416 CHAPTER 9
Ketamine
Ketamine(“Special K” or “vitamin K”) induces anesthesia and hallucinations and
can be injected or snorted. Ketamine is chemically similar to PCP but is shorter act-
ing and has less intense effects. With high doses, some users experience a sense of
dissociation so severe that they feel as if they are dying (NIDA, 2001). Ketamine use
and abuse are associated with temporary memory loss, impaired thinking, a loss of
contact with reality, violent behavior, and breathing and heart problems that are
potentially lethal (Krystal et al., 2005; White & Ryan, 1996). Regular users of ket-
amine may develop tolerance and cravings (Jansen & Darracot-Cankovic, 2001).Understanding Other Abused Substances
We fi rst consider brain systems and neural communication for each separate class of
abused substances and then look at genetics. We’ll then examine psychological and
social factors.Neurological Factors
Depending on the abused substance, different brain systems and neural communica-
tion processes are critical, as we’ll see in the following sections.Brain Systems and Neural Communication
Narcotic analgesics (heroin, in particular), hallucinogens, and dissociative anesthet-
ics have different effects on brain systems and neural communication.Narcotic Analgesics Among the narcotic analgesics, researchers have focused most of
their attention on heroin—in large part, because it poses the greatest problem.
Like other opioids, heroin slows down activity in the central nervous system.
It directly affects the part of the brain involved in breathing and coughing—the
brainstem—and thus historically was used to suppress persistent coughs. In addition,
heroin binds to opioid receptors in the brain, which has the effect of decreasing pain,
and indirectly activates the dopamine reward system (NIDA, 2000). Continued
heroin use also decreases the production of endorphins, a class of neurotransmitters
that act as natural painkillers. Opioids such as heroin bind to the same receptors as
endorphins do. Thus, heroin abuse reduces the body’s natural pain-relieving ability.
Furthermore, someone with heroin dependence has his or her endorphin production
reduced to the point that, when withdrawal symptoms arise, endorphins that would
have kicked in to reduce pain are not able to do so, making the symptoms feel even
worse than they otherwise would be. When the pain of withdrawal becomes par-
ticularly bad, the person may desperately crave more heroin in order to relieve the
pain. These symptoms also motivate those with heroin dependence to make sure
that they can get their next dose; they may steal or turn to prostitution (with its
increased risk of HIV/AIDS) to fi nance their habit.Hallucinogens THC, the active ingredient in marijuana, is chemically similar to the type
of neurotransmitters known as cannabinoids (anandamide is one such cannabinoid),On admission, the patient was observed to be agitated, with his mood fl uctuating between
anger and fear. He had slurred speech and staggered when he walked. He remained extremely
violent and disorganized for the first several days of his hospitalization, then began having
longer and longer lucid intervals, still interspersed with sudden, unpredictable periods in which
he displayed great suspiciousness, a fi erce expression, slurred speech, and clenched fi sts.
After calming down, the patient denied ever having been violent or acting in an unusual
way (“I’m a peaceable man”) and said he could not remember how he got to the hospital. He
admitted using alcohol and marijuana socially, but denied phencyclidine (PCP) use except for
once, experimentally, 3 years previously. Nevertheless, blood and urine tests were positive
for phencyclidine, and his brother believes “he gets dusted every day.”
(American Psychiatric Association, 2002, pp. 121–122)