PENICILLINS


I. PCN G:

  1. 1 million U PCN G = 600mg
  2. Preparations:
  1. Oral admin (PCN G Potassium): Not good (gastric destruction), so only used for mild/stabilized inf. or long-term prophylaxis; take 1h before or 2h after a meal
    1. Doses:
  1. <12yo, 40-80KU/kg/d divided into Q6-8h
  2. >12yo, 600K-1.6MU/d divided into TID-QID
  1. K or Na salts (Aqueous PCN G): can cause transiently high levels of K or Na when used parenterally; serum t-12 30min; eliminated by renal tubular secretion
  1. Can slow elimination by giving probenecid, which competitively inhibits active tubular secretion
  2. Doses:
  1. Babies <7d, 50KU/kg/d divided Q12h; Meningitis: 100-150KU/kd/d div'd Q8-12
  2. Babies >7d, 75KU/kg/d divided Q8h; Meningitis: 150-250KU/kg/d div'd Q6-8
  3. Kids, 50-250KU/kg/d divided into Q4h
  4. Adults, 300K-1.2MU/d, can give more if bad
  1. Procaine or Benzathine PCN G: For IM admin., produces sustained, low blood levels
  1. Don't give Procaine PCN IV! (cardiotoxic)
  2. n.b. There is a PO prep. of Benz. PCN G, but no indications exist! Also exist mixtures of Procaine & Benzathine; not much good for anything
  3. Doses
  1. Procaine 600K-1.2MU/d divided into 1-2 doses; in infants, 50KU/kg QD
  2. Benzathine
  1. Adults 1.2MU x 1
  2. Kids >27kg 900KU x 1
  3. Infants, Kids <27kg 50KU/kg x 1
  4. Benz. for endocarditis prophyl: 1.2MU Qmonth; for kids <10y, 600KU Qmonth (can also give PCN V PO)
  1. Adverse Rxns from PCN G:
  1. Allergic most common (n.b. some cross-sensitivity between PCNs & cephalosporins!)
  2. Convulsions can result from high-dose tx in neonates or pts w/renal dis. or rapid IV admin >20MU/d

II. PCN V:

  1. For PO admin.; more resistant to gastric destruction
  2. Similar antimicrobial spectrum to PCN G, except more active against gm-negs
  3. Doses
    1. Adults 125-500mg QID-6x/d
    2. If bad renal dis., don't give >1g/d
    3. Kids 25-50mg/kg/d divided Q6-8h (x10d for strep pharyngitis
    4. For endocarditis prophyl, 125-250mg BID
  1. Preparations: ?difference?
  1. PCN V
  2. PCN V-Potassium (V-K)

III. Ampi/Amox: better gm-neg. cov. (good for H. Flu, E. Coli, Branhamella; ok for Salmonella/Shigella; get higher & more stable levels with amox

IV. Beta-lactamase-resistant PCNs (for, e.g., Staph): methicillinc, diclox-, ox-, naf

V. Clavulanic acid, sulbactam are Beta-lactamase-binders