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The Toxicity of Recreational Drugs

Alcohol is more lethal than many other commonly abused substances

Robert Gable

Safety Comparison

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.

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