Macrolides

Chapter 62


Macrolides






INDICATIONS


See Table 62-1 for specifics.



TABLE 62-1


Macrolide Indications with Dosage and Administration Recommendations





























































































































Drug Bacteria Site/Disease Dosage
erythromycin GABHS, S. pneumoniae URI mild to moderate, lower respiratory infection Adult: 250-500 mg qid × 10 days
  M. pneumoniae Respiratory tract Child: 20-50 mg/kg/day in divided doses × 10 days
  S. pyogenes, S. aureus Skin and skin structure Adult: 500 mg qid × 5-10 days
  B. pertussis Whooping cough Adult: 250-500 mg qid × 10 days
  C. diphtheriae Diphtheria; eradicate carriers Child: 20-50 mg/kg/day in divided doses × 10 days
  GABHS Prevention Adult: 500 mg qid × 14 days
      Child: 40-50 mg/kg/day in divided doses × 14 days
      500 mg q6h × 10 days
      250 mg bid
clarithromycin GABHS Pharyngitis, tonsillitis 250 mg q12h × 10 days
  H. influenzae, M. catarrhalis, S. pneumoniae Acute sinusitis 500 mg q12h × 14 days
  H. influenzae Acute exacerbation of COPD 500 mg q12h × 7-14 days
  H. parainfluenzae Acute exacerbation of COPD 500 mg q12h × 7 days
  H. influenzae CAP (pneumonia) 250 mg q12h × 7 days
  S. pneumoniae, M. pneumoniae, C. pneumoniae CAP (pneumonia) 250 mg q12h × 7-14 days
  Streptococcus, Staphylococcus Skin 250 mg q12h × 7-14 days
azithromycin S. aureus, S. pyogenes, S. pneumoniae, H. influenzae, M. catarrhalis, Legionella Acute exacerbation of COPD, CAP, pharyngitis, tonsillitis, skin Adult: 500 mg × 1 day, then 250 mg × 4 days
    Otitis media Child (>6 mo): 30 mg/kg (maximum, 1500 mg) × 1 dose, or 10 mg/kg (maximum, 500 mg) once daily × 3 days, or 10 mg/kg × 1 day, then 5 mg/kg (maximum, 250 mg) × 4 days
    CAP Child: 10 mg/kg × 1 day, then 5 mg/kg × 4 days
fidaxomicin C. difficile GI: nausea, vomiting, abdominal pain 200 mg po bid × 10 days
telithromycin S. aureus, Strep pneumoniae, H. influenzae, M. catarrhalis, Chlamydophila (Chlamydia) pneumoniae, Mycoplasma pneumoniae CAP 800 mg (two 400-mg tablets) once daily × 10 days
    Sinus 800 mg (two 400-mg tablets) once daily × 5 days
    Bronchitis, chronic or acute exacerbation 800 mg (two 400-mg tablets) once daily × 5 days


image


CAP, Community-acquired pneumonia; GABHS, group A β-hemolytic Streptococcus pyogenes.



Erythromycin, azithromycin, and clarithromycin are commonly used in primary care. They have primary indications and are used as an alternative to penicillin in sensitive patients. Erythromycin was derived from Saccharopolyspora erythraea (originally Streptomyces erythreus), found in the Philippines in 1952. Erythromycin is active against most pneumococci and group A β-hemolytic streptoccoci. It is also useful for atypical infections such as Legionella pneumophila, Mycoplasma pneumoniae, Corynebacterium diphtheriae, Chlamydia trachomatis, Listeria monocytogenes, Ureaplasma urealyticum, and some rickettsia. Susceptible gram-negative bacteria include Bordetella pertussis, Neisseria gonorrhoeae, and meningitis. The ketolide telithromycin was approved in 2004. A new drug, fidaxomicin (Dificid), entered the market in late 2011. It is indicated for Clostridium difficile diarrhea. A major limitation to erythromycin use is the frequent occurrence of GI side effects and drug interactions. However, azithromycin and clarithromycin rarely cause problematic GI side effects. Macrolides affect the cytochrome P450 3A4 system, thereby inhibiting the metabolism of certain drugs. A careful patient history of concurrent medications will aid in preventing adverse drug interactions.




Resistance


As macrolide use has increased, macrolide resistance also has increased. Three major mechanisms of resistance to the macrolides have been identified. The most common one is decreased permeability of the cell wall to macrolides. Some bacteria are able to pump the antibiotic out. The second mechanism, target site alterations, results from a genetic ability to decrease binding of the antibiotic to targets on the ribosome. Decreased binding confers a high degree of resistance. The third major mechanism is drug inactivation by enzymes. Use of macrolides increases the nasopharyngeal presence of macrolide and penicillin-resistant pneumococci. Macrolide-resistant Streptococcus is a problem in the treatment of community-acquired pneumonia and middle ear infections. About half of patients with macrolide-resistant infections had not taken antibiotics in the past 6 months. Group A strep resistance is increasing to up to 15% to 35% in some geographic areas. Streptococcus pyogenes, Staphlococcus aureus, Streptococcus viridans, Clostridium perfringens, and Haemophilus influenzae are developing increased resistance to macrolides.

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Jul 22, 2016 | Posted by in PHARMACY | Comments Off on Macrolides

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