These are the mainstays of treatment of patients with bronchiectasis and infectious exacerbations. The route of antibiotic administration varies with the overall clinical condition, with most patients doing well on outpatient regimens. Some patients benefit from a set regimen of antibiotic therapy, such as therapy for 1 week of every month.
The choice of antibiotic is provider dependent, but, in general, the antibiotic chosen should have a reasonable spectrum of coverage, including the most common gram-positive and gram-negative organisms. Treatment of the patient who is more ill or the patient with CF often requires intravenous anti-Pseudomonas species coverage with an aminoglycoside, most often in combination with an antipseudomonal synthetic penicillin or cephalosporin. Aerosolized tobramycin has been found effective in patients with cystic fibrosis (CF).
Clarithromycin is a semisynthetic macrolide antibiotic that reversibly binds to P site of 50S ribosomal subunit of susceptible organisms and may inhibit RNA-dependent protein synthesis by stimulating dissociation of peptidyl t-RNA from ribosomes, causing bacterial growth inhibition.
Azithromycin (Zithromax, Zmax)
Azithromycin is an azalide, a subclass of the macrolide antibiotics. Following oral administration, it is absorbed rapidly and widely distributed throughout body. Its mechanism of action is interference with microbial protein synthesis.
Azithromycin is effective against a wide range of organisms, including the most common gram-positive and gram-negative organisms. It has additional coverage of so-called atypical infections, such as Chlamydia, Mycoplasma, and Legionella species. This agent is indicated for treatment of patients with mild-to-moderate infections, including acute bronchitic infections that may be observed with bronchiectasis.
Trimethoprim and sulfamethoxazole (Septra DS, Bactrim DS)
Trimethoprim-sulfamethoxazole is a synthetic combination antibiotic. Each tab contains 80 mg of trimethoprim and 400 mg of sulfamethoxazole. It is rapidly absorbed after oral administration. The mechanism of action involves blockage of 2 consecutive steps in biosynthesis of nucleic acids and proteins needed by many microorganisms.
This agent provides coverage for common forms of both gram-positive and gram-negative organisms, including susceptible strains of Streptococcus pneumoniae and Haemophilus influenzae. It is indicated in the treatment of acute and chronic bronchitic symptoms in patients with bronchiectasis.
Doxycycline (Doryx, Oraxyl, Vibramycin)
Doxycycline is a broad-spectrum, synthetically derived bacteriostatic antibiotic in the tetracycline class. It is an alternative agent for patients who cannot be given macrolides or penicillins.
Doxycycline is almost completely absorbed, concentrates in bile, and is excreted in urine and feces as a biologically active metabolite in high concentrations. It inhibits protein synthesis and, thus, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria. It may block dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
Fluoroquinolones should be used empirically in patients likely to develop exacerbation due to resistant organisms to other antibiotics. Levofloxacin is rapidly becoming a popular choice in pneumonia. It is the L stereoisomer of the D/L parent compound ofloxacin, the D form being inactive.
This agent is good for monotherapy, with extended coverage against Pseudomonas species and excellent activity against pneumococcus. It acts by inhibition of DNA gyrase activity. Bioavailability of the oral form reportedly is 99%.
Tobramycin is an aminoglycoside specifically developed for administration with a nebulizer system. When inhaled, it is concentrated in airways, where it exerts an antibacterial effect by disrupting protein synthesis. Tobramycin is active against a wide range of gram-negative organisms, including P aeruginosa. It is indicated for treatment of patients with CF and P aeruginosa infection.
A water-soluble injectable antibiotic of aminoglycoside group, gentamicin acts by inhibiting normal protein synthesis; it is active against variety of pathogenic organisms, including P aeruginosa. For treatment of Pseudomonas species, it is often used in combination with an antipseudomonal synthetic penicillin or cephalosporin.
In patients with bronchiectasis, gentamicin (or other aminoglycosides) may be indicated in setting of severe respiratory tract infection or CF. Dosing regimens are numerous; adjust dose based on creatinine clearance (CrCl) and changes in volume of distribution. Gentamicin may be administered IV or IM.
Amikacin irreversibly binds to the 30S subunit of bacterial ribosomes; it blocks the recognition step in protein synthesis and causes growth inhibition. It is indicated for gram-negative bacterial coverage of infections resistant to gentamicin and tobramycin. Amikacin is effective against P aeruginosa. Use patient's ideal body weight (IBW) for dosage calculation. The same principles of drug monitoring for gentamicin apply to amikacin.