The Collaborative International Dictionary of English v.0.48:

Alterative \Al"ter*a*tive\, n.
   A medicine or treatment which gradually induces a change, and
   restores healthy functions without sensible evacuations.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Alterative \Al"ter*a*tive\, a. [L. alterativus: cf. F.
   alt['e]ratif.]
   Causing ateration. Specifically: Gradually changing, or
   tending to change, a morbid state of the functions into one
   of health. --Burton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

alterative
    adj 1: tending to cure or restore to health; "curative powers of
           herbal remedies"; "her gentle healing hand"; "remedial
           surgery"; "a sanative environment of mountains and fresh
           air"; "a therapeutic agent"; "therapeutic diets" [syn:
           curative, healing(p), alterative, remedial,
           sanative, therapeutic]