The common drugs used in the second line of tuberculosis are mainly categorized into second-line injectable drugs, quinolones, and other core second-line drugs, as follows: 1. second-line injectable drugs: including amikacin, colistin sulfate and so on. 2. Quinolones: including ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin, gatifloxacin, and so on. 3. Other core second-line drugs: including cycloserine, propylthioisonicotinamide, ethylthioisonicotinamide, clofazimine, linezolid and so on. Second-line drugs are mainly used to combine the first-line drugs in case of relapse, drug resistance, or intolerance to the side effects of the first-line drugs. The choice of switching between first-line and second-line drugs should be decided by the doctor according to the results of drug sensitivity test and sputum examination, and should not be changed from first-line to second-line arbitrarily, so as not to cause adverse reactions.