Dargol
From The Stargate Omnipedia
Experimental substance developed by Linea in her attempts to create a Fountain of Youth. She hoped to eventually use this chemical on herself, but first tested it on two Vyan test subjects.
Not realizing the scope of her project, the Dargol wiped out the entire infant population of Vyus and regressed the older individuals into much younger people, wiping them of their memories. Linea herself was exposed to the substance.
Some time later Dr. Janet Fraiser, along with the young Ke'ra (Linea), concocted an antidote for the Dargol to restore the memories of the people of Vyus.
KEY EPISODE
Past and Present - SG-1 encounters a world where the population has succumbed to an anti-aging substance called Dargol, and have had their memories entirely wiped.