A hypnotic drug that seems to be free of dependence or abuse liability is the amino acid l-tryptophan. It has not been formally approved for medical use as a hypnotic drug in the United States, but it was available in both drugstores and health food stores as a dietary supplement, either in the pure form or combined with other nutriments. There was reasonable evidence that, at doses of 1–6 g at bedtime, l-tryptophan had some efficacy as a sleeping pill in some patients with insomnia. It was neither as powerful as the major hypnotics nor, presumably, as dangerous. It would be, however, a rather expensive way to get a night's sleep, because the drug used to cost (in the 1980s) almost $1 per gram.