What adverse reaction should be considered when combining St. John's wort with selective serotonin reuptake inhibitors?

When combining St. John's wort with selective serotonin reuptake inhibitors (SSRIs), it is crucial to consider the potential for dangerous drug interactions. St. John's wort is known to induce cytochrome P450 enzymes, particularly CYP3A4, and can affect the metabolism of many medications, including SSRIs. This induction can lead to decreased effectiveness of the SSRIs or increased side effects due to altered drug levels in the body.

In addition, both SSRIs and St. John's wort can increase serotonin levels. When taken together, they raise the risk of serotonin syndrome, a potentially life-threatening condition characterized by symptoms such as confusion, agitation, rapid heart rate, and increased muscle tone. This type of interaction highlights the significance of monitoring patients closely when these substances are used concurrently.

The combination of St. John's wort and SSRIs necessitates caution due to these interactions, ultimately making this the most relevant adverse reaction to consider in this scenario.