I saw this TV series that had a criminal whose brother is in a government agency (I am not certain about the brother part) to save him from the prison. He is recruited, and he is experimented on to become the super spy. But to stop the criminal from running away, there is a fail-safe that requires the consumption of some sort of medication to null the side effects of being invisible. I thought its name was Rake, but when I searched for Rake, it turned out to be something else. Can anyone please tell me the name of this TV series?
Sounds alot like the 2000 Sci-fi Channel TV series The Invisible Man. Wikipedia's summary touches on the key similarities:
The plot revolves around Darien Fawkes (Ventresca), a thief facing life imprisonment who was recruited by a low-rent spy organization and given the power of invisibility via implantation of a special "Quicksilver gland" in his head. The gland allows Fawkes to secrete a light-bending substance called "Quicksilver" from his pores and follicles. The substance quickly coats his skin, hair, nails and clothes and renders him invisible. He can consciously release the Quicksilver, which then flakes off and disintegrates. However, the Quicksilver gland was sabotaged at its creation by scientist Arnaud DeFehrn to release a neurotoxin that accumulates in the bloodstream and causes intense pain, followed by antisocial behavior and psychosis. The host requires regular doses of "counteragent" to keep him sane and healthy, which is controlled by said government agency.
The bolding is mine, to highlight the elements that match your description.