Drug interactions can be inhibitory, where one drug actually inhibits the actions of anther drug. It is important to distinguish this from drug interactions that are masking, meaning that the drugs disguise one another s effects. This can be dangerous because the user will not be aware of the drug since there is a lessened high, yet the drug will still be influencing their body and can still cause harm. In cases of drugs which mask one another overdose is a concern, as the user will not have a sense of when to stop ingesting the drug, or when their body has reached its limit. Interactions can be additive, meaning that the effects of both drugs are present and unhindered by one another.
Drug interactions can also be synergistic.
Synergistic interactions are those where the effects of the two drugs are multiplicative, rather than additive. The presence of two or more drugs in the body can keep the body so busy metabolizing one that metabolism of the second drug is delayed. For example, the presence of alcohol keeps the liver so busy that a Xanax or Seconol will remain in the body two or three times longer than normal. Depressant drugs always have a synergistic interaction. Exaggerated respiratory depression is the biggest danger with the use of alcohol and another depressant.