Sweden has one of the world's highest percentages of lactase tolerant people. 其中瑞典为乳糖耐受性比例最高的国家。
Moreover, they can have serious side effects, and patients tend to become tolerant to them, requiring escalating doses to get any relief at all. 再者,它们都可能有严重的副作用,病人也经常对它们产生耐受性,必须使用更高剂量才能获得止痛疗效。