A Textbook of Clinical Pharmacology and Therapeutics

PRINCIPLES OFMANAGEMENT OFMYCOBACTERIUMTUBERCULOSISINFECTIONS 335

rifampicin,pyrazinamideandethambutol(orstreptomycin)

is administered for the first two months, followed by

rifampicin and isoniazid for a further four months.

Ethambutoland/orstreptomycinmay be omitted in patients

who are at relatively low risk of carrying multi-drug resistant

(MDR)M. tuberculosis, which includes 99% of the UK-born pop-

ulation. However, the initial use of four drugs is advisable in

HIV patients and in immigrants from countries where MDR M.

tuberculosisinfection is likely. The initial four-drug combination

therapy should also be used in all patients with non-tuberculous

mycobacterial infection, which often involves organisms that

are resistant to both isoniazidandpyrazinamide. Patients

withopen active tuberculosis are initially isolated to reduce the

risk of spread, but may be considered non-infectious after 14

days of therapy. Those with MDR M. tuberculosisare isolated

PRINCIPLES OF MANAGEMENT OF

MYCOBACTERIUM TUBERCULOSIS

INFECTIONS

The treatment of pulmonary tuberculosis is summarized in
Figure 44.2. Successful M. tuberculosistherapy requires an initial
combination with at least three (and often four) drugs. The use
of several drugs reduces the risk of ‘missing’ the occasional
drug-resistant individual which will multiply free of competi-
tion from its drug-sensitive companions. The multi-drug strat-
egy is therefore more likely to achieve a cure, with a low relapse
rate (0–3%) and reduced drug resistance. The British Thoracic
Society now recommends standard therapy for pulmonary
tuberculosis for six months. A combination of isoniazid,

Risk of

carrying

multi-drug resistant

M. tuberculosis

Non-

tuberculous

mycobacterial

infection?

HIV-

positive or

other cause of

immune

suppression

Commence treatment

with 3 drugs

• Isoniazid


• Rifampicin


• Pyrazinamide

Commence treatment

with 4 drugs

• Isoniazid


• Rifampicin


• Pyrazinamide


• Ethambutol
  (or streptomycin)

Check organismidentity

and sensitivities on culture

Fully

sensitive?

Continue treatment

Check compliance

Recheck sputum regularly

Continue isoniazid

and rifampicin

for 4 further months

Treat with antimycobacterial

drugs according to sensitivities

for 4 further months

Stop treatment

After 2 months of treatment

Yes

Yes

Yes

Yes

No

No

No

No

Low High

Sputum

negative?

Figure 44.2:Principles of treatment of

pulmonary tuberculosis.