Adverse effects of antituberculous drugs

What it is

The first-line drugs are isoniazid (INH), rifampin (RMP), pyrazinamide (PZA) and ethambutol (EMB), and the initial regimen is all four together. If the isolate is fully susceptible the ethambutol can be stopped, and pyrazinamide should be given for the first 2 months; after that only isoniazid and rifampin are given for the remainder of therapy, usually another 4 months. The same course is written elsewhere as 2 months of HRZE then 4 months of HR, where H is isoniazid, R is rifampicin, Z is pyrazinamide and E is ethambutol. A second standard regimen stands beside it, 2 months of HRZE then 4 months of HRE, and it applies only in countries with high levels of isoniazid resistance in new TB patients, or where isoniazid drug susceptibility testing in new patients is not done, or results are unavailable, before the continuation phase begins. The two phases are named and held on a mnemonic: the initial phase, the first 2 months, is RIPE, and the continuation phase is the next 4 months of rifampicin and isoniazid. In latent TB the options are 6 or 9 months of isoniazid monotherapy, three months of daily isoniazid plus rifampin, or four months of daily rifampin. The course is extended for some sites: spinal and bone disease 9 months, CNS 12 months, and where the patient does not respond to treatment. Patients with meningeal tuberculosis are treated for a prolonged period, at least 12 months, with the addition of steroids. CNS TB is set out as 12 months of 2HRZE + 10HR plus prednisolone 20-40 mg o.d. weaning over 2-4 weeks.