Editing Infections: Antibiotics (section)

==Characteristics of Antibiotics by Class==
===Aminopenicillins===
*Ampicillin and amoxicillin have been used often in the past for the treatment of UTIs, but the '''emergence of resistance''' in 40-60% of common urinary '''isolates has lessened the usefulness of these drugs (See Toronto antibiograms''')
*'''The effects of ampicillin and amoxocillin on the normal bowel and vaginal flora can''' predispose patients to reinfection with resistant strains and '''often lead to candida vaginitis'''
*'''The addition of the β-lactamase inhibitor clavulanate to amoxicillin greatly improves activity against β-lactamase–producing bacteria resistant to amoxicillin alone. However, its high cost and frequent gastrointestinal side effects limit its usefulness.'''
*'''The extended-spectrum penicillin derivatives (e.g., pivmecillinam, piperacillin, mezlocillin, azlocillin) retain ampicillin’s activity against enterococci and offer activity against many ampicillin-resistant gram-negative bacilli'''
*'''Safe for use in pregnancy'''
===Cephalosporins===
*'''In general, as a group, activity is high against Enterobacteriaceae and poor against enterococci'''
*First-generation cephalosporins have greater activity against gram-positive organisms, as well as common uropathogens such as E. coli and Klebsiella pneumoniae, whereas second-generation cephalosporins have activity against anaerobes. Third-generation cephalosporins are more reliably active against community-acquired and nosocomial gram-negative organisms than other β-lactam antimicrobials.
*Use of these broad-spectrum agents should be limited complicated infections and situations in which parenteral therapy is required and resistance to standard antimicrobial agents is likely.
*'''Safe for use during pregnancy'''
*'''Ceftriaxone is contraindicated in neonates'''
===Nitrofurantoin===
*'''Effective against common uropathogens'''; '''not effective against Pseudomonas and Proteus'''
*Rapidly excreted in the urine but '''does not obtain therapeutic levels in most body tissues. Therefore, not useful for upper tract and complicated infections.'''
*'''Minimal effects on the resident bowel and vaginal flora''' and has been used effectively in prophylactic regimens
*Acquired bacterial resistance is exceedingly low
*'''Pregnancy'''
**'''2017 American College of Obstetricians and Gynecologists recommendations'''§''':'''
***'''First trimester'''
****Consider and discuss with patients the benefits as well as the potential unknown risks of teratogenesis and fetal and maternal adverse reactions.
****'''Prescribing sulfonamides or nitrofurantoin in the first trimester is still considered appropriate when no other suitable alternative antibiotics are available.'''
***'''Second and third trimesters'''
****'''Can be used as first-line agents''' for the treatment and prevention of urinary tract infections and other infections caused by susceptible organisms.
***Contraindicated in patients with glucose-6-phosphate dehydrogenase deficiency, or in pregnant women identified to be at risk of this condition.
**'''CW12 page 1186-1187'''
***'''First and second trimester'''
****'''May be used safely in patients without glucose-6-phosphate dehydrogenase deficiency'''
***'''Third trimester'''
****'''Should be discontinued at 35 weeks''' because of an increased risk of hemolytic anemia in the neonate.
===Trimethoprim (TMP)-sulfamethoxazole (SMX)===
*'''TMP alone or in combination with SMX is effective against most common uropathogens; not effective against Enterococcus and Pseudomonas.'''
**TMP alone is as effective as the combination for most uncomplicated infections and may be associated with fewer side effects; however, the addition of SMX contributes to efficacy in the treatment of upper tract infection via a synergistic bactericidal effect and may diminish the emergence of resistance and attains therapeutic levels in most tissues.
*Advantages are inexpensive and have '''minimal adverse effects on the bowel flora'''
*Disadvantages are relatively common adverse effects, consisting primarily of rashes and gastrointestinal complaints.
*'''Trimethoprim blocks the tubular secretion of creatinine.'''
**Since creatinine is produced at a steady state, the serum creatinine will rise, but the GFR does not change
*'''<span style="color:#ff0000">TMP-SMX should be avoided during pregnancy because of early potential for teratogenicity and late potential for kernicterus'''
*'''<span style="color:#ff0000">Trimethoprim alone should be avoided in pregnancy due to risk of megaloblastic anemia; trimethoprim alone can be used in neonates'''
===Fosfomycin===
*Effective against most uropathogens; '''not effective against Pseudomonas'''
*Effective against the majority of gram-negative organisms and vancomycin-resistant Enterococcus (VRE)
*Limited cross-resistance between most other common antibacterial agents
*Shown to be effective as a single-dose agent when used as an empirical treatment for uncomplicated cystitis
*Generally well tolerated with low incidences of GI upset and headache and very rare adverse events
===Fluoroquinolones===
*'''Broad spectrum of activity'''
**'''Highly effective against Enterobacteriaceae and P. aeruginosa'''
**'''Activity is also high against S. aureus and S. saprophyticus, but, in general, anti-streptococcal coverage is marginal'''
**'''Modest activity against enterococcus'''
*'''Most anaerobic bacteria are resistant to these drugs; therefore, the normal vaginal and bowel flora are not altered'''
*'''Increasing rates of resistance due to indiscriminate use of these agents'''
*Not nephrotoxic, but renal insufficiency prolongs the serum half-life, '''requires dose adjustment in patients with creatinine clearances of <30 mL/min.'''
*'''<span style="color:#ff0000">Contraindicated in children, adolescents, and pregnant or nursing women due to concerns of damage to developing cartilage'''
*'''Drug interactions''':
**'''Rare increases in the anticoagulant effects of warfarin when taken with fluoroquinolones'''.
**'''Concomitant antacid''' (containing magnesium or aluminum)''', iron, zinc, or sucralfate use dramatically decreases oral absorption'''
**Antacids containing magnesium or aluminum interfere with absorption of fluoroquinolones.
**Certain fluoroquinolones (enoxacin and ciprofloxacin) elevate plasma levels of theophylline and prolong its half-life
**'''Avoid with other drugs that prolong QT interval, such as amiodarone'''