Tryptophan loading may reverse tolerance to opiate analgesics in humans: A preliminary report

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Abstract
Five patients on chronic opiate medication to treat low-back and leg pain developed opiate tolerance, based on their failure to obtain significant relief (rated on a subjective pain scale and by degree of straight leg-raising they could endure) after receiving 30 mg morphine i.v. in divided doses over 35 min. After these patients'' diets had been supplemented with 4 g/day of L-tryptophan for 2-9 wk, they achieved significant relief from pain when the opiate tolerance test was readministered and could lead more active lives while reducing daily opiate intake. Chronic opiate administration reduces serotonin turnover rate in CNS. This may be reversed by loading with the serotonin precursor, L-tryptophan.