What happens when you take nortriptyline with st. john's wort?
Nortriptyline is a secondary-amine tricyclic antidepressant used for depression, neuropathic pain, migraine prevention, and sometimes smoking cessation or insomnia. It is the active metabolite of amitriptyline but tends to be better tolerated because it has less anticholinergic and sedating activity. Nortriptyline is metabolized primarily by CYP2D6 (high affinity) and CYP3A4 (low affinity).
St. John's wort is a herbal extract from Hypericum perforatum that contains hyperforin and hypericin. Hyperforin is a powerful activator of the pregnane X receptor, which upregulates CYP3A4, CYP2C9, CYP2C19, and the P-glycoprotein transporter. With chronic dosing of about 10 to 14 days, St. John's wort significantly accelerates the metabolism of many drugs cleared by these enzymes.
When the two are taken together, two effects occur: first, nortriptyline plasma concentrations drop because the inducing herb speeds its breakdown; second, the herb adds extra serotonergic tone on top of nortriptyline's serotonin-reuptake blockade, raising the theoretical risk of serotonin syndrome.
Why is this important?
Nortriptyline has one of the better-defined therapeutic windows in the TCA class. Plasma concentrations between roughly 50 and 150 ng/mL are most often associated with antidepressant response, and levels above 150 ng/mL can produce confusion or cardiac conduction problems. Anything that shifts blood levels in either direction matters clinically.
St. John's wort tends to push nortriptyline blood levels down. Patients may feel that their medication has "stopped working" and may not connect the change to the supplement. Conversely, if St. John's wort is stopped abruptly, enzyme induction takes 1 to 2 weeks to reverse, during which nortriptyline levels can climb back up or even overshoot. Tricyclic antidepressants in toxic concentrations can cause QRS widening, QT prolongation, hypotension, and life-threatening arrhythmias.
The serotonergic effect is less severe with tricyclics than with SSRIs but still relevant. Symptoms of serotonin syndrome include tremor, sweating, agitation, fever, increased reflexes, and confusion. While reported cases with St. John's wort plus TCAs are rarer than with SSRIs, the mechanism is plausible and the combination is consistently flagged as a major interaction.
What should you do?
If you are prescribed nortriptyline, do not start St. John's wort. Choose a different mood support strategy, such as therapy, exercise, light therapy, or an additional prescribed medication recommended by your provider. If you are already taking both, schedule an appointment with your prescriber to plan a controlled wash-out of the herb rather than stopping it cold turkey.
- Disclose every supplement and herbal product to your prescriber and pharmacist.
- If you stop St. John's wort, your prescriber may want to recheck a nortriptyline blood level after about 2 weeks because the level will likely rise.
- Watch for both directions of problems: returning depression or pain (level too low) and confusion, agitation, palpitations, or dry mouth (level too high).
- Avoid combining nortriptyline with other serotonergic drugs (SSRIs, SNRIs, tramadol, triptans, MAOIs) unless specifically directed by your prescriber.
Which specific products are affected?
This warning applies to all nortriptyline products, including generic nortriptyline hydrochloride capsules and brand-name versions like Pamelor and Aventyl. The mechanism applies to the entire tricyclic class, so amitriptyline, imipramine, desipramine, clomipramine, doxepin, and trimipramine are all affected.
St. John's wort is sold as standalone capsules, tinctures, teas, and as an ingredient in many "mood," "calm," "stress," and "PMS" combination supplements. Common branded products include Kira, Perika, Movana, and many drugstore generics. Always read the full ingredient list of any herbal supplement before adding it to a medication regimen.
The bottom line
Combining nortriptyline with St. John's wort can both lower the effectiveness of the antidepressant and increase the risk of serotonin-related side effects, and stopping the herb without coordinating with a prescriber can cause nortriptyline levels to climb into a toxic range. Avoid the combination and tell your healthcare team about every supplement you take.