Lithium monitoring or SE for patient education

Read this:
http://psychiatryonline.org/pb/assets/raw/sitewide/practice_guidelines/guidelines/bipolar-guide.pdf

Grain to mg or gram??

Phenobarbital comes in grains or mg, and it's VERY CONFUSING

1/4 grain = 16.2mg = 15mg
1/2 grain = 32.4mg = 30mg
1 grain = 64.8mg = 60mg
1 & 1/2 grain = 97.2mg