Additive, Synergistic and Antagonistic Consequences

Alcohol TestThere are always consequences in life resulting from decisions made or actions taken. When that decision involves combining alcohol and drugs, the consequences as a whole are often greater than the parts. That is just another way of saying that alcohol or drugs produce reactions, but when used together the potential combined effects can be greater than those experienced when they are not mixed.

Employers managing workplace drug and alcohol testing programs should be aware of certain terms that are used to categorize multi-substance interactions – additive, synergistic and antagonistic. The types of interactions are due to the mixing of drugs or the mixing of drugs and alcohol. The drugs can be legal prescription or non-prescription drugs or illegal drugs.

Additive – Alcohol potentiates or enhances the effects of drugs so the net effect is the sum of the effects from alcohol and the enhanced effects of the drugs

Synergistic – Alcohol used with the drug creates a drug effect that is greater than the sum of the effects from alcohol and the drugs

Antagonistic – Alcohol used with a drug creates a drug effect that is diminished

The actual affects of mixing drugs and alcohol are only predictable up to a point. For example, it is known that hallucinogens lead to altered perception of the senses. However, the senses most profoundly impacted and the severity of the hallucinations is different from person to person. When alcohol is added, the variability of effects is expanded, making them even more difficult to predict. This means that the risks to workplace safety are greatly increased when workers take legal or illegal drugs and also drink alcohol.

Three Times Dangerous

Last year, scientists conducted a study on the effects of alcohol on drugs in the body. They reported in Molecular Pharmaceutics that alcohol could make some prescription and non-prescription medicines three times more available to the body. It accomplishes this by changing how substances and enzymes in the body interact with the medications. In other words, in some cases workers mixing alcohol and drugs are taking the equivalent of three drug doses as a result of drinking alcohol. There are over 5,000 legal drugs in the marketplace, meaning it is almost impossible to learn every possible type of interaction that may occur.1

Of course, illegal drugs are often even more potentially hazardous for a lot of reasons, like the fact they have an unknown chemical composition due to lack of controls. No one really knows for sure what is being ingested when taking street drugs. There are some known likely interactions though, and they can seriously affect the ability of workers to remain alert, coordinated, and functional.

For example, alcohol increases the sedative effect of marijuana and opiates. Alcohol can increase the absorption rate of benzodiazepines, while also intensifying the depressant effect of the drugs on the Central Nervous System (CNS). The worker will likely experience a delayed reaction time, poor coordination, impaired memory, and aggression. Alcohol mixed with opiates like heroin can also increase the depressant effects on the CNS. Mixing barbiturates and alcohol creates a high potential for overdose because both substances can seriously depress the CNS, lowering consciousness. The additive effect means that the combined effects of alcohol and sedatives on the CNS are greater than the effects of each of the substances alone. Workers drinking alcohol and taking legal anti-anxiety, anti-depressants or muscle relaxants are more likely to get sleepy and dizzy, increasing the risk of having a work accident.2 Clearly, it is important to test workers for multiple drugs and alcohol.

Unpredictable Results Threaten Workplace Safety

In many cases, the results of mixing alcohol and drugs are just not predictable. Alcohol and benzodiazepines or opioids can lead to an additive or synergistic effect. It simply depends on the person. Alcohol mixed with cocaine can have an antagonistic or additive affect. In addition, stimulant drugs can lead to increased drinking because they mask the effects of alcohol. A person may not recognize how drunk he or she is getting and will continue drinking. Alcohol mixed with methamphetamine masks the effects of meth, making the person more likely to overdose on the drug.

Alcohol affects the way medications are metabolised, and mixing any drugs and alcohol is always dangerous. Drug and alcohol testing performed in the workplace is the only way to effectively maintain a substance free facility. The growing number of people combining drugs and alcohol (polydrug use) means it is important to do both types of testing.

CMM Technology ( offers employers a wide range of alcohol and drug testing equipment and testing kits to cover all types of work locations. They include breathalysers, the Lion Alcoblow, saliva drug tests, urine tests, and many others.


1 American Chemical Society. “Alcohol could intensify effects of some drugs in the body.” ScienceDaily, 26 Jul. 2012. Web. 11 Jan. 2013.

2 Health Department of Western Australia. (1999). Alcohol Interaction with Other Drugs. Western Australia Alcohol and Other Drugs Program – Public Health Division. Retrieved from

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