Objectives:
Assessment of adverse drug interactions with herbal preparations (HP), i.e., plant medicines and nutritional supplements which contain plant extracts.

Methods:
Analysis of 147 cases of adverse events with clinical picture indicating probability or certainty of resulting from inclusion of HP into the applied pharmacotherapy (mostly psychotropic drugs).

Results:
The most common effect of interactions between SSRI or SNRI antidepressants and HP were hemorrhagic complications associated with Japanese ginkgo biloba (27.45% of complications in this subgroup). Another common complication was serotonin syndrome (SS) (11.8%) occurring during the use of ginseng (one case of SS after the addition of bacopa). In the group of antipsychotic drugs, the highest number of interactions was observed in the case of haloperidol, and the highest number of complications (29.8%) was associated with ginseng (including 6 cases of ventricular arrhythmias in combination with haloperidol), milk thistle (including 7 cases of pancreatitis in combination with haloperidol or risperidone, 1 case of hepatotoxicity after adding aripiprazole) and rhodiola rosea. As for hypnotics and sedatives – interactions with ginseng were most frequently reported, mainly intensified sedative effects, cognitive disorders and disturbances in consciousness. In 132 cases, withdrawal of the plant preparation resulted in a decrease in the severity of the reported adverse reactions or a complete resolution of the described symptoms.

Conclusions:
HP (especially ginseng, rhadiola rosea, ginkgo biloba, milk thistle) are associated with a significant risk of pharmacokinetic and pharmacodynamic interactions with psychotropic drugs. Because of the resulting complications and side effects, any decision to include a herbal supplement should be preceded by a detailed safety analysis with benefit and risk assessment.