Quinolones Ciprofloxacin Levofloxacin and Ofloxacin

Most of the fluoroquinolones antibiotics (see Chapter 44) have activity against M. tuberculosis and M. avium-intracellulare. Ciprofloxacin, ofloxacin, and levofloxacin inhibit 90% of the strains of susceptible tubercula bacilli at concentrations of less than 2 ^g/mL. Levofloxacin is preferred because it is the active l-optical isomer of ofloxacin and is approved for once-daily use. The quinolones act by inhibition of bacterial DNA gyrase. Resistance is the result of spontaneous mutations in genes that either change the DNA gyrase or decrease the ability of the drug to cross the cell membrane.

Quinolones are important recent additions to the therapeutic agents used against M. tuberculosis, especially in MDR strains. Clinical trials of ofloxacin in combination with isoniazid and rifampin have indicated activity comparable to that of ethambutol. In addition, quinolones, particularly ciprofloxacin, are used as part of a combined regimen in HIV-infected patients.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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