synchill oral horse calming gel (single dose, 5 ml) synnutra equine synchill was developed to reduce stress and anxiety in horses without impeding performance. given 1-2 hours prior to a stressful event, it helps horses relax, focus and perform. synchill contains no drugs or banned substances. a proprietary blend of 5-htp, vitamin b6 and melatonin are used to increase serotonin in the central nervous system to calm nervous horses. synchill uses a very small volume because, unlike tryptophan, 5-htp freely crosses the blood-brain barrier for a quick and direct calming effect.