Shares in Indivior, maker of the opioid addiction treatment Suboxone, jumped by 23% 54.48p after it lifted its outlook for the full-year.
It now expects to make a annual profit of between $80m (£63.8m) to $130m, after a better than expected performance of Suboxone.
Indivior had previously forecast a loss of $40m to a profit of $10m.
The company also expects annual revenues of between $670m (£534.6m) and $720m. It compares to previous forecasts of between $525m and $575m.
Indivior said Suboxone had performed better than expected.
Indivior was previously part of Reckitt Benckiser which today said it had paid $1.4bn to settle claims in the US over the sales and marketing of Suboxone.