机器人药片有望给糖尿病患者带来福音

    皮肤。皮肤是一个坚实致密的组织，用来保护人体免受外物伤害。虽然理论上药物也能通过皮肤被人体摄取，但是像分子一样大的胰岛素需要电力刺激才能穿透皮肤。因此这种方法又贵又不实用。另外也有人尝试通过用药物舒张毛孔的方式来给药，但是多年来毫无进展。

    鼻粘膜。已经有通过鼻粘膜成功使用胰岛素的先例，但是对于日常使用来说，鼻粘膜还是太脆弱了。

    口腔内壁。它也是一种有弹性的粘膜，而且也具有吸收能力（想一想咀嚼式的烟草）。把溶解状态的胰岛素通过像哮喘喷剂一样的工具喷入口腔，已被证实是一种可以快速将胰岛素吸收到血液中的方法。这也是一种很有希望的方法，目前正在美国和印度接受试验。

    肺。几年前通过肺部吸收胰岛素的方法被研究了出来，但这种方法的隐患是，长期使用可能导致肺部损伤。美国药监局（FDA）虽然批准了这种方法，但要求患者必须定期接受肺功能检查。不过由于经济上并不实惠，再加上医生很少使用这种疗法，导致这种疗法最终退出了市场。另一种类似产品已经研究了一段时间了，而且不久即将接受FDA的审查。

    既然这些方法都不管用，为什么不把胰岛素做成口服药呢？这听起来是个简单的答案，但实际上却并不这么简单。首先，就像有的人有复发烧心症状，有的人有肠道易激综合症一样，人的胃肠系统存在很大的个体差异。

    其次是“汉堡包综合症”。人吞下胰岛素药片后，它必须先经过胃部的酸性环境的折磨，然后再在十二指肠中被消化酶“洗礼”一遍，然后再进入肠道，最后才能进入血液。另外胰岛素还要经过肝脏，有可能药物还没接触到血液和人体组织，就已经被肝脏破坏和分解了。

    许多药企都尝试过研制胰岛素片剂，但最后都以失败告终，但现在仍有一些制药公司依然在锲而不舍地研制最终能被血液吸收的口服胰岛素。但我对他们的尝试仍然持怀疑态度。

    我们再回来看看文章开头提到的机器人药片。它基本上就是一个聚合物胶囊，里面装着很多用糖做的微型空心针。胶囊像普通药物一样吞入腹中后，可以安然进入肠道。一旦进入小肠，人体的酸性物质就会溶解胶囊的外层，露出的微型气球状结构会不断膨胀，轻轻地将装满药物的针头推进肠壁。

    这是一个非常有趣的概念，很可能发展成一个有效的给药系统，但它离真正投入市场还有很远。它在胰岛素上的应用也仍然有待观察。（财富中文网）

    本文作者吉拉尔德•伯恩斯坦博士是纽约市西奈山以色列医疗中心弗里德曼糖尿病研究所糖尿病管理项目的主任，曾任美国糖尿病协会主席。

    译者：朴成奎

    Skin.The skin is a tough, dense tissue that protects our body by keeping foreign material out. Drugs can be delivered through the skin, but a large molecule like insulin needs a supplemental electrical force to pierce the skin. This is expensive and impractical. There have been attempts to use a patch with chemicals that open the pores, but over years it has not moved forward.

    Nasal membranes.Insulin has been successfully delivered through the nasal membranes, but they are too fragile for regular use.

    Lining of the mouth.This is a resilient membrane that also has absorptive capacity (think chewing tobacco). Insulin in solution has been sprayed into the mouth using an asthma-like inhaler that enables rapid absorption into the blood stream. This is a promising avenue that is undergoing tests in the U.S. and India.

    Lungs.A few years ago delivery to and through the lungs was developed, but there are and were concerns about long-term usage and lung damage. The FDA approved it but only with regular periodic pulmonary function tests. The financial impracticality and limited prescribing led the producer to take it off the market. Another product has been under study for some time and will be reviewed by the FDA.

    So if none of these really work, why not deliver insulin in a pill? Seems like a simple answer, but it's anything but. For one thing, as anyone with recurrent heartburn, irritable bowel and the like knows, no two days in the GI tract are the same.

    Then there's the hamburger syndrome. When insulin is swallowed, it must pass through the vicious acid environment of the stomach, then through the equally vicious pool of digestive enzymes in the duodenum, then finally onto and through the lining of the intestines before it enters the bloodstream. Insulin must also pass through the liver, where it may be destroyed or sequestered before reaching the general blood flow and the body's tissues.

    Many companies have tried and failed to package insulin in a pill, and several new systems designed to protect insulin from the body are under development. I remain skeptical.

    Which brings us back to the robotic device mentioned at the start, which is basically a capsule consisting of a polymer shell and a cargo of tiny, hollow needles made of sugar. Like a typical pill, the capsule is swallowed and makes its way through the GI tract. Once it reaches the small intestine, acids in the body dissolves the outer layer of the capsule, freeing a balloonlike structure that expands and gently pushes the drug-filled needles into the wall of the intestine.

    It is an interesting concept that could have legs as a drug-delivery system, but it's a long way from market. Its application to insulin also remains to be seen.

    Dr. Gerald Bernstein is director of the Diabetes Management Program at Friedman Diabetes Institute at the Mount Sinai Beth Israel Medical Center in New York City and past president of the American Diabetes Association.