From the TSA website, though I saw them ignore this over last weekend with somebody and a 4 oz tube of KY (probably because the old woman barely spoke english and didn't challenge them):

To ensure the health and welfare of certain air travelers there are no limits on the amounts of the following liquids, gels and aerosols you may carry through a security checkpoint:

Baby formula and breast milk if a baby or small child is traveling;
All prescription and over-the-counter medications (liquids, gels, and aerosols) including KY jelly, eye drops, and saline solution for medical purposes;

from http://www.tsa.gov/press/happenings/..._guidance.shtm