Codeine has greater and more predictable oral bioavailability, making it easier to titrate the dose. Thiosulfate is used, with a starch indicator, to titrate the iodine. As naltrexone has a longer half-life, it is more difficult to titrate. The side chain of tryptophan does not titrate. It can also be used to titrate procyanidins. It can also be used to titrate proanthocyanidins.