"Don't worry, Hank—you're amped up enough."
Turk is a recreational drug used by terrans, one that is detrimental in excessive doses and/or over an extended period of time. Applied via an arm patch, it appears to produce a similar feeling to the drug hab, being able to act as a short term substitute in the absence of its counterpart. It is not as potent however.
Turk makes a user feel more aware of their surroundings, to the point of distraction.
When a subject is overdosed, it causes hallucinations and severe health problems.