How does alcohol affect cocaine toxicity?

Updated: Sep 01, 2018
  • Author: Lynn Barkley Burnett, MD, EdD, LLB(c); Chief Editor: Sage W Wiener, MD  more...
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More than 38 pharmacologically active substances have reportedly been used with cocaine; alcohol and nicotine are the most common. Although alcohol and nicotine are individually well known for their potential sequelae, their use with cocaine may acutely increase morbidity and mortality risks.

Between 30% and 60% of individuals who take cocaine combine it with alcohol. Clinical data indicate that the concurrent use of alcohol and cocaine is associated with increased mortality and morbidity from cardiovascular complications, hepatotoxicity, and behaviors leading to personal injury. In 74% of cocaine-related fatalities in the United States, another drug, usually ethanol, had been co-ingested. The addition of alcohol to cocaine increases the risk of sudden death 25-fold.

The increased risk from the concomitant alcohol use is enhanced by the formation of a third active compound of toxicologic importance, namely, ethylbenzoylecgonine, commonly known as cocaethylene. Although its behavioral pharmacology and psychomotor stimulant effects are similar to those of cocaine, its toxicity is greater. The plasma half-life of cocaethylene is longer than that of cocaine, and inferential evidence suggests that the lethal dose to kill 50% of subjects (LD50) is lower.

Although most cocaine metabolism involves serum cholinesterase, some of the drug is metabolized in the liver by carboxylesterases. In the presence of alcohol, a nonspecific carboxylesterase catalyzes ethyl transesterification of cocaine to cocaethylene. Cocaine is the rate-limiting substrate in this reaction. Cocaethylene can be detected in urine and blood within 100 minutes after a person uses alcohol and intranasal cocaine. Whereas the half-life of cocaine is approximately 40 minutes, the half-life of cocaethylene is 2.5 hours, which may explain why cocaine-related symptoms can continue for some time after cocaine is last used.

The human brain, heart, liver, and placenta bind cocaine and cocaethylene. As with cocaine, cocaethylene binds to dopamine and norepinephrine transporters and inhibits catecholamine reuptake (primarily norepinephrine) into nerve terminals. The increased "high" reported with the concurrent use of alcohol and cocaine may be the result of the additive effect of cocaine and cocaethylene. Yet another reason may be the relationship between these substances and serotonin. The binding of serotonin by cocaine may modulate the high and may be the cause of the dysphoric effects of cocaine. Cocaethylene, which is 40 times less potent than cocaine in binding to the serotonin receptor, does not share this negative property.

In dog studies, cocaethylene was a more potent precipitant of convulsions and cause of lethality than cocaine. This is probably because cocaethylene blocks sodium channels more potently than cocaine. Although the toxic level of cocaethylene in humans is not known, the LD50 in mice was 93 mg/kg for cocaine versus 60 mg/kg for cocaethylene. The process of cocaethylene formation continues for several hours, which may explain why sudden deaths may occur 6-12 hours after cocaine ingestion.

Cocaethylene, which is ultimately metabolized to benzoylecgonine, is not the only factor augmenting the effects of cocaine with ethanol. [7] Consumption of ethanol before cocaine use also increases the bioavailability of cocaine.

Signs et al present an exception to the weight of the literature in a study based on 57 ED patients who tested positive for both alcohol and cocaine. In these patients, systolic and diastolic BP, heart rate, and body temperature did not significantly differ between those testing positive for both alcohol and cocaine and drug-free control subjects. [8] This may be because long-term cocaine users reportedly develop tolerance to the cardiovascular effects of the drug. Signs et al concluded that the incidence of serious cardiovascular complications resulting from simultaneous use of cocaine and ethanol does not appear to be significantly higher than that observed in patients using only cocaine, only ethanol, or no drug. [8]

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