Interventions for Tuberculosis Control and Elimination 2002

evidence was the trial of the International Union Against Tuberculosis
Committee on Prophylaxis (figure 83). 123 Among “completer-compliers”
the answer is quite clear-cut. Most benefit was obtained with twelve months
chemotherapy with 93% protection, while six months offered 69% protection,
and three months 32%.
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Figure 83. Impact of duration of intake of isoniazid preventive therapy on protective
efficacy. 123
However, if all patients were analyzed (and not only “completer-compliers”),
the differences between six months and twelve months became
much smaller, as adherence dropped with increasing length of treatment.
For this reason and considering the cumulative risk of adverse drug events
and personnel costs, it has been suggested that six months of preventive
chemotherapy with isoniazid was more cost-effective than twelve
months. 895
However, the primary decision that has to be taken in the selection
of a regimen (curative or preventive) is efficacy; the second is effectiveness.
In consideration of these findings, recommendations have been made
for preventive chemotherapy to be given for six to twelve months, with
every effort made to ensure adherence for six months. 356 The isoniazid
preventive chemotherapy trials in the United States showed that the optimum
duration might lie somewhere around nine months (figure 84). 896 The
American Thoracic Society and the US Centers for Disease Control now
recommend nine months of isoniazid treatment. 897 The British Thoracic
Society recommends six to twelve months for preventive chemotherapy, the
longer duration recommended for HIV-positive patients. 898,899
137