(Adds Mallinckrodt response; updates shares)
Nov 10 (Reuters) - Influential short-seller Citron Research's Andrew Left, who accused Mallinckrodt Plc of being an offender of the reimbursement system, told CNBC on Tuesday that he has a short position on the company's stock.
Mallinckrodt's stock plunged 26 percent on Monday after Left's tweet on the drugmaker.
However, the stock recovered on Tuesday and were up 8.11 percent at $62.71 in late afternoon trading as Left did not lay out specific accusations against the company.
Left, in the interview to CNBC, accused Mallinckrodt's Chief Executive Mark Trudeau of misrepresenting the efficacy of the drugmaker's biggest product, Acthar.
Acthar, which has been in the U.S. market for the past 65 years, accounted for about 28 percent of Mallinckrodt's latest quarterly revenue of $965.1 million.
Mallinckrodt gained rights to Acthar Gel through its acquisition of Questcor Pharmaceuticals Inc for about $5.6 billion in 2014.
Trudeau called the short-seller's accusations "completely false" in an interview with CNBC.
Citron published a scathing report on Valeant Pharmaceuticals International Inc late October, accusing the Canadian drugmaker of using specialty pharmacies to inflate revenue. Shares plunged 40 percent on the day.
"My short on Valeant has been significantly scaled down from where it was earlier," Left told CNBC on Tuesday. (Reporting by Ankur Banerjee in Bengaluru; Editing by Anil D'Silva and Sriraj Kalluvila)