Rc suppressants (Rc抑制液, Rc yokuseieki) are the drugs used to suppress the activity of the kakuhou. They were specially made by the CCG's Medical Department, designed for the sole purpose of inhibiting the activity of a ghoul's Rc cells. However, they can also be applied on humans as well since it is the only known treatment for Rc cell over-secretion disease (ROS). While available to the general public for this purpose, their cost makes them nearly impossible for most to afford. However, it is only made available for distribution by special affiliates of and from the CCG.
Mostly seen in fluid form, in a solid light color. They are usually stored in tubular containers, in an airtight and sterile environment. In a liquid state, Rc suppressants carry an odor. To a ghoul, it is described as a unforgettable pungent odor that fills the nostrils.
Injected in fluid form, Rc suppressants are delivered via a hypodermic needle into the muscle. This can be managed by one of two known methods, a syringe or a dart. Upon injection, the drug is absorbed fairly quickly, a trait usually attributed to unknown chemicals the drug itself is manufactured with; of which ingredients include an Rc solution for Rc suppressants. Injected drugs are usually preferred as they allow the full effects of the drug to be experienced, but it is yet to be seen if Rc suppressants can be administered by other means.
The effects to ghouls include slower regeneration, kagune impairment, and vulnerability to mundane items such as knives; grogginess has been observed but it is unconfirmed to be either an intended symptom or a common side effect. When Rc cell activity is suppressed, it may cause an increase in melanin, most specifically black eumelanin, which, if too abundant, causes grey or white hair. When Rc suppression is not extreme, the body is allowed to create brown eumelanin that allows the black and brown eumelanin to balance and the hair will be black. It does eventually wear off, but the specific time before this occurs is unknown as well.
The CCG uses Rc suppressants as a means to subdue a ghoul rather than to exterminate. Cochlea uses it for their ghoul prisoners, to weaken them for interrogation and/or as a measure for caution. Another known use which takes advantage of the ghoul's newfound vulnerability is for surgery or dissection.