The Toxicity of Recreational Drugs
Alcohol is more lethal than many other commonly abused substances
Despite these difficulties, it is evident that there are striking
differences among psychoactive substances with respect to the
lethality of a given quantity. The way a substance is absorbed is
also a critical factor. The common routes of consumption, from
the least toxic to the most toxic (in general), are: eating or
drinking a substance, depositing it inside the nostril, breathing or
smoking it, and injecting it into a vein with a hypodermic syringe.
So, for example, smoking methamphetamine (as is done with the
increasingly popular illicit drug "crystal meth") is more
dangerous than ingesting it.
Once a drug enters the body, physiological reactions are determined
by many factors, such as absorption into various tissues and the
rates of elimination and metabolism. Individuals vary enormously in
how they metabolize different substances. One person's sedative can
be another person's poison. This variability alone introduces
unavoidable ambiguities in estimating effective and lethal doses.
Still, the wide range between different substances suggests that
they can be rank-ordered with reasonable confidence. One can be
quite certain, for example, that the risk of death from ingesting
psilocybin mushrooms is less than from injecting heroin.
The most toxic recreational drugs, such as GHB
(gamma-hydroxybutyrate) and heroin, have a lethal dose less than 10
times their typical effective dose. The largest cluster of
substances has a lethal dose that is 10 to 20 times the effective
dose: These include cocaine, MDMA (methylenedioxymethamphetamine,
often called "ecstasy") and alcohol. A less toxic group of
substances, requiring 20 to 80 times the effective dose to cause
death, include Rohypnol (flunitrazepam or "roofies") and
mescaline (peyote cactus). The least physiologically toxic
substances, those requiring 100 to 1,000 times the effective dose to
cause death, include psilocybin mushrooms and marijuana, when
ingested. I've found no published cases in the English language that
document deaths from smoked marijuana, so the actual lethal
dose is a mystery. My surmise is that smoking marijuana is more
risky than eating it but still safer than getting drunk.
Alcohol thus ranks at the dangerous end of the toxicity spectrum. So
despite the fact that about 75 percent of all adults in the United
States enjoy an occasional drink, it must be remembered that alcohol
is quite toxic. Indeed, if alcohol were a newly formulated beverage,
its high toxicity and addiction potential would surely prevent it
from being marketed as a food or drug. This conclusion runs counter
to the common view that one's own use of alcohol is harmless. That
mistaken impression arises for several reasons.
First, the more frequently we experience an event without a negative
outcome, the lower our level of perceived danger. For example, most
of us have not had a life-threatening traffic accident; thus, we
feel safer in a car than in an airplane, although we are 10 to 15
times more likely to die in an automobile accident than in a plane
crash. Similarly, most of us have not had a life-threatening
experience with alcohol, yet statistics show that every year about
300 people die in the United States from an alcohol overdose, and
for at least twice that number of overdose deaths, alcohol is
considered a contributing cause.
Second, having a sense of control over a risky situation reduces
fear. People drinking alcoholic beverages believe that they have
reasonably good control of the quantity they intend to consume.
Control of the dose of alcohol is indeed easier than with many
natural or illicit substances where the active ingredients are not
commercially standardized. Furthermore, alcohol is often consumed in
a beverage that dilutes the alcohol to a known degree.
Consider the following: The stomach capacity of an average adult is
about 1 liter; therefore, a person is unlikely to overdose after
drinking beer containing 5 percent alcohol. Compare this situation
to GHB (a depressant originally marketed in health food stores as a
sleep aid), where stomach capacity does not place much of a limit on
consumption because the effective dose is only one or two
teaspoonfuls. No wonder that more than 50 percent of novice users of
GHB have experienced an overdose that included involuntary loss of consciousness.
Another reason that alcohol is often thought to be safe is that
popular media do not routinely report fatalities from alcohol
overdoses. Deaths are usually considered newsworthy when they
involve a degree of novelty. Thus a fatality caused by LSD or MDMA
is thought to be more interesting than one caused by alcohol.