15th March 2024

Tuberculosis treatment

The treatment regimen for tuberculosis (TB) depends on the resistance patterns. Standard treatment consists of six months of rifampicin and isoniazid, with two months of treatment with pyrazinamide and ethambutol. Multidrug-resistant (MDR) TB refers to an isolate having resistance to both rifampicin and isoniazid. Extensively drug-resistant (XDR) TB refers to an isolate having the same resistance as MDR TB, as well as a fluoroquinolone and either resistance to bedaquiline or linezolid.

Rifampicin

Rifampicin inhibits RNA polymerase and is used to treat mycobacterium, staphylococcus and legionella. It is recommended to monitor liver function tests due to the risk of hepatitis. Patients should be warned of the possibility of having orange and pink discolouration of secretions. Rifampicin is known to be an inducer of CYP2C9 and CYP3A4, decreasing the effectiveness of certain agents, including contraceptives, warfarin, phenytoin and sulfonylureas. Other adverse effects include an increased risk of C. difficile and rarely drug-induced haemolytic anaemia or disseminated intravascular coagulation.

Isoniazid

Isoniazid is useful for the treatment of mycobacteria through inhibition of mycolic acid synthesis. It can lead to peripheral neuropathy, which can be prevented with pyridoxine (B6) supplementation. Liver function tests should be monitored due to the risk of hepatitis and rarely it can lead to drug induced lupus.

Pyrazinamide

This agent is mainly used in the treatment of active TB. Adverse effects include sideroblastic anaemia, hepatotoxicity requiring monitoring of liver function tests and hyperuricemia, which can lead to the precipitation of gout.

Ethambutol

This agent is mainly used in the treatment of active TB. Patients starting this drug require regular visual checks as it can lead to visual disturbances secondary to optic neuritis. It can also cause peripheral neuritis, nephrotoxicity and hyperuricemia, which can lead to the precipitation of gout.

References

• Neil W Schluger, Scott K Heysell, Gerald Friedland, Treatment of drug-resistant pulmonary tuberculosis in adults (November 2021) <https://www.uptodate.com/contents/treatment-of-drug-resistant-pulmonary-tuberculosis-in-adults#H3240124502>.
• World Health Organisation, WHO announces updated definitions of extensively drug-resistant tuberculosis (27 January 2021) <https://www.who.int/news/item/27-01-2021-who-announces-updated-definitions-of-extensively-drug-resistant-tuberculosis>