Final answer:
Inform Caitlin's primary care provider about her use of St. John's wort due to potential drug interactions with psychiatric medications.
Step-by-step explanation:
Your response to make sure to let Caitlin's primary care provider know that she is taking St. John's wort is guided by the knowledge of potential drug interactions with psychiatric medications. St. John's wort is known to interact with various medications, including selective serotonin reuptake inhibitors (SSRIs) commonly used to treat depression. Informing the primary care provider is essential to ensure the safe and effective management of Caitlin's symptoms.