Chapter 11
THC
Presented by Kristal Jenkins,
Sherri Notestine, & Heather Risk
THC Compared to Non-
selective Depressants
Until about 1990, marijuana was classified according
to its behavioral effects, usually as a mild sedative-
hypnotic agent, with effects similar to low doses of
alcohol and the benzodiazepines. Unlike sedatives,
however, higher doses of THC do not depress
respiration and are not lethal. Little cross-tolerance
occurs between THC and the sedative-hypnotics.
THC also produces a unique spectrum of
pharmacologic effects, including disruption in
attention mechanisms, impairment of short-term
memory, altered sensory awareness, analgesia,
altered control of motor movements and postural
control, and a possible immunosuppressive action.
THC Compared to Psychedelic
Drugs
THC does not have a similar chemical
structure to that of psychedelic drugs.
Also, much less sensory disorientation
than psychedelic drugs.
However, although infrequent, high
doses do produce hallucinations and
illusions in some users.
The Half-life of THC
The metabolism of THC itself is quite slow: an
elimination half-life of about 30 hrs. is generally
accepted, although some researchers report longer
half-life. Therefore, THC can persist in the body for
several days to about 2 weeks. Such a delay tends to
prolong and intensify the activity of subsequently
smoked marijuana, forming a type of “reverse
tolerance” to the drug, where the persistent low
levels are potentiated by subsequently smoked THC
cigarettes.
Side-effects of THC
Sedation
altered motor coordination
impaired cognition
reduced short-term memory
Smoking during pregnancy can cause
damage to the fetus.
Societal Concerns for Young
Users
Beginning use during early adolescence may lead to enduring
effects on specific attentional functions in adulthood.
Impaired ability to drive long after effects are not felt by user.
Increased high-school drop out rate
Increase in other problem behaviors
Correlated with other educational, job, and psychosocial
problems, but no causal inferences can be drawn.
Increased likelihood of some form of substance abuse or
dependence of other drugs.
Dependence Issues
Some researchers have found withdrawal symptoms
of restlessness, irritability, agitation, anxiety,
depression, reduced food intake, insomnia, nausea,
and cramping, beginning 48 hrs. after cessation of
marijuana use. However, people rarely meet the
criteria for being dependent:
1. Preoccupation with the acquisition of the drug.
2. Compulsive use of the drug.
3. Relapse to or recurrent use of the drug.
Cannabinoid Receptors
The cannabinoid receptor is a chain of 473
amino acids with seven hydrophobic domains
that extend through the cell membrane; each
region is composed of one hydrophobic
domain. When THC binds to its receptors, it
activates G-proteins that act on various
effectors including the second-messenger
enzyme adenylate cyclase and both
potassium and calcium ion channels.
Cannabinoid Receptor
Locations
The hippocampus, cerebral cortex,
cerebral cortex, cerebellum, and basal
ganglia appear to be major loci of
action of THC because these structures
are involved in cognition, learning,
memory, mood, and other higher
intellectual functions, as well as motor
functions.
Treatment
Marijuana, used alone, rarely results in
dependence. Treatments such as
psychotherapy can be appropriate for
frequent users of marijuana, but this is not
therapy for marijuana abuse; it is therapy for
an underlying psychopathology (such as
depression), one symptom of which is the use
of cannabis.
Therapeutic Uses
THC and various derivatives such as Dronabinal
(Marinol) have been used to treat nausea and
vomiting associated with chemotherapy in cancer
patients. Other potential uses of Dronabinal are to
reduce the muscle spasms and pain of multiple
sclerosis and reduce the intraocular pressure of
glaucoma. Both marijuana and non-psychoactive
synthetic cannabinoids effectively protect the brain
from permanent injury following head trauma or
stroke.
Institute of Medicine’s
Recommendations
The Institute of Medicine concluded
that cannabinoids have potential
applicability for some human
symptoms. They suggest that these
components should be delivered by a
mechanism other than inhaling smoke.
Institute of Medicine’s
Recommendations
They also recommend:
Research should continue into the
physiological effects of synthetic and plant-
derived cannabinoids and the natural function
of cannabinoids found in the body.
Clinical trials for symptom management
should be conducted.
Psychological effects of cannabinoids should
be evaluated in clinical trials.
Institute of Medicine’s
Recommendations
Studies to define the individual health risks of
smoking marijuana should be conducted.
Clinical trial of marijuana use should involve only
short-term marijuana use and be conducted where
there is reasonable expectations of efficacy and be
approved by review boards.
Short-term use of smoked marijuana should be used
when all other medications have been proven to fail,
symptoms can reasonably be expected to be relieved.