The interaction was still there two weeks after stopping
Hyperforin has a blood half-life of about nine hours. Two weeks after transplant patients stopped the herb they still needed a higher daily anti-rejection dose than at the start.
What the study found
Hyperforin clears in hours; what it switched on stays switched on
Hyperforin has a blood half-life of about nine hours and does not accumulate with repeated dosing. Two weeks after transplant patients stopped the herb, they still needed a higher daily dose of their anti-rejection drug than when they began. The enzymes had not switched back.
The caveat · One follow-up check, in ten patients
The two-week figure comes from a single follow-up measurement in ten patients, so it is a lower bound on how long the effect lasts rather than a measured rate of decay. The half-life figure was produced and published by an extract manufacturer, and its abstract never states how many volunteers it came from.