Second edition

21.qxd 3/10/08 9:58 AM Page 660
660 Substance use disorders
Course
Recreational use of hallucinogens is very common among
adolescents and young adults; it is typically confined to
occasional use without consequences at parties or social
gatherings. Hallucinogen abuse, that is repeated use
despite significant consequences, is relatively rare. Neither
craving nor, as pointed out earlier, withdrawal occur, and
addiction is not seen.
Etiology
All of the hallucinogens exhibit complex agonist and
antagonist effects at either pre- or post-synaptic serotonin
receptors, and in the case of MDMA there may be destruction
of serotoninergic neurons (McCann et al. 1998;
Ricaurte et al. 1988).
Differential diagnosis
Mild intoxication with phencyclidine may be quite similar
to that seen with hallucinogens, but is suggested by nystagmus,
dysarthria, and ataxia.
Hallucinogen-induced flashbacks, mood changes, and
psychosis are all indicated by the preceding intoxication.
When this history is lacking, disorders noted in the differential
diagnosis for hallucinations, depression, mania, and
psychosis may be considered.
Treatment
‘Bad trips’ may be managed by supportive observation; in
some cases lorazepam may be helpful. Post-intoxication
mood changes, if severe, may require hospitalization for supportive
care until they run their course. Post-intoxication
psychosis may likewise require hospitalization and, if prolonged,
may be treated with an antipsychotic such as olanzapine.
Flashbacks generally do not require treatment but, if
frequent and troubling, consideration may be given to the
use of clonazepam in a dose of 2 mg daily (Lerner et al. 2003).
21.4 PHENCYCLIDINE AND KETAMINE
Phencyclidine and its closely related derivative ketamine are
both arylcyclohexylamines that were developed as ‘dissociative’
anesthetics. The frequent occurrence of post-operative
psychosis with phencyclidine has led to its abandonment in
medical practice; however, ketamine is still used, both as an
anesthetic and as an analgesic. Both drugs are used as intoxicants,
and the use of ketamine in this regard appears to be
on the rise. Phencyclidine is also known as PCP, ‘angel dust’,
‘hog’, and ‘peace pill’, and ketamine may be referred to as
‘K’, ‘special K’, ‘vitamin K’, ‘cat valium’, ‘kat’ or ‘kit-kat’.
Clinical features
Intoxication with phencyclidine may be roughly characterized
as mild, moderate, or severe; ketamine is less potent
than phencyclidine and only rarely produces the severe
and potentially life-threatening intoxication not uncommonly
seen with phencyclidine. Both of these drugs may be
ingested, ‘snorted’ intranasally, smoked, or injected.
Mild intoxication (Javitt and Zukin 1991; Luby et al.
1959; McCarron et al. 1981; Meyer et al. 1959; Pearlson
1981; Weiner et al. 2000) is characterized by euphoria and
a peculiar sense of detachment or dissociation. Patients
may feel as if they are floating, and their bodies may, to
them, appear misshapened. Lability, agitation, or lethargy
may appear, and behavior may become bizarre and unpredictable,
with violence in some cases. Patients may complain
of nausea, vomiting, or vertigo, and examination may
disclose dysarthria, ataxia, nystagmus (which may be rotatory,
horizontal, or vertical), myoclonus, tremor, increased
deep tendon reflexes, decreased pin-prick sensation in the
extremities, and autonomic signs, such as an elevated temperature,
tachycardia, an elevated respiratory rate, elevated
blood pressure, diaphoresis, and flushing; rather than
mydriasis, however, one typically sees miosis.
Moderate intoxication is characterized by a delirium,
which may be accompanied by delusions and visual hallucinations
(Allen and Young 1978). Abnormal movements
may appear, including facial grimacing, posturing, stereotypies,
dystonia, and opisthotonus; grand mal seizures may
also occur (Alldredge et al. 1989). Agitation may be
extreme, and in some cases rhabdomyolysis occurs, with
renal failure.
Severe intoxication is characterized by stupor or coma
(McCarron et al. 1981). In stupor, patients may be quite still
or may evidence random, purposeless movements;
myoclonus is frequent and the deep tendon reflexes are
greatly increased. With even higher doses coma supervenes;
this is a kind of ‘coma vigil’ in which the eyes are open and
the patient appears vigilant, but shows no response to pain
or to anything else. The temperature rises further, as does
the blood pressure, and in some cases a hypertensive
encephalopathy occurs. The electroencephalogram (EEG)
in these cases shows profound generalized slowing.
The duration of intoxication with ketamine, which has
a half-life of about 3 hours, is approximately 4–6 hours.
Phencyclidine intoxication is longer for two reasons. First,
the half-life of phencyclidine is longer, anywhere from 7 to
20 hours. Second, phencyclidine is a weak base and hence
is ‘trapped’ in the stomach; phencyclidine is also lipophilic
and is therefore taken up into adipocytes. Thus protected
from hepatic metabolism, phencyclidine may linger for
prolonged periods, and indeed may be detectable in the
blood for weeks or longer after a single dose. Overall,
intoxication with phencyclidine tends to last from half a
day up to many days and, during the overall resolution of
phencyclidine intoxication, the clinical picture may fluctuate
fairly widely.