What is it?
Mixing drugs or taking one drug when under the influence of another drug is known as polydrug use. Combining drugs in this way carries extra risks and can be extremely dangerous. The more drugs a person takes (or is affected by) at a time, the more chance there is of something going wrong.
An example of polydrug use would be smoking cannabis while under the influence of alcohol. Mixing alcohol with drinks that contain caffeine is another example.
What are the effects?
The effect of mixing drugs depends on which drugs are mixed together. The effects of one drug are hard to predict and are affected by:
- The drug itself (e.g. its purity, amount used, frequency of use, how the drug is used, whether the drug has been cut, or mixed with another drug)
- The person who is using the drug (e.g. their mood, expectations, personality and individual characteristics)
- The setting (e.g. where the person is, the people they are with)
Being under the influence of more than one drug at a time makes the effects even more unpredictable. In addition to all the factors listed above, the effect of mixing drugs depends on which drugs are mixed together. Combining drugs that have the same physical effects (e.g. two or more stimulants, or two or more depressants) is especially dangerous. This is because it increases the impact on the normal functioning of the brain and body.
Below are some possible effects of combining different combinations of drug types:
e.g. cocaine and MDMA/ecstasy
Anxiety or panic attacks
Combining Stimulants and Depressants
e.g. speed and alcohol
Respiratory infections and bronchitis
Dehydration, overheating, and kidney failure
e.g. benzodiazepines and alcohol
Accidents or injury through being 'out of it'
Fatal overdose as a combination of depressants working together to slow down both the heart and breathing rate.
Nonfatal overdose, which can result in permanent brain damage.
This factsheet was developed following expert review by researchers at the NHMRC Centre of Research Excellence in Mental Health and Substance Use and National Drug & Alcohol Research Centre, UNSW.