“Adult” glomerular filtration rate is achieved by
the age of 12 months – then gets even better
Volume of distribution: Extracellular fluid volume is proportionally larger
in neonates compared to older child (and adult)
Hepatic enzyme systems: Some enzyme systems are immature in the
neonate (e.g. glucuronidation of chloramphenicol
may be delayed. This can result in ‘grey baby’
syndrome – hypotension, cardiovascular collapse
and death)
Deposition in actively growing tissues:
Tetracyclines may be deposited in the bones and
teeth of children resulting in dental staining
Formulations are often liquids and usually heavily
flavoured to encourage compliance:
Long term medication should be sugar free
what to consider when antimicrobials are prescribed to pregnancy?
Assess the possible risks vs. benefits to
mother and foetus, though ultimately
mother is priority
Particular care needed in first trimester-organogenesis is maximally occurring
Mostly prescribed for maternal urinary
tract infections (UTIs) and respiratory tract
infections
what to consider when antimicrobials are prescribed to breast feeding mothers?
Antimicrobial agents enter milk by a process of
active or passive secretion
Known effects of orally delivered antibiotics on
gut flora, potentially long-lasting
Concentration of antimicrobial agent in serum of
baby is rarely close to that of the mother
Does it really matter ? It’s never ideal but:
Is the drug “safe” to give orally to kids anyway ?
Can we minimise exposure (timing, avoidance) ?
what to consider when antimicrobials are prescribed to elderly patients?
Older people are more susceptible to infection due to
impairment of their immune response system
Inflammatory/immune response may also be impaired
leading to more serious infective states
Factors to consider :
Reduction in renal function: Agents excreted by the kidney may accumulate in patients with renal failure e.g. gentamicin
Reduction in liver function
Change in lean body mass
Reduced blood flow to gut and liver
Antimicrobial drugs vary widely in cost
true of false?
true
considering Impact of resistance on choice of therapy, what is there a need for?
accurate prediction of efficacy
newer dosage regimens
newer antimicrobials
control measures
when is the use of antibiotics justified?
Serious or life-threatening infection or immunocompromised patient
Likely or proven polymicrobial infection
Risk of infection with resistant bacteria:
due to recent contact with healthcare environment
due to recent exposure to antibiotics or failed first-line
therapy
Known infection with resistant bacteria
Treatment failure of narrow spectrum agents.
how to start smart when prescribing antibiotics?
initially:
Make good choices: Is there an infection at all?
• TAKE SAMPLES before the drugs start
• Expected organism guides choice and dose
Location then tailors dosing further
Patient pharmacokinetics, allergies etc
Remember, high risk = Broad cover and Big doses
how make More SMART / FOCUS actions when prescribing antibiotics?
down the line:
Make an initial PLAN and WRITE it down
Document diagnosis and intentions in notes and on
charts.
If you’re not following guidelines, why not ?
What’s your review timetable?
When you’ve reviewed, document your findings and
ongoing plan
When you know exactly what you’re treating,
Use the most appropriate option (Stop, Switch IV to
Oral, Change, Continue, treat at home)
