What pill is white and round and has a M with a square around it imprinted on the pill?

Not Medical Advice: METHYLIN Methylphenidate HCl Tablets, 20 mg Methylphenidate is a central nervous system stimulant.
Answered by kgb agent Siegfred C on Wednesday, September 12 2012 at 04:23PM EDT
Source: www.drugs.com/...