Charles,

Curiously, my original family doctor, the one who delivered me, always gave his injections in the triceps muscle rather than the deltoid which is the usual and customary practice nowadays. He did so for precisely the reasons you cite, safety and less pain, and to this day I request that my injections be given in the triceps. If you think about it, the triceps is within easy reach, is not a small muscle, can be pinched as you described, and is constantly being moved which increases blood flow to the area to speed the healing process. Also, if the length of the needle is limited to about 5/8", then the hub of the needle can be used as a "stop" to keep from going too deep yet still achieve IM penetration. If the "needle stop" technique is used as described, this in turn makes possible a very rapid injection process; and if the needle is inserted into the muscle rapidly enough so that the cutting edge of it does not stimulate the pain receptor nerve endings long enough for them to "fire," then the whole process becomes almost painless. Granted, there are some medications which specify "deep IM into a large muscle mass," and for those meds the triceps is probably an inappropriate injection site. But for small volume, dilute, aqueous parenterals the triceps has distinct advantages. I also sincerely believe that the primary reasons that the deltoid muscle is used so commonly are those of convenience, effenciency, and professional ossification.