The Collaborative International Dictionary of English v.0.48:

Lenitive \Len"i*tive\ (-t[i^]v), a. [Cf. F. l['e]nitif. See
   Lenient.]
   Having the quality of softening or mitigating, as pain or
   acrimony; assuasive; emollient.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lenitive \Len"i*tive\, n. [Cf. F. l['e]nitif.]
   1. (Med.)
      (a) A medicine or application that has the quality of
          easing pain or protecting from the action of
          irritants.
      (b) A mild purgative; a laxative.
          [1913 Webster]

   2. That which softens or mitigates; that which tends to allay
      passion, excitement, or pain; a palliative.
      [1913 Webster]

            There is one sweet lenitive at least for evils,
            which Nature holds out; so I took it kindly at her
            hands, and fell asleep.               --Sterne.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lenitive
    adj 1: moderating pain or sorrow by making it easier to bear
           [syn: alleviative, alleviatory, lenitive,
           mitigative, mitigatory, palliative]
    n 1: remedy that eases pain and discomfort