** Canadian drugmaker Valeant Pharmaceuticals International Inc's U.S.-listed shares down 0.9 pct at $84.49 after falling as much as 7.4 pct earlier; Mallinckrodt Plc up 8 pct at $62.12
** Influential short seller Citron Research's Andrew Left told CNBC on Tuesday that he has been short on Mallinckrodt on and off for nearly four years
** Mallinckrodt's stock plunged 26 pct on Monday after Citron turned the spotlight on the company after it tweeted that the drugmaker was "a far worse offender of the reimbursement system"
** Left also said his short on Valeant has been significantly scaled down from where it was earlier
** Valeant CEO said on Tuesday on a conference call that cutting ties with a controversial specialty pharmacy will hurt the dermatology business of Valeant in the short term
** Valeant YTD share performance : link.reuters.com/rup85w
** Up to Monday's close, Valeant's shares had fallen about 45 pct since Citron published report on Oct. 21 accusing Valeant using specialty pharmacies to inflate revenue