Formulation and efficacy of liposome-encapsulated antibiotics for therapy of intracellular Mycobacterium avium infection.

Mycobacterium avium is an intracellular pathogen that can invade and multiply within macrophages of the reticuloendothelial system. Current therapy is not highly effective. Particulate drug carriers that are targeted to the reticuloendothelial system may provide a means to deliver antibiotics more efficiently to M. avium-infected cells. We investigated the formulation of the antibiotics ciprofloxacin and azithromycin in liposomes and tested their antibacterial activities in vitro against M. avium residing within J774, a murine macrophage-like cell line. A conventional passive-entrapment method yielded an encapsulation efficiency of 9% for ciprofloxacin and because of aggregation mediated by the cationic drug, was useful only with liposomes containing < or = 50 mol% negatively charged phospholipid. In contrast, ciprofloxacin was encapsulated with > 90% efficiency, regardless of the content of negatively charged lipids, by a remote-loading technique that utilized both pH and potential gradients to drive drug into preformed liposomes. Both the cellular accumulation and the antimycobacterial activity of ciprofloxacin increased in proportion to the liposome negative charge; the maximal enhancement of potency was 43-fold in liposomes of distearoylphosphatidylglycerol-cholesterol (DSPG-Chol) (10:5). Azithromycin liposomes were prepared as a freeze-dried preparation to avoid chemical instability during storage, and drug could be incorporated at 33 mol% (with respect to phospholipid). Azithromycin also showed enhanced antimycobacterial effect in liposomes, and the potency increased in parallel to the moles percent of negatively charged lipids; azithromycin in DSPG-Chol (10:5) liposomes inhibited intracellular M. avium growth 41-fold more effectively than did free azithromycin. Thus, ciprofloxacin or azithromycin encapsulated in stable liposomes having substantial negative surface charge is superior to nonencapsulated drug in inhibition of M.avium growth within cultured macrophages and may provide more effective therapy of M.avium infections.

Evaluation of intravenous ciprofloxacin in patients with nosocomial lower respiratory tract infections. Impact of plasma concentrations, organism, minimum inhibitory concentration, and clinical condition on bacterial eradication.

Fifty patients with gram-negative lower respiratory tract infections were treated with intravenous ciprofloxacin to evaluate efficacy and safety. Relationships between individual pharmacokinetics and clinical and bacteriologic outcome were studied. Ciprofloxacin concentrations in plasma were determined by high-performance liquid chromatography. Respiratory secretion cultures were obtained daily to determine the eradication day of the infecting organism. Susceptibility (minimum inhibitory concentration) to ciprofloxacin and other antimicrobials was determined using standard microdilution techniques. The mean age of the patients was 70 years. They had multiple underlying diseases, and two thirds of them were ventilator dependent at entry. Approximately 50% of the patients had failed previous treatment for the same infections. Patients infected with Enterobacteriaceae or Haemophilus influenzae with minimum inhibitory concentrations of less than 0.25 mg/L responded well to intravenous ciprofloxacin therapy (200 mg every 12 hours). The organisms were eradicated from sputum cultures usually within 1 day after ciprofloxacin therapy was started. Most clinical failures occurred in patients who were infected with Pseudomonas aeruginosa and had multiple underlying diseases. Pseudomonas aeruginosa was isolated from 10 patients with pneumonia, 2 patients with lung abscess, and 1 patient with bronchiectasis. The Pseudomonas isolate acquired resistance during ciprofloxacin treatment in 7 patients with pneumonia and in all of the remaining 3 patients. We conclude that ciprofloxacin is safe and effective at a dosage of 200 mg administered intravenously every 12 hours for nosocomial lower respiratory tract infections caused by Enterobacteriaceae or Haemophilus species. Many patients who had failed previous antibiotic treatment for Enterobacteriaceae infections had good clinical response to ciprofloxacin therapy. Studies using either higher dosages of ciprofloxacin or combination therapy should be conducted to determine if acquired resistance can be avoided in Pseudomonas infections.

Oral ciprofloxacin in the treatment of serious soft tissue and bone infections. Efficacy, safety, and pharmacokinetics.

