The effects caused by a combination of two or more substances are almost impossible to assess. As a rule, they do not correspond to the sum of the individual effects: Mixing involves additional, sometimes high health risks. Depending on the substance, the respective effects are amplified (sometimes many times over), or they influence the body and psyche in different directions. Both are extremely stressful for the users. The risk of unpleasant incidents is increased by mixed use. Those who mix substances should avoid particularly risky combinations (see Combi Checker).
In any case, it is important to first know the effects of the substances individually and at least wait for the full effect of one substance before consuming the next. Remember that different substances take different amounts of time to reach their maximum effect.
Because of the high strain on the liver and kidneys, it is important to drink plenty of (non-alcoholic) fluids. Alcohol generally alters the effect of other psychoactive substances.
If you use uppers (e.g. amphetamine) to delay coming down, you increase the hangover. Downers to come down also prolong the hangover and usually have a high potential for dependence.
The principle of drug, set and setting should be observed.
It is advisable to tell friends or acquaintances in advance which substances have been mixed during consumption.
Anyone taking medication should seek medical advice in advance about possible risky interactions with psychoactive substances (impairment of the effectiveness of the medication, serious complications, etc.).