Carbenicillin in patients with cystic fibrosis: clinical pharmacology and therapeutic evaluation

Inhaled antibiotics beyond aminoglycosides, polymyxins and aztreonam: A systematic review

We sought to evaluate published evidence regarding clinical or microbiological outcomes related to the use of inhaled antibiotics other than aminoglycosides, polymyxins and aztreonam. A systematic search of PubMed and Scopus databases as well as bibliographies of eligible articles was performed. In total, 34 eligible studies were identified. Among several inhaled β-lactams, ceftazidime was used with varying success in the prevention and treatment of ventilator-associated pneumonia (VAP) and improved clinical outcomes in chronic Pseudomonas aeruginosa lower respiratory tract infections (LRTIs) in patients with cystic fibrosis (CF) or bronchiectasis. Inhaled vancomycin, as an adjunctive therapy, was effective in treating Gram-positive VAP, whilst inhaled levofloxacin, ciprofloxacin and an inhaled combination of fosfomycin and tobramycin were associated with improved microbiological or clinical outcomes in chronic LRTI in patients with CF or bronchiectasis. In conclusion, published evidence is heterogeneous with regard to antibiotics used, studied indications, patient populations and study designs. Therefore, although the currently available data are encouraging, no safe conclusion regarding the effectiveness and safety of the drugs in question can be reached.

Shifting patterns of inhaled antibiotic use in cystic fibrosis

RATIONALE

Antibiotic inhalation has become widely accepted as a standard treatment for cystic fibrosis (CF) airway infection. We assessed the prevalence and context of inhaled antibiotic use in the North American CF population. Our working hypothesis was that a shift from acute to chronic use of inhaled antibiotics has coincided with increased prevalence of use among CF patients.

METHODS

Descriptive statistics were collected for 30,833 patients enrolled in the Epidemiologic Study of CF (ESCF) during 1996 through 2005. A multivariate analysis was performed on data from a subgroup of 18,021 patients enrolled in ESCF during 2003 through 2005.

RESULTS

The prevalence of inhaled antibiotic use in the North American CF population increased during 1996 through 2005 due to increased chronic use, while acute use to treat pulmonary exacerbations decreased. In 2005, 50% of CF patients used inhaled tobramycin and 9% used inhaled colistin chronically; most of the latter used both agents concurrently. Airway obstruction severity and airway infection status were predictors of inhaled antibiotic use.

CONCLUSIONS

Increased chronic use and decreased acute use of inhaled antibiotics presumably reflect a shift toward more proactive management of airway infections in the North American CF population. The effects of these usage patterns on long-term clinical outcomes and emergence of antibiotic-resistant Pseudomonas aeruginosa strains warrant further study.

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.

Nebulized antibiotics in cystic fibrosis

Nebulization is a useful administration route in cystic fibrosis (CF) as it delivers antibiotics directly to the endobronchial site of infection and is associated with decreased toxicity because of limited systemic absorption. It is assumed that the concentration of antibiotics in bronchial secretions should be as high as 10 times the minimum inhibiting concentration to allow penetration of antibiotics into biofilms, suppress inhibitory factors and promote bactericidal effectiveness. However, effective aerosol delivery is compromised by nebulizers with limited capacity to produce particles of a size in the respirable range. Three antibiotics are commonly used for inhalation: tobramycin, amikacin and colistin (colomycin). Placebo-controlled studies evaluating antibiotic aerosol maintenance in stable patients chronically infected with Pseudomonas aeruginosa indicate a significant improvement of lung function and a reduction of the number of hospital admissions for an acute exacerbation of CF. TOBI is a recently marketed preservative- and sulfate-free formula of tobramycin, specially designed for diffusion in the bronchioles and optimal tolerance. A wide-scope study involving 520 patients compared TOBI (300 mg twice daily; n = 258) with placebo (n = 262) for three 28-day cycles with each cycle separated by a 28-day period of no treatment. Respiratory function was significantly improved as early as in the second week and remained so for the rest of the trial even during periods without aerosol treatment. There was also a parallel decrease in the relative risk of hospitalization, the number of days of hospitalization and the number of days on intravenous antipyocyanic treatment. Toxicity studies carried out so far have shown no renal or ototoxicity with nebulized tobramycin. Introduction or selection of resistant bacteria is relatively rare but remains a matter of concern. Aerosol maintenance treatment with an appropriate antibiotic in a high enough dosage can be recommended for patients with CF who are chronically infected with P. aeruginosa.

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.

