Douglas Harper's Etymology Dictionary
Wiktionary
intramuscular
a. Inside a muscle or the muscles.
WordNet
intramuscular
adj. within a muscle; "an intramuscular injection"
Wikipedia
Usage examples of "intramuscular".
The cramps in her muscles grew steadily more frequent and more intense, but it wasn't intramuscular pain that made the hours between eleven and three so terrible.
Lynn guessed she'd been given an intramuscular injection of some sort of tranquilizer, and it probably hadn't worn off all the way yet.
Lee replied and used a cotton swab to sterilize his patient's upper arm before giving her the intramuscular injection of birth control that would work for three months before she needed another shot.