Velocity serums

Velocity 9 is a drug that allows temporary access to the Speed Force. Initially developed by Dr. Harrison Wells as Velocity 6, the current version of the drug was created by Dr. Caitlin Snow. Despite its benefits, this drug is also very dangerous, as it causes cellular degeneration and eventually death.

History
Wells first started to develop a speed-enhancing drug after Zoom appeared on his Earth, and it was meant to aid Jay Garrick in his struggles against the super-villain. However, his first five attempts (Velocity 1 to 5) were failures. A version of the drug, created by "Jay", caused the loss of "Jay"'s powers and his cellular degenerative disease.

The drug was first mentioned by Wells after he had traveled to Earth One and joined Team Flash. He explained its history to Caitlin Snow. She helped him create a successful version of the drug with her expertise in biochemistry. They produced the sixth (and the first successful) version of the drug by adding sodium chlorate, as the drug needed an extra release of oxygen to function.

Though initially reluctant to use the Velocity 6, "Jay" took the drug in order to restore his connection to the Speed Force and save Wells after he had been shot by Patty Spivot. When Wells later thanked "Jay" for saving his life, Jay however told him to keep the drug away from Barry.

When Barry had traveled to Earth-Two, Central City was attacked by Geomancer, and "Jay Garrick" had to take Velocity 7 to stop him. Due to V7's short-lived effects, Caitlin made Velocity 8, but was forced to immediately create Velocity 9 due to the problems with Velocity 8. Velocity 9 was the first version of the compound to seemingly cause no side-effects, and it also triggered "Jay"'s latent regenerative abilities. Velocity 9 lasted long enough for Jay to save the day.

During Velocity 9's development, Caitlin had asked Eliza Harmon for help, as she was having trouble with the synthesis. She sent information on 3 of the 8 components to Eliza. Eliza reverse engineered the drug, and used it to gain super-speed. The drug caused Eliza to develop an immoral split personality which became Trajectory. At Star Labs, Trajectory held Caitlin, Cisco, Harrison & Jesse hostage in order to obtain more Velocity 9. She injected Jesse Quick with Velocity 9 when she grew impatient, and Dr. Wells saved her life by undergoing a blood transfusion.

Before Trajectory disappeared (possibly due to the accelerated cellular degeneration), her lightning turned blue. This, coupled with knowledge about "Jay"'s illness, led the team to deduce that Zoom had taken the Velocity drug and was dying.

Characteristics
The drug temporarily increases the user's speed beyond normal limits, and this speed far exceeds the speed of the Flash at Mach 2.2. However, the drug has several side-effects. A highly addictive drug, it causes rapid cellular degeneration. In one case, the user developed a psychotic second personality that caused her to commit criminal acts. At some point, the drug causes the lightning generated by a speedster to turn from the usual gold into blue.

Certain versions of the drug had more problems. "Jay Garrick's" version of Velocity 6 caused him to lose his connection to the Speed Force, and the cellular degeneration he had suffered was slowly killing him. Velocity 7 granted super-speed for too short a time. Velocity 8 had numerous kinks which led to the immediate development of Velocity 9. While Velocity 9 initially seemed to cure the damage caused by previous versions, it was revealed that this was not true.

It is unclear if Eliza's cellular degeneration was accelerated due to her lack of caution in using Velocity 9 repeatedly, or due to her lack of a natural connection to the Speed Force prior to using the drug.

Known users

 * Hunter Zolomon/Zoom
 * Eliza Harmon/Trajectory (deceased)
 * Jesse Quick (unwillingly; formerly)

Behind the scenes

 * In the DC comics, Velocity 9 was a drug created by Vandal Savage that granted a temporary speed enhancement. It was sold in the illegal drug trade. It too had severe side-effects.
 * Another variation called Speed Juice exists in the mainstream comics as well. This variation is the power source of the Flash's Crime Syndicate counterpart, Johnny Quick