The Onpharma Company. The Onpharma Company has unveiled the Onset EZ buffering pen. The pen buffers individual cartridges of local anesthetic to adjust their pH to a more neutral pH before use, Onpharma said. Each pen contains a sterile solution of 8.4% sodium bicarbonate and water and is sufficient to buffer 30 local anesthetic cartridges. The pen can be used up to 30 days after being opened.