The rush is far less pronounced with IM and a 'warm blanket' effect might be much harder to attain, depending on tolerance.
[TABLE="class: grid, width: 500, align: center"]
[TR]
[TD]ROUTE[/TD]
[TD]ONSET [/TD]
[TD] PEAK[/TD]
[TD] DURATION[/TD]
[/TR]
[TR]
[TD]PO
[/TD]
[TD]unknown [/TD]
[TD] 60 min[/TD]
[TD]4-5 hr[/TD]
[/TR]
[TR]
[TD]PO-ER[/TD]
[TD] unknown[/TD]
[TD] 3-4 hr[/TD]
[TD]8-24 hr[/TD]
[/TR]
[TR]
[TD]
IM[/TD]
[TD]
10-30 min[/TD]
[TD]
30-60 min[/TD]
[TD]4-5 hr[/TD]
[/TR]
[TR]
[TD]
IV[/TD]
[TD]
Rapid[/TD]
[TD]
20 min [/TD]
[TD]4-5 hr[/TD]
[/TR]
[TR]
[TD]Rectal [/TD]
[TD]unknown[/TD]
[TD]20-60 min[/TD]
[TD] 3-7 hr[/TD]
[/TR]
[TR]
[TD]Subcutaneous[/TD]
[TD] 20 min[/TD]
[TD] 50-90 min[/TD]
[TD] 4-5 hr[/TD]
[/TR]
[TR]
[TD]Epidural[/TD]
[TD]6-30 min[/TD]
[TD]1 hr [/TD]
[TD]up to 24 hr[/TD]
[/TR]
[TR]
[TD]I.Thecal[/TD]
[TD]rapid (min)[/TD]
[TD] unknown [/TD]
[TD] up to 24 hr[/TD]
[/TR]
[/TABLE]
Also rotating is important as MS can cause irritation, redness and swelling at the IM site.
Opioid-induced histamine release may be responsible for uriticaria & wheals.
( ^ this always happens to me if I end up getting some in subcutaneously)