The antibiotic regimen for Lyme disease depends on the stage and manifestations of the disease, as well as on patient factors. Antimicrobial therapy typically focuses on Borrelia burgdorferi sensu lato, but should cover all likely pathogens in the context of the clinical setting. Coverage for co-infecting organisms, such as Ehrlichia species, should be considered, especially in patients with atypical clinical presentations.
Doxycycline is the preferred drug for oral treatment of Lyme disease in all patients except for pregnant and nursing women and children younger than 8 years of age.
Doxycycline is the drug of choice for early localized and early disseminated disease without evidence of central nervous system (CNS) involvement. It can be used for arthritis that is not persistent or recurrent. It has also been promoted for single-dose postexposure prophylaxis. Doxycycline has the key advantage of covering other tick-borne pathogens that may have been co-transmitted (eg, Ehrlichia species, Rickettsia species).
Doxycycline inhibits protein synthesis and thus bacterial growth by binding to the 30S and possibly the 50S ribosomal subunits of susceptible bacteria. This agent interferes with bacterial cell wall synthesis during active multiplication, causing cell wall death and resultant bactericidal activity against susceptible bacteria.
Tetracycline is used to treat gram-positive and gram-negative organisms, as well as mycoplasmal, chlamydial, and rickettsial infections. This agent inhibits bacterial protein synthesis by binding with the 30S and possibly 50S ribosomal subunits of susceptible bacteria. Tetracycline is an alternative drug to doxycycline. Because of its dosing schedule, doxycycline is preferred for compliance reasons; however, tetracycline may be less expensive.
Penicillins provide effective treatment of Lyme disease. These agents are used in patients who are intolerant of doxycycline and in pregnant women and children under the age of 8 years, in whom doxycycline is contraindicated. Intravenous formulations are used in patients who require parenteral therapy.
Penicillin VK inhibits the biosynthesis of cell wall mucopeptide. This agent is bactericidal against sensitive organisms when adequate concentrations are reached, and penicillin VK is most effective during the stage of active multiplication. Inadequate concentrations of this drug may produce a bacteriostatic effect only. In addition, penicillin VK can be used to treat erythema migrans, as it is safe in both pregnant and pediatric patients, although amoxicillin is used more commonly these patients.
Penicillin G is a penicillin antibiotic that inhibits cell-wall synthesis during active multiplication, causing cell wall death and resultant bactericidal activity against susceptible bacteria. This agent is an alternative drug to ceftriaxone in patients requiring parenteral therapy for CNS infection, persistent or recurrent arthritis, and/or carditis. The usefulness of penicillin G is limited by the need to administer it six times a day.
Amoxicillin is the drug of choice for oral treatment for pregnant or nursing women and children younger than 8 years. It is used for early localized and early disseminated disease without evidence of central nervous system (CNS) involvement. It can be used for arthritis that is not persistent or recurrent. This agent interferes with synthesis of cell wall mucopeptides during active multiplication, resulting in bactericidal activity against susceptible bacteria.
Macrolides are second-line agents for treatment of Lyme disease. They are appropriate only for patients with intolerance or contraindications to the use of tetracycline and beta-lactam antibiotics.
Use of erythromycin should be limited to patients who cannot take tetracyclines or beta-lactam antibiotics, as erythromycin is inferior to those agents for treatment of Lyme disease. Erythromycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
In children, age, weight, and severity of infection determine the proper dosage. When twice-daily dosing is desired, half the total daily dose may be taken every 12 hours. For more severe infections, double the dose.
Azithromycin is a second-line drug. Like erythromycin, this agent has excellent in vitro sensitivities, but mixed data exist regarding its clinical efficacy in early Lyme disease. Because of its once-daily dosing, azithromycin can be considered in pregnant patients who are allergic to beta-lactams and in patients in whom compliance is a major issue.
Clarithromycin is a macrolide antibiotic that inhibits protein synthesis by binding to the 50S ribosomal subunit. This drug is not first-line therapy but is an alternative agent for patients intolerant of doxycycline, amoxicillin, and cephalosporins.
Cephalosporins, 3rd Generation
Intravenously administered cephalosporins are drugs of choice for more severe manifestations of Lyme disease.
Ceftriaxone is a third-generation cephalosporin that is the preferred drug for intravenous therapy, as it has excellent activity against Borrelia burgdorferi and has favorable pharmacokinetics. It is the drug of choice for CNS infections (eg, meningitis, multiple cranioneuropathies), persistent (ie, minimal improvement within 7 d of initiating oral therapy) or recurrent arthritis, and carditis.
Ceftriaxone inhibits bacterial cell wall synthesis by binding to one or more penicillin-binding proteins. Bacteria eventually lyse because of ongoing activity of cell wall autolytic enzymes, while cell wall assembly is inhibited.
Cefotaxime is a third-generation cephalosporin that inhibits bacterial cell-wall synthesis. This agent is an alternative drug to ceftriaxone in patients requiring parenteral therapy.
Cephalosporins, 2nd Generation
Orally administered cefuroxime is an alternative to doxycycline, for patients with intolerance or contraindications to the use of tetracycline antibiotics.
Cefuroxime is a second-generation cephalosporin that is the only drug approved by the Food and Drug Administration (FDA) for use in Lyme disease. Cefuroxime is approved for use in adults. Its principal limitation is its expense. Cefuroxime binds to penicillin-binding proteins and inhibits the final transpeptidation step of peptidoglycan synthesis, resulting in cell wall death.
Some agents in this class can be used to supplement nonsteroidal anti-inflammatory drugs in patients with Lyme arthritis that is unresponsive to antibiotic therapy, as the synovial inflammation in these patients may represent an autoimmune response.  Aminoquinolines may impair complement-dependent antigen-antibody reactions.
The mechanism of action of hydroxychloroquine is unknown. This agent may impair complement-dependent antigen-antibody reactions; it inhibits locomotion of neutrophils and chemotaxis of eosinophils. Patients with rheumatic disease may take 4-6 months to show response to hydroxychloroquine; peak response takes several months.
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