intravenous

adj. occurring within a vein or veins, entering through a vein

Intravenous therapy or IV therapy is the giving of liquid substances directly into a vein. It can be intermittent or continuous; continuous administration is called an intravenous drip. The word intravenous simply means "within a vein", but is most commonly used to refer to IV therapy. Therapies administered intravenously are often called specialty pharmaceuticals.
See more at Wikipedia.org...

Adjective
1. within or by means of a vein; "an intravenous inflammation"; "intravenous feeding"
(synonym) endovenous
(pertainym) vein, vena, venous blood vessel

(a.)
Within the veins.
  

Injected into a vein. Also called IV.