Jan 15 (Reuters) - Indivior Plc revised its annual revenue forecast higher than earlier on Friday, encouraged by a recovery in U.S. sales of the British drugmaker's opioid addiction treatment in the fourth quarter, sending its shares up by 7.4% in early trade.

The company's Suboxone film, whose cheaper copycat versions have hurt Indivior's sales in the past, has been one of the main treatments for addiction through a growing epidemic of opioid abuse in the United States.

It added that it expected to deliver adjusted pre-tax income ahead of its expectations.

Indivior had said in October that it saw modest improvement in new patient enrollments in the third-quarter, compared to a rapid decline in the prior quarter, due to coronavirus-related disruptions.

Indivior has been embroiled in multiple legal battles over the past years, including a 1.07 billion pound ($1.46 billion) legal claim from former parent Reckitt Benckiser relating to their demerger agreement. It last year agreed to pay $600 million to settle U.S. opioid treatment marketing claims.

The drugmaker said it expected annual revenue to be in the range of $645 million to $650 million, up from its previous guidance range of $595 million to $620 million. In 2019, it reported an annual revenue of $785 million.

Shares of the FTSE-250 drugmaker, which nearly tripled in value last year, was the top percentage gainer on the index after the announcement. ($1 = 0.7321 pounds) (Reporting by Indranil Sarkar in Bengaluru; Editing by Saumyadeb Chakrabarty and Rashmi Aich)