Merriam-Webster's Collegiate® Dictionary, 11th Edition
DOSE
I. noun see: date
Date: 15th century
1. the measured quantity of a therapeutic agent to be taken at one time, the quantity of radiation administered or absorbed, a portion of a substance added during a process, an amount of something likened to a prescribed or measured quantity of medicine , a gonorrheal infection,
II. transitive verb (dosed; dosing)
Date: 1654
to give a dose to, to divide (as a medicine) into doses, to treat with an application or agent