According to experts who have conducted a battery of tests on this supplement, the biological half-life of l-5-hydroxytryptophan teeters between 2.2 to about 7.4 hours when used to manage stress. The rate of plasma clearance, on the other hand, revolves around 0.1 to 0 25 1/kg/hour. In other words, this means that the effects of hydroxytryptophan will have cleared in about a day or so. And this explains why the recommended dosage of taking 2 capsules within 24 hours exists.