This resource has undergone expert review.

Polydrug Use: Factsheet

Polydrug Use
Year: Year 9–10, Year 11–12
Targeted Drugs:

What is it?

Mixing drugs or taking more than one drug at a time is known as polydrug use. Combining drugs in this way carries extra risks and can be extremely dangerous. The more drugs a person takes at one time, the more chance there is of something going wrong.

An example of polydrug use would be smoking cannabis after drinking 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).

Using more than one drug at a time makes the effects even more unpredictable. On top of 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:


Combining Stimulants

e.g. cocaine and MDMA/ecstasy


Serotonin syndrome


Anxiety or panic attacks

Heart problems


Combining Stimulants and Depressants

e.g. speed and alcohol


Heart problems

Respiratory infections and bronchitis

Dehydration, overheating, and kidney failure


Combining Depressants

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.

Evidence Base

This factsheet was developed following expert review by researchers at the Matilda Centre for Research in Mental Health and Substance Use and the National Drug & Alcohol Research Centre, UNSW.

Page last reviewed: 8 April 2019.