Forty-eight patients were enrolled in a clinical study of oral ciprofloxacin for the treatment of soft tissue or bone infections. Patients received 500 to 750 mg of ciprofloxacin every 12 hours. In the predominantly older population studied, there were 13 patients with osteomyelitis, 24 diabetic patients with soft tissue infection and probable osteomyelitis, and 11 patients with other soft tissue infections. Infecting pathogens included Pseudomonas aeruginosa in 25 patients, Serratia species in nine patients, Staphylococcus aureus in 13 patients, and other aerobic gram-negative rods in 21 patients. Clinical response (defined as resolution or improvement) was noted in 84 percent of patients with non-diabetic osteomyelitis, in 79 percent of patients with diabetic infections, and in 91 percent of patients with soft tissue infections. Microbiologic outcome was very favorable in 75 percent of cases, and Pseudomonas responded as well as any other pathogen. Pharmacokinetic properties of ciprofloxacin were evaluated in 12 patients, and the data were analyzed using both compartmental and non-compartmental analyses. Mean values for compartmental rate constants (hours-1) were as follows: absorption rate constant = 1.15; intercompartmental rate constants, k12 = 0.48, and k21 = 0.58; elimination rate constant = 0.46; distribution rate constant = 1.31; and terminal elimination rate constant = 0.19. The apparent volume of distribution at steady state/bioavailability was 196 liters and total body clearance/bioavailability was 45.9 liters/hour. The mean time to peak concentration was 1.3 hours. The mean peak concentration as determined by compartmental fitting (2.4 micrograms/ml) underestimated the observed peak (3.2 micrograms/ml) by 24.8 percent. Clearance of ciprofloxacin was similar regardless of the method used to fit the data, whereas the volume of distribution was significantly different when the two analysis techniques were compared. Ciprofloxacin was well tolerated, with the most frequent adverse reactions being rash, gastrointestinal intolerance, and increased levels of liver enzymes, each of which occurred in five patients.

Ciprofloxacin and norfloxacin, two fluoroquinolone antimicrobials.

The chemistry, mechanism of action, antimicrobial spectrum, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of ciprofloxacin and norfloxacin are reviewed, and mechanisms of antimicrobial resistance and drug and laboratory interactions are described. Norfloxacin is the first antimicrobial in the fluoroquinolone class to be marketed in the United States; ciprofloxacin is under investigation in clinical trials. The fluoroquinolones are structurally related to nalidixic acid. The activity and spectrum are enhanced by the addition of 6-fluoro and 7-piperazino substituents. Quinolone antimicrobials appear to inhibit DNA gyrase, an enzyme specific and essential for all bacteria, as their primary mechanism of action. As a result, DNA synthesis is inhibited. Ciprofloxacin and norfloxacin are active against gram-negative enteric bacteria, Pseudomonas aeruginosa, Haemophilus influenzae, and Neisseria gonorrhoeae. Ciprofloxacin has good activity against Staphylcoccus spp., including methicillin-resistant Staph. aureus. Norfloxacin generally is less potent than ciprofloxacin, particularly against Ps. aeruginosa and Staph. aureus. Peak concentrations occur about one to two hours after an oral administration of either drug. Both drugs are widely distributed in body fluids and tissues and are eliminated by renal excretion, metabolism, and biliary excretion. Dosage reductions are required in severe renal dysfunction. Ciprofloxacin and norfloxacin are effective agents for treating urinary-tract infections, including infections caused by Ps. aeruginosa. The recommended dosage of norfloxacin for urinary-tract infections in adults is 400 mg orally every 12 hours; the drug should be given for 7 to 10 days in uncomplicated infections and for 10 to 21 days in complicated ones. The fluoroquinolones may be useful for treating chronic bacterial prostatitis. Ciprofloxacin is potentially useful for treating sexually transmitted diseases. Ciprofloxacin is active against N. gonorrhoeae, including beta-lactamase-producing strains and strains that are resistant to tetracycline, and Chlamydia spp. Use of ciprofloxacin for treating gastrointestinal infections and for selective decontamination of the gastrointestinal tract is promising. In open studies, ciprofloxacin has been effective against a variety of infections caused by susceptible organisms. Resistance to ciprofloxacin has developed during treatment of infections caused by Ps. aeruginosa, Staph. aureus, and Serratia marcescens. The most frequently reported adverse effects of either drug are gastrointestinal complaints, headache, and dizziness.(ABSTRACT TRUNCATED AT 400 WORDS)