BUZZ-Mallinckrodt shares tumble after Citron Research tweet
** Mallinckrodt shares drop 17 pct in response to tweet from short-selling firm Citron Research
** Citron previously had targeted Valeant Pharmaceuticals ; those shares cratered after Citron report
** Citron tweet on Monday: "At these prices $MNK has signif more downside than $VRX-- far worse offender of the reimb sys - more to follow. VRX can't live in a vacuum"
** Mallinckrodt shares halted at least twice after Citron tweet
** Options active as traders snapped up near-term protection; puts trade at 12x the normal pace with 11,000 contracts traded by 2:20 p.m. ET, according to Trade Alert
** Nov 13 weekly puts at strikes ranging from $35 to $66 active; Nov $60 puts the most active contract on Monday
** Mallinckrodt shares had been off more modestly earlier on Monday, after company issued release on lupus drug missing main goal in a study
** Vanguard, Paulson & Co, Janus Capital, Viking Global among top Mallinckrodt holders, according to Thomson Reuters data (firstname.lastname@example.org; Reuters Messaging:; email@example.com)
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