The Collaborative International Dictionary of English v.0.48:

Lethargize \Leth"ar*gize\ (l[e^]th"[.a]r*j[imac]z), v. t. [imp.
   & p. p. Lethargized (-j[imac]zd); p. pr. & vb. n.
   Lethargizing (-j[imac]`z[i^]ng).]
   To make lethargic.
   [1913 Webster]

         All bitters are poison, and act by stilling, and
         depressing, and lethargizing the irritability.
                                                  --Coleridge.
   [1913 Webster]