Antibiotics Delivered by Aerosol
Antibiotics delivered by aerosol to treat
bacterial or fungal infections of the respiratory tract would theoretically reduce
systemic toxicity. However, disposition of the antibiotic, especially in the most
peripheral airways, may be impaired due to fall out during delivery (Ahrens, Pediatr
Pulmonol, 2:19, 1986) or mucus plugs that block access to the airways (Alderson, Clin
Pediatr, 23:553, 1984). Apart from the use of Ribavirin and pentamidine, no studies
have shown aerosolized antibiotics to be effective in treating pulmonary infections
(Manthous and Hall. Chest 1994; 106:560). One might imagine that aerosolized
antibiotics could be used in infants with extremely difficult IV access. In reviewing the
deposition of particles from jet nebulizers through 3 mm ET tubes, Kelly (Clin Chest
Med, 8:681, 1987) reported that at inspiratory flow rates of 7.5, 10, and 12.5 LPM,
the amount of aerosol deposited in the lung was 8.5%, 12%, and 30% respectively of the
administered dose. The amount deposited in the lungs increased with increasing ET tube
size. Recommendations are based on the extensive use of aerosolized antibiotics in
treating cystic fibrosis and case reports, controlled trials are lacking. Presumably the
high doses recommended are due to the small amount of drug that eventually reached the
lung as well as the age of the children treated. There are no specific recommendations for
infants or adults (Chest 1994; 106:560). If the antibiotics have significant
systemic toxicities, serum levels should be followed. Aerosolized antibiotics appear to be
more useful in controlling colonization rather than having the ability to eradicate a
pulmonic infection, and therefore may not be indicated for therapy. Use may also promote
emergence of antibiotic resistance. Although not in the lists below, both amphotericin (Am
Rev Resp Dis, 193:289, 1971) and vancomycin have been given by aerosol. Weathers (Pediatr
Infect Dis J 1990; 9:220-1) reported using a dose of 40 mg of vancomycin delivered by
nebulizer three times a day in an 11 kg child. The treatment course was 4 days. To
eradicate nasopharyngeal carriage of MRSA, vancomycin drops diluted in normal saline (60
mg/ml) were delivered intranasally, one drop in each nostril, four times a day.
Absorption of antibiotics from the bronchial tree is
usually quite low so that toxicity due to accumulation of the antibiotics would be
exceedingly rare. In the presence of inflammation of the airway, absorption may be
increased. Bronchospasm may occur as a result of delivering antibiotics by aerosol
(Wanner. Am Rev Respir Dis 1980; 122:79-103), but in the limited reports of
aerosolized antibiotics, the infants were reported to have few problems. It would be
prudent to obtain a random drug level of the antibiotics associated with potential
toxicities during treatment.
Gentamicin is available in an 80 mg/2 ml vial.
Aerosolized doses of 5 to 80 mg have been suggested. We would suggest using 40 mg diluted
to 2 ml using normal saline.
Vancomycin can be diluted in SWFI to produce a 50
mg/ml concentration. This concentration can be given as an aerosol or as nose drops. There
are no recommendations for an aerosolized dose but we currently would use 15 mg/kg diluted
to 2 ml and given two or three times a day.
Other antibiotics would only be given in even
more exceptional circumstances.