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Antibiotic Therapy
· Factors in Choosing an Antibiotic
· Clinical syndrome
· Host characteristics
· Focused history
· Antibiotic characteristics
Assessment of Clinical Syndromes
· Identify predominant symptoms and signs
· Determine the site of infection
· Identify disease process
· Determine likely causative organisms
· Identify likely susceptibility pattern
Host Characteristics
· Age
· Underlying conditions
· Medical devices
· Nutritional status
· Travel
· Exposures
· Immunizations
· Drug abuse
· Sexual activity
Antimicrobial Selection Factors
Spectrum of activity
Absorption
Distribution
Metabolism
Excretion
Adverse Effects
Safety
Routes of administration
Drug-drug interactions
Cost
Palatability
Effect on Resident Flora
Selective Pressure on environment
General Principles of Antibiotic Therapy
· May initiate with broad spectrum awaiting culture results
· Obtain pertinent cultures to narrow therapy
· Use narrowest spectrum as possible
Penicillins
Agent | Activity | Clinical Uses |
Penicillin G | oral anaerobes | Gp A streptococcus pharyngitis |
Penicillin V | streptococci | RF prophylaxis |
Benzathine | Eikenella | Syphilis |
Procaine |
Pasteurella
Treponema |
aspiration
pathogen specific |
Penicillin - otitis media, pharyngitis, sinusitis Adverse Effects
· Allergic reactions
· Hemolytic anemia
· Interstitial nephritis
· Seizures and hyperkalemia in patients with underlying renal disease
Penicillinase-Resistant Penicillins
Agents | Activity | Clinical Uses |
Methicillin otitis media, pharyngitis, sinusitis
Nafcillin Oxacillin Cloxacillin Dicloxacillin |
S. aureus
S. epidermidis less active for penicillin suscepti ble bacteria |
S. aureus infec tions |
Adverse Effects of Penicillinase Resistant Penicillins
· Neutropenia - dose and duration related
· Cholestasis and cholestatic jaundice
· Interstitial nephritis - most common with methicillin
· Poor palatability of oral preparations (dicloxacillin and cloxacillin)
Aminopenicillins
Agents | Activity | Clinical Uses |
Ampicillin
Amoxicillin |
Penicillin suscep tible
Some GNR Enterococcus Listeria H influenzae Borrelia |
Otitis media
Sinusitis |