The clinical management of the drug-resistant patient.
The specific management of drug-resistant patients is only possible where facilities exist for both mycobacterial culture and for drug-susceptibility testing. Treatment guidelines in the United Kingdom and elsewhere are predicated on the drug-resistance data prevailing in the circumstances of their use. In developed countries, the inclusion of the fourth drug (ethambutol but occasionally streptomycin) depends on the level of isoniazid resistance expected or known in a given patient group. Most parts of the world do not have the capabilities to perform mycobacterial culture and drug-susceptibility testing. In these countries, therefore, the "standard" advised regimen has to cover the possibility of the commoner drug resistances. The view taken in the United Kingdom is that where drug-susceptibility tests are available, they should be followed, and treatment modified. The drug treatment of multidrug-resistant tuberculosis (MDR TB), defined as combined resistance to rifampicin and isoniazid, plus or minus other antituberculosis drugs, is complex, time consuming, and demanding on both patient and physician. In the United Kingdom the advice is that treatment should only be carried out by physicians with substantial experience in managing complex resistant cases, only in hospitals with appropriate isolation facilities, and in very close liaison with Mycobacteriology Reference Centres. Treatment should start with five or more drugs to which the organism is, or is likely to be, susceptible and continued until sputum cultures become negative. Treatment with three drugs should continue for at least an additional nine months.