Antibiotic Factors Flashcards
Empiric Therapy
broad spectrum antibiotics before pathogen identification
Critically ill patients
antibiotic therapy initiated immediately or concurrently with collection of diagnostic specimens
Bacterial endocarditis and osteomyelitis
may hold antibiotic therapy until appropriate testing done
Directed therapy
de-escalated to agent with narrowest effective spectrum of activity, after identification of pathogen is known
Considerations for empiric therapy
- knowledge of likely pathogens to cause specific infections
- anticipated antimicrobial susceptibility
- information from patient history and physical exam
Bactericidal (these effects can be specific to different organisms)
= organisms are killed by acting on the cell wall, cell membranes, or DNA
Bacteriostatic (these effects can be specific to different organisms)
inhibit bacterial replication without
killing the organism by inhibiting protein synthesis
Reasons for combination therapy
- broaden spectrum coverage for empiric therapy
- achieve synergistic bactericidal activity against a pathogen
- prevent emergence of resistance
Disadvantages of combination therapy
- increased cost
- greater risk of toxicity
- super infection with resistant bacteria
- antagonism
Selecting antimicrobial therapy efficacy
clinical and bacteriologic effect
FDA-approved vs. non-approved indications
many problems with newer agents since patients are usually excluded, (small sample sizes)
Selecting antimicrobial therapy in vitro microbiologic activity
spectrum of activity, susceptibility tests, resistance trends and mechanisms
selecting antimicrobial therapy pk
- absorption -> may be impaired by disease state, surgery, drug therapy
- distribution -> achievable in bloodstream, and sites of infection
- metabolic
- elimination -> not the same as metabolism
- tissue distribution (assessed via micro dialysis)
selecting antimicrobial therapy pd
- study of biochemical and physiological effects of drugs and their MOA.
- in-vitro concentration dependent activity
- in-vivo effects time above MIC
selecting antimicrobial therapy adverse effects
- risk/benefit analysis
problems with new agents are small sample sizes
selecting antimicrobial therapy drug-drug and drug food interactions
- isoenzymes that effect CYP450 (rifampin, voriconazole
- complexation/chelation (Fluoroquinolones and divalent/trivalent cations), tetracyclines, acronym ZICAM, enteral nutriotion products
Criteria for selection antimicrobial therapy
misuse
- prolonged empiric use without evidence of infection
- treatment of a positive culture in absense of infection
- failure to narrow empiric therapy when pathogen is identified
- prolonged prophylactic therapy
Excessive use of certain agents
Criteria for switch to oral therapy
overall clinical improvement lack of fever for 24 hours decreasing WBC count Functioning GI Tract Acceptable agent with good availability
Assessment of clinical failures
- reevaluate therapy after 2-3 days
- check for incorrect dx, incorrect antibiotic selection, and host factors
- incorrect organism
- laboratory errors