Clinical pharmacology of antibiotics and other drugs in cystic fibrosis

The disposition of many drugs in cystic fibrosis is abnormal. In general, changes in pharmacokinetics include: increased volume of distribution, decreased plasma concentration, and enhanced renal and sometimes non-renal elimination of drugs. Pathophysiology of the disease important for drug disposition includes: (a) hypersecretion of gastric acid and duodenal secretions which are of small volume, viscous and low in bicarbonate; (b) increased intestinal permeability to some sugars and probe substances; (c) hypergammaglobulinaemia and sometimes hypoalbuminaemia; (d) significant elevation of free fatty palmitoleic acid level and decreased low-density and high-density serum lipoproteins; (e) an average increase by 30 to 45% in plasma volume in patients with cystic fibrosis who have moderately severe pulmonary disease, right ventricle hypertrophy and dilatation, which occurs in 15 to 35% of patients with a Shwachman score of 81 to 100; (f) abnormal bile acid metabolism and enterohepatic recirculation; and (g) enlarged kidneys and glomerulomegaly with increased glomerular filtration rate, tubular clearance and urine flow rate in some patients with cystic fibrosis. Delayed absorption from the gastrointestinal tract has been reported in patients with cystic fibrosis for cloxacillin, epicillin, clindamycin, ciprofloxacin and probably for cephalexin, para-aminobenzoic acid and chloramphenicol. A possible increased absorption was reported for cimetidine. Of 7 drugs studied only theophylline had significantly decreased plasma protein binding. An increased volume of distribution and increased renal clearance reported for several drugs is caused mainly by increases in plasma volume and urine flow rate in many of these patients. Possible increased elimination of some drugs in bile (which probably results from bile acid malabsorption) and in bronchial secretions (which are abundant in some cystic fibrosis patients with acute pulmonary infection) may explain enhanced non-renal elimination of these drugs. The metabolism of cimetidine in cystic fibrosis was reported not to be changed significantly compared to control subjects.

Clinical features, survival rate, and prognostic factors in young adults with cystic fibrosis

The medical records of 142 patients with cystic fibrosis were reviewed. The patient group included 78 males and 64 females; three patients were black. Periods of observation ranged from two to 25 years (mean, 14.5 years). The analysis focused on clinical evaluation at age 18 years and included information gained at an earlier age. Evaluation at age 18 years was based on Shwachman and Kulczycki's (S-K) scoring system, Brasfield chest roentgenographic scoring system, pulmonary function measurements, height-adjusted weight percentile, sputum bacteriologic results, number of hospitalizations for treatment of pulmonary infections prior to the age of 18 years, time of onset of clubbing, and frequency of complications. There were no significant differences between the sexes in clinical features. Median survival from the time of diagnosis to the conclusion of the study period (1955 to 1984) was 22 years for females and 25 years for males (NS). Median length of survival beyond the age of 18 years was eight years for females and 12 years for males (NS). Stepwise logistic regression and Cox regression analysis applied to 11 variables identified the S-K clinical score at 18 years of age as the best predictor of survival to the age of 23 years. The median durations of survival after the age of 18 years for patients with clinical scores of 30 to 49, 50 to 64, and 65 to 75 at age 18 were five, seven and a half, and 12 years, respectively (p less than 0.0001). Low clinical score, low weight percentile, and Pseudomonas cepacia colonization of the lower respiratory tract at the age of 18 years indicated a poor prognosis. On the other hand, high clinical score, good weight percentile, and colonization with Staphylococcus aureus alone were likely to be found in patients with mild disease and an increased likelihood of long-term survival with preserved pancreatic function.

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.

Infection in patients with cystic fibrosis

Cystic fibrosis is the most common lethal genetic disease of Caucasians. The disease affects the exocrine gland secretions throughout the body, and as a result, major pathologic changes develop in the pancreas and in the bronchi. Obstruction of the respiratory airways results in chronic infection, and in time, this leads to progressive deterioration of lung function. In the initial stages of the disease, usually during infancy, infection with Staphylococcus aureus plays an important role. Hemophilus influenzae infections are also common. As the disease progresses, infection with Pseudomonas aeruginosa develops. Exacerbation of bronchopulmonary infection is often initiated by respiratory viral or mycoplasmal infection, with superimposed S. aureus and P. aeruginosa infections contributing to the severity of the infection. Frequent courses of antibiotic therapy are usually required, and some patients may have to receive antibiotics continuously. Oral cephalosporins, ampicillin, and the combination of trimethoprim/sulfamethoxazole are commonly used for relatively mild infections. In the treatment of exacerbation of infection, intravenous penicillinase-resistant penicillins and anti-Pseudomonas antibiotics are the drugs of choice. For Pseudomonas infections, ticarcillin, carbenicillin, the ureidopenicillins, and the aminoglycosides are indicated. The combination of an anti-Pseudomonas penicillin and an aminoglycoside are most commonly used. Of the third-generation cephalosporins, ceftazidime appears to be the most efficacious. The quinolones (such as ciprofloxacin) are also active against P. aeruginosa, and preliminary studies of these drugs in patients with cystic fibrosis appear to indicate that they are as efficacious as the already available antibiotics. In many centers, Pseudomonas cepacia has emerged as a serious problem in patients with cystic fibrosis. This organism tends to develop resistance to multiple antibiotics. In some centers, infection with P. cepacia has been associated with a severe, frequently fatal, pneumonia.

