Real Madrid have confirmed that Michael Essien has been unavailable for recent matches after having an allergic reaction to medicine he was given by the club.
The Ghanaian midfielder is on loan at the Spanish champions from Chelsea and put in some impressive performances in the opening weeks of the campaign.
However, Essien has not played since November 11 and Real had previously kept quiet about the reasons for his absence until assistant coach Aitor Karanka explained the situation.
"He has had an allergic reaction to some medicine," Jose Mourinho's right-hand man told reporters.
Karanka also confirmed that Real are not currently putting a timescale on when Marcelo and Gonzalo Higuain will return from a broken foot and thigh injury respectively.
"Marcelo's injury is a long one and it depends on how things evolve," he added. "Today or tomorrow he will come out of the cast.
"Gonzalo's injury is muscular. We have to be careful and judge the best time for him to return."
Cobblers boss Aidy Boothroyd said: "We have been looking to get Lewis out on loan so we can get him some football.
"I think he's been really unfortunate in that because of the injuries we've had he's played in every position apart from his own.
"When he did play up front last season he scored and he's at a stage now where he needs to get some games in."
