''I felt I had influenced her.'' Mariann Caprino, a spokeswoman for Pfizer, said: ''These allegations are six years old. The actions that allegedly occurred took place well before Pfizer completed its merger with Warner-Lambert. It is firm and established Pfizer policy not to allow our sales representatives to make inappropriate claims or encourage off-label use of any of our medicines.'' The lawsuit, brought by Dr. David P. Franklin, a former Warner-Lambert employee, is based on thousands of pages of internal company documents. The documents do not reveal whether doctors told their patients who the third person was in the examining room. Dr. Franklin accuses Warner-Lambert's sales representatives of encouraging doctors to experiment by prescribing Neurontin for unapproved uses including pain, bipolar disorder and attention deficit disorder in children.