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Special K: ketamine, a noncompetitive N-methyl-D-aspartate (NMDA) glutamate receptor antagonist.

From a number of PubMed abstracts:
In numerous studies ketamine is described as a safe sedative agent for children undergoing painful procedures. Ketamine rapidly induces a dissociative state with profound analgesia and amnesia for the event while preserving airway reflexes and ventilation. The greatest experience with ketamine as an anaesthetic agent is in the developing world where it is frequently used by non-anaesthetists in situations where monitoring equipment is poor or absent.

The excellent safety profile of ketamine has made it the drug of choice for both pediatric sedation and much veterinary medicine. Fortunately, this safety record also means that few patients who deliberately overdose during recreational use will have substantial morbidity or mortality. Most morbidity and mortality will occur from accidents during the induced dysphoric state. Since vomiting occurs with high doses, aspiration is a distinct possibility in the deeply comatose patient.