Your Canadian I assume? We think it's 50mg morphine sulfate. Pharmascience, Canada makes other pills marked PMS, but we think the yellow ones are MS. Canadian imprints aren't in our databases, so we have to rely on user ID's.
You can type in PMS at Pharmer.org and see a couple of their pills and other ID's, and decide for yourself.
Small pale yellow pill with the imprint "PMS" 
Linear Mode
