212 Ketamine
were euphoric; some screamed in apparent terror. A study found such effects
to be twice as common in female patients as in males. Such effects are stronger
among alcohol abusers. The floating sensation may occur as people regain
consciousness before they regain sense of touch, a sequence that would tem-
porarily eliminate awareness of gravity. One surgery patient experienced LSD-
like effects that continued even after release from the hospital. Reports exist
of patients experiencing psychological effects for a year after a dose. A re-
viewer who examined many years of scientific reports about ketamine, how-
ever, found a consensus that long-term psychological consequences from
ketamine occur no more frequently than with other anesthetics—a conclusion
about incidental effects from anesthetic use, not about deliberate effects in-
duced as part of psychotherapy or illicit use.
One authority claims that the greatest physical hazard has a psychological
base, as users sometimes become indifferent about death and take risks they
would otherwise avoid. Persons intoxicated with ketamine may be woozy and
have lower perception of pain, conditions that can cause or worsen accidents.
Female lemmings are more susceptible to the drug than males. While the
male-female difference does not necessarily carry over to humans, use of ke-
tamine’s anesthetic properties by sexual predators seeking to weaken victims
was publicized in the 1990s. Researchers using the drug to treat alcoholism
have found that ketamine makes a person more susceptible to suggestions,
perhaps making a person more vulnerable to manipulation.
Abuse factors.Tolerance and dependence can develop when rats and mice
receive ketamine. Those traditional signs of addictive potential seem uncon-
firmed in human use, but people have been known to take the drug daily for
no medical purpose and to feel they have a problem with that usage.
Drug interactions.In surgery patients administeringdiazepamsimultane-
ously with ketamine has diminished unwanted psychological effects such as
delirium and nightmares.Midazolammay also help.
In experimentation with rats and mice the actions of ketamine and alcohol
have similarities, and the two have cross-tolerance (meaning one can substi-
tute for the other in various ways). Human alcoholics report that ketamine
produces sensations like those of alcohol. A small study found that ketamine
has stronger effects on perceptions and thinking skills in alcoholics than in
other persons.
In ratsmorphinecan boost some pain relief from ketamine, and ketamine
can reduce pain relief from morphine. In contrast, a human experiment found
that patients needed less morphine for pain relief if they also received keta-
mine. In humans ketamine can boost opiate and barbiturate actions so much
as to be fatal.Lorazepam can boost the sedative and amnesia qualities of
ketamine in humans.
Cancer.Not enough scientific information to report.
Pregnancy.Experimentation on mice shows that birth defects can occur
when ketamine andcocaineare used together, but the impact of just ketamine
seems uncertain. Experiments on pregnant rats, rabbits, and dogs have pro-
duced no harm. Ketamine has harmed hamster genes when they are experi-
mented upon outside the body. Research published as the twenty-first century
began indicated that the drug may harm fetal brain development in humans.