A violent young woman requiring four paramedics to subdue her is MOST likely under the influence of:

The correct answer is PCP (phencyclidine). PCP is a dissociative anesthetic that can produce severe psychological effects, including agitation, hallucinations, and aggressive behavior. A person under the influence of PCP may exhibit extreme strength and resistance to pain, making them difficult to manage, which aligns with the scenario where a violent young woman needs four paramedics to subdue her.

In contrast, while mescaline and LSD are hallucinogens that can induce altered states of consciousness and visual or auditory hallucinations, they do not typically result in the same level of physical aggression or strength as seen with PCP. Ketamine, also a dissociative anesthetic, might produce similar effects to PCP but usually does not lead to the same level of agitation or violent behavior. This distinction in the nature and intensity of the effects is important in understanding why PCP is the most likely substance influencing the described behavior.