Sudden Hearing Loss in my Dog

Question
2 weeks ago I brought my 90lbs -10 year old lab to the vet for an ear infection.  She was prescribed a series of medications from Otomax ear drops 2X daily for 7 days, 500mg 2X daily of Cephalexin and 30mg of Predisone for a series of days.  I only administered the ear drops for about  4 days and continued on with the other medication as prescribed.  2 days ago I noticed that my lab could no longer hear properly and immediately brought her back to the vet. He checked her eardrum and said the infection was gone but there was fluid in one of her ears, but other than that her eardrums were perfectly intact.  He also performed a test by dropping a metal bowl behind her, which she did not respond to. Is it possible that the combination of medications caused her sudden ear loss? Is it possible for any of her hearing to return?  I'm concerned that since both ears were affected that it was caused by the medication.  Prior to me bringing her in 2 weeks ago she had perfect hearing.

Answer
There is a very small percentage of dogs who have a sensitivity to the Gentamicin that is in Otomax.  This can lead to hearing problems, which can in many cases be reversible.  Was the Otomax administered in both ears or only one?  Discontinuing it is the best solution and hopefully problem from it would resolve if this in indeed the case with her.

My sincere apologies for the delay.  A family emergency kept me away for a time.