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.

125I-Clq-binding and specific antibodies as indicators of pulmonary disease activity in cystic fibrosis

We studied the incidence and levels of circulating immune complexes by the 125I-Clq-binding assay in patients with cystic fibrosis in relation to clinical respiratory status and specific IgG and IgE antibodies to Pseudomonas aeruginosa. Staphylococcus aureus, Aspergillus fumigatus, and Candida albicans. Overall prevalence of CIC was 43%, but 86% of serially studied patients had evidence of CIC at some time. Patients with acute respiratory exacerbations and deteriorating pulmonary function had a higher incidence of CIC (76%) as compared to stable patients (36%, P less than 0.01), as well as significantly higher levels of CIC. Acute exacerbations were also associated with significant increases in IgG antibody to Pseudomonas (P less than 0.005) but not in other antibodies. CIC did not correlate with Pseudomonas-specific IgG nor with any other specific antibody studied. A variety of age-related differences in specific antibody levels were seen. The episodic appearance of CIC is common in CF and is usually associated with exacerbation of lung disease.

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.

Chemotherapy of chronic infections with mucoid Pseudomonas aeruginosa in lower airways of patients with cystic fibrosis

The bacteriological effect of chemotherapy against Pseudomonas aeruginosa (Ps.ae.) in lungs of patients with cystic fibrosis is reviewed. During a 5-year period 49 children and adults were treated with 190 courses of different antibiotics. The mucoid strains of Ps.ae. disappeared in 72.0% of the courses in which a combination of tobramycin and carbenicillin was employed. Tobramycin given alone had only bacteriological effect in 26.6% of the courses. Colimycin alone or in combination with carbenicillin had no effect. In 18 patients who received subsequent courses of tobramycin and combination of tobramycin and carbenicillin a significant difference in favour of the combination therapy was found, also in cases with many precipitins against Ps.ae. in serum. In 74.5% of the initially successful courses the patients were recolonized with Ps.ae. within 1 month. No nephrotoxic or ototoxic side effects were demonstrated in spite of the high doses of tobramycin (10 mg/kg/24 h) emmployed and the repeated courses.

Treatment of pulmonary infections in patients with cystic fibrosis: a comparative study of ticarcillin and gentamicin

The effectiveness of ticarcillin against Pseudomonas aeruginosa in acute exacerbations of pulmonary infection in patients with cystic fibrosis was evaluated. Seventy-one percent of patients treated with ticarcillin alone responded favorably. The response rate was similar in patients treated with a combination of ticarcillin plus gentamicin or with gentamicin alone. Severity of the underlying disease was the most important determinant of response to treatment. Ticarcillin-resistant organisms were recovered during treatment in 50% of patients who received this drug; recovery of them was not prevented by the inclusion of gentamicin in the therapeutic regimen nor did they interfere with clinical improvement. The ticarcillin-resistant strains persisted at follow-up, two to six months after completion of therapy, in only one of ten patients. No serious toxicity to ticarcillin was noted during the study period.

Pseudomonas carrier rates of patients with cystic fibrosis and of members of their families

The majority (86.6%) of patients with cystic fibrosis were found to be carriers of Pseudomonas aeruginosa. None of them, however, carried P. aeruginosa in their nares. In contrast, none of the non-CF family members of the patients with CF were carriers of P. aeruginosa. For example, only 4 of 468 cultures from skin, throat, and nares of the family members were positive for P. aeruginosa. Isolations of P. aeruginosa from the same CF patients were often of the same pyocine type. No specific pyocine type of P. aeruginosa was predominant in patients with CF. Isolations of P. aeruginosa from siblings with CF may or may not be of the same pyocine type as that of the family proband. Colonization of a patient with CF by P. aeruginosa is not a threat to the non-CF members of the family.

Colonization by Enterobacteriaceae of the respiratory tract of children with cystic fibrosis of the pancreas and their antibody response

Of 72 patients with fibrosis, 49 harbored Enterobacteriaceae in the respiratory tract, including Escherichia coli, Klebsiella, and Enterobacter. Colonization by two to four genera was documented in 29 subjects. Staphylococcus aureus was recovered from 44 of these 49 patients. The distribution of serogroups of E. coli was similar to that seen in patients with urinary tract infection. Antibody response against the O antigens of the patients' own Enterobacteriaceae was documented in 29 of these 49 children and encountered more often in patients with severe disease. Colonization by Enterobacteriaceae in the absence of Pseudomonas aeruginosa was seen more frequently in children with the mild form of the illness.