Use of gentamicin in children with cystic fibrosis

Antibiotic use in Cystic Fibrosis

Chronic pulmonary infections contribute significantly to the morbidity and mortality of patients with CF. The primary pathogens are Pseudomonas aeruginosa (PA) and Staphylococcus aureus. Hemophilus influenzae has been isolated from a significant number of patients also. A number of the β-lactam and aminoglycoside antibiotics reportedly have altered pharmacokinetic variables in CF. Therapy of acute pulmonary deterioration consists of intravenous antibiotics for two weeks. Antibiotic selection is based on culture and sensitivity results. Currently, the combination of a broad-spectrum penicillin and an aminoglycoside seems to provide the best results. Prophylactic antibiotics are effective if the primary isolates are sensitive to the agents used. Chronic PA infections are problematic because effective oral agents are not available. Aerosolized antibiotics do not improve results over adequate systemic therapy for acute exacerbations. Questions regarding optimal dosages, frequency, and duration of therapy remain.

Inhaled antibiotics in cystic fibrosis: a review

OBJECTIVE

To provide an overview of aerosol drug therapy, including physical considerations and aerosol drug delivery systems, and to review clinical experience with inhaled antibiotics in cystic fibrosis (CF) when used as adjunctive therapy to intravenous therapy for acute pulmonary exacerbations and chronic, suppressive therapy.

DATA SOURCES

A MEDLINE search (1966-1995) of English-language literature describing the use of inhaled antibiotics for the management of CF.

STUDY SELECTION AND DATA EXTRACTION

All articles were considered for possible inclusion in the review. Pertinent information as judged by the authors was selected for discussion.

DATA SYNTHESIS

The use of inhaled antibiotics as adjunctive therapy to systemic therapy for acute exacerbations did not improve pulmonary function tests, increase hospital discharge rate, or permanently eradicate sputum Pseudomonas. Clinical trials of inhaled antibiotics as suppressive therapy yielded variable results. Individually, four trials documented a significant improvement in pulmonary function, three trials documented a slower decline in pulmonary function, and four trials reported a reduced frequency of hospitalizations. However, the trials were unable to collectively document a prolonged beneficial effect of inhaled antibiotics on pulmonary function, sputum bacterial density, and frequency of hospitalizations.

CONCLUSIONS

Clinical trials conducted thus far suggest no role for inhaled antibiotics in the treatment of acute pulmonary exacerbations in patients with CF. Aerosolized antibiotics used as suppressive therapy may be useful in certain patients, but their use should be limited to select patients based on individual response to therapy. Additional long-term, well-controlled trials of inhaled antibiotics as suppressive therapy are needed before routine use can be recommended.

Local treatment of respiratory infections with antibiotics

Local administration of antibiotics for the treatment of respiratory infections has the potential advantage of reduced systemic toxicity and increased drug concentration at the site of infection. This article reviews the basic principles of pulmonary drug delivery using aerosols and the clinical efficacy of local antibiotic therapy of respiratory infections. Clinical studies have been conducted with locally administered aminoglycosides, penicillins, cephalosporins, and polypeptides. The results of these investigations and the pharmacokinetic aspects of pulmonary antibiotic delivery are summarized.

Antibiotic use in cystic fibrosis

Chronic pulmonary infections contribute significantly to the morbidity and mortality of patients with CF. The primary pathogens are Pseudomonas aeruginosa (PA) and Staphylococcus aureus. Hemophilus influenzae has been isolated from a significant number of patients also. A number of the beta-lactam and aminoglycoside antibiotics reportedly have altered pharmacokinetic variables in CF. Therapy of acute pulmonary deterioration consists of intravenous antibiotics for two weeks. Antibiotic selection is based on culture and sensitivity results. Currently, the combination of a broad-spectrum penicillin and an aminoglycoside seems to provide the best results. Prophylactic antibiotics are effective if the primary isolates are sensitive to the agents used. Chronic PA infections are problematic because effective oral agents are not available. Aerosolized antibiotics do not improve results over adequate systemic therapy for acute exacerbations. Questions regarding optimal dosages, frequency, and duration of therapy remain.

