Rechallenge if ALT levels <2× ULN, bilirubin normal and symptoms abated Start simultaneously with EMB and RIF, INH and PZA at usual doses, every 2–3 days Repeat LFT measurements before reintroducing a new drug If symptoms recur or ALT increases, the last drug reintroduced should be withdrawn Reintroduce full treatment over a period of up to 21 days† If RIF, EMB and INH were reintroduced without further increases in transaminases, PZA can be suspended, in which case TB treatment should be extended to 9 months (continuation phase extended from 4 to 7 months). This evidence concerns the gene GPT and tuberculosis.