If we pursue the logic of the "cascade of regimens" and consider the drug resistance is a stepwise introduction following the introduction of the drugs into chemotherapy, we can display the above sequence of regimens.
Fully drugs susceptible tuberculosis could be treated with 90% effectiveness with the 18-month regimen introduced in Edinburgh in the 1950s (see earlier slide). The 8-month regimen based achieved a similar effectiveness (slightly less in fact with about 2% "failures" and around 10 to 15% "relapses", depending a bit on the setting and the quality of ascertainment).
Patients failing or relapsing could be successfully treated with a rifampicin-thoughout regimen of six or commonly of eight months duration.
With the above, there were two steps possible. The first step has now been largely abandoned but an effective fallback regimen for failures and ralapses is still required and it must be available in the same jurisdiction as the first-line regimen, ie in a place near the residence of the patient requiring it. Centralizing such treatment in one or a few centers in a country will not be a viable option for a truly "national program".
As dicussed in an earlier slide, a very small proportion of patients with multidrug-resistant tuberculosis in low-income countries has currently access to appropriate chemotherapy, for various reasons. A key issue for a regimen is to be not only concerned about the putative efficacy of the drugs that make up the regimens (there has not yet been a single clinical trial for multidrug-resistant tuberculosis, recommended regimens are base on expert opinion), but to utilize a regimen that will be completed by the largest possible propoertion of patients for whom it is prescribed.
We list above the "Bangladesh-type" regimen which shall be discussed shortly which may satisfy the conditions of affordability, tolerance, and possibility to move it to the intermediate level or perhaps even further into the periphery. |