Netilmicin (Netromycin, Schering-Plough)

Netilmicin sulfate, the 1-N-ethyl derivative of sisomicin, is a new aminoglycoside recently released for use in Canada and not yet released in the U.S. Its place in therapeutics, compared with gentamicin (G), tobramycin (T), and amikacin (A), is not yet established. Preliminary work in animals has suggested a lower incidence of nephrotoxicity and ototoxicity than with other aminoglycosides, and in vitro work has suggested some activity against G/T-resistant organisms. However, netilmicin appears to be virtually identical to G,T, and A in antimicrobial spectrum (except for its poorer activity against P. aeruginosa), human toxicity, and clinical use. For G/T-resistant organisms, amikacin is still the aminoglycoside of choice. In summary, netilmicin has not been demonstrated to have significant advantages over other aminoglycosides (G,T,A), and it is more expensive; thus, its potential value is limited.

A double-blind controlled trial of anti-Pseudomonas chemotherapy of acute respiratory exacerbations in patients with cystic fibrosis

A double-blind controlled trail of anti-Pseudomonas chemotherapy was carried out in 24 exacerbations of pulmonary disease in patients with cystic fibrosis. Fifteen exacerbations were treated with oxacillin plus sisomicin and carbenicillin (treatment group); nine were treated with oxacillin alone (control group). The planned length of treatment was 14 days. The difference between the failure rate in the treatment group (3/15) and the control group (7/9) was statistically significant (P less than 0.015). The difference in improvement of forced expiratory volume in 1 second was also significant (P less than 0.025). At the end of the study, Pseudomonas aeruginosa was still present in the sputum of all nine patients in the control group, but was not isolated from six of the 15 patients in the treatment group. The data suggest a beneficial role for anti-Pseudomonas chemotherapy in the treatment of acute pulmonary exacerbations in patients with cystic fibrosis.

Gentamicin and tobramycin compared in the treatment of mucoid pseudomonas lung infections in cystic fibrosis

18 children with cystic fibrosis and mucoid pseudomonas lung infection were treated with courses either of gentamicin plus carbenicillin, or tobramycin plus carbenicillin, with 2 children each receiving two courses. 10 courses of gentamicin at a dose of 9 mg/kg per day plus carbenicillin at 800 mg/kg per day, and 10 courses of tobramycin at 9 mg/kg per day plus carbenicillin at 800 mg/kg per day were given. There was clinical and x-ray improvement in both groups of children, but there was no difference between the therapeutic benefit of either regimen. Pseudomonas aeruginosa was not cultured at the end of treatment after 15 of the 20 courses, but it returned in all but one patient within 3 months. Neither ototoxicity nor renal damage with these high doses of aminoglycoside was detected. P. aeruginosa had not been eliminated when 9 of these patients earlier had received courses of gentamicin in a dose of 6 mg/kg per day plus carbenicillin at 800 mg/kg per day. The results show that P. aeruginosa can successfully be eliminated or suppressed with high-dose aminoglycoside plus carbenicillin, but such elimination is usually short lived.

Optimal antibiotic therapy in bronchopulmonary infections

Therapy of bronchopulmonary infections has evolved in the past 30 years. Only in the therapy of pneumococcal infections have, precise dosage programs been developed. Therapy of pneumococcal infection is optimal with penicillin G in low dosage. None of the newer agents has altered morbidity or mortality. The best agent for the treatment of pneumonia due to Staphylococcus aureus or members of the Enterobacteriaceae has not been established. Use of combination therapy consisting of an anti-Pseudomonas penicillin and an aminoglycoside has been shown to offer the greatest success in the treatment of Pseudomonas pulmonary infections. The optimal antibiotic and dosage program for the treatment of acute bacterial exacerbations of chronic bronchitis has yet to be defined. Further comparative studies of the chemotherapy of pulmonary infections are necessary.

Evaluation of long term tobramycin therapy in patients with cystic fibrosis and advanced pulmonary disease

To nine cystic fibrosis patients with chronic bronchopulmonary infection of severely damaged lungs invaded by Pseudomonas aeruginosa, eleven courses of prolonged tobramycin treatment (5 mg/kg/day) for four to 16 weeks were administered. Pulmonary symptoms improved and a better quality of life was achieved in all but one patient. Objective parameters (chest X-ray, pulmonary function tests) changed to a lesser extent. In only one patient was Pseudomonas eradicated from the sputum but reappeared after discontinuation of therapy. In the rest of the patients Pseudomonas was significantly suppressed or replaced by other pathogens. Four patients showed rises of antibody titres to Candida and two to Aspergillus fumigatus. No nephrotoxic side effects were observed, but vestibular function was reversibly impaired in one patient without corresponding clinical symptoms. No bacterial resistance to tobramycin was observed during therapy.