毒药还是解药？中医表明，环境可以改变一切

概要

毒药在中医中的使用历史已有两千多年，这与毒药通常给人带来的伤害和危险形成了鲜明对比。许多人对传统中药的安全性和有效性持怀疑态度，认为其中的药物可能含有对健康有害的隐性毒性成分。然而，毒药与药物之间的界限模糊不是中医专有的现象。化疗使用有毒药物来治疗癌症，而某些被视为非法的迷幻药物在医学界引发了新的兴趣。

关于传统中药的安全性和有效性的争论通常集中在药物的活性成分上。美国食品和药物管理局将有效成分定义为在诊断、治愈、减轻、治疗或预防疾病方面提供药理活性或其他直接作用，或影响人或动物身体结构或任何功能的任何成分。这意味着活性成分被视为药物的本质，在现代制药学中用作评估药物效用的黄金标准。

虽然在药物发现过程中发现活性成分是有价值的，但将一种药物简化为单一分子的方法是有限的，因为这种简化方法忽视了药物的使用环境对其效果的重要影响。毒药的历史使用可以帮助我们理解这一观点，毒药的效果不仅仅在于其活性成分，还取决于配制和使用方法。

古代中国医生意识到，毒药的效果与配制和使用方法密切相关。他们开发了各种方法，如剂量控制、与其他成分混合以及其他药物加工技术，以减轻毒药的毒性，但仍保持其药效。他们还意识到，毒药的作用因人而异，同一种药物因病人的不同特点而产生不同的效果。传统中药中的毒药被用于治疗各种疾病，例如乌头和水银被广泛应用于中世纪的药方中。然而，对毒药的滥用超出了其限制范围，导致了无数人的死亡。这说明药物的正确使用和使用环境是至关重要的。

传统中药以毒攻毒的思想揭示了一个重要观点，即药物的效果并不存在本质的、绝对的或不变的特征，而是与药物的使用方式、与特定身体的相互作用以及预期效果相关。超越活性成分的生物医学标准有助于更加关注药物的使用环境，使人们对治疗有更细致入微的理解。

Poison or cure? Traditional Chinese medicine shows that context can make all the difference

Poisons today typically evoke notions of harm and danger – the opposite of medicines for healing. Yet traditional Chinese medicine, which has been in practice for over two millennia, used a large number of poisons to treat a variety of illnesses. Chinese doctors knew that what makes a drug therapeutic isn’t just its active ingredient – it depends on how you use it.

Biomedical researchers skeptical of the safety and efficacy of traditional Chinese medicine might not be surprised that Chinese doctors historically prescribed poisons. Some believe that the drugs used in traditional Chinese medicine often contain hidden toxic ingredients detrimental to health.

But this blurred boundary between poison and medicine is not unique to traditional Chinese medicine. Chemotherapy uses toxic drugs to treat cancer. And the U.S. opioid epidemic offers a sobering reminder of how a class of FDA-approved medicines used to treat chronic pain became lethal poisons through improper administration. Conversely, certain psychedelics deemed illegal today have ignited new interest in the medical community as potential treatments for anxiety, addiction and depression.

I am a medical historian who examined the therapeutic use of poisons in Chinese medicine in my recent book. Based on my research, I believe that Chinese doctors in the past recognized the healing capacity of poisons while being fully aware of their potential to kill. Understanding this practice compels modern biomedicine to reconsider how “medicine” is defined today.

What is an active ingredient?

The debate on the safety and efficacy of traditional Chinese medicine often centers on the active ingredient of a drug. The U.S. Food and Drug Administration defines an active ingredient as “any component that provides pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body of man or animals.”

In other words, the active ingredient is a specific chemical considered to make up the essence of a drug. Because it carries the responsibility of curing a target disease, it’s used as the gold standard to evaluate the utility of a drug in modern pharmaceutics.

Understanding the poison-medicine paradox opens up more doors for treatment. Mike Kemp/Corbis News via Getty Images

There is value to identifying active ingredients in drug discovery, including those in traditional Chinese medicine. Scientist Tu Youyou won the 2015 Nobel Prize in Physiology or Medicine for isolating malaria drug artemisinin from an herb used in traditional Chinese medicine. In the same vein, medical researcher Zhang Tingdong and his team identified arsenic trioxide as an effective treatment for leukemia by studying drug formulas in traditional Chinese medicine.

Despite these success stories, reducing a medicine to a single molecule is rather limited. This reductionist approach ignores the context in which a drug is used, which plays a crucial role in its end effects. To appreciate this perspective, it is necessary to go back in history to see how poisons were understood and used in premodern China.

Poisons in traditional Chinese medicine

The Chinese word for poison is “du” (毒). Unlike its negative meaning today, ancient texts written 2,000 years ago used the word to denote potency, or the ability to both harm and heal. There was no categorical distinction between poisons and nonpoisons in traditional Chinese medicine – they acted in a continuum defined by level of potency.

Aconite is a poisonous herb that was used to treat cold symptoms in ancient Chinese medical practice. Library of Congress, Asian Division, Chinese Rare Books

The dual potential of poisons laid the foundation for their use in medicine. Chinese doctors strategically deployed potent poisons to cure everything from blood clots to abdominal pain to epidemic diseases. For example, aconite (“fuzi”附子), a highly poisonous herb grown in southwest China, was one of the most often prescribed medicines in the medieval era. Mercury was another poison used regularly in both medicine and alchemy to eliminate worms and prolong life. Overall, poisons consistently made up about 20% of the drugs in the ever-expanding Chinese pharmacopeia throughout the imperial era, speaking to their crucial role in healing.

One way Chinese doctors used poisons for healing was through the principle of using poison to attack poison (“yi du gong du”以毒攻毒). In their eyes, these powerful substances could target and eliminate specific disease entities like worms inside the body. They believed the strong sensations induced by poisons marked a process of purifying the body of its harmful burdens.

The context in which a drug is used matters

Chinese doctors in the past were not looking for an active ingredient that defined the usefulness of any given substance. Rather, they considered the effect of each drug highly malleable. No better example illustrates this way of thinking than the medical use of poisons.

Illustration of drug processing in a 16th-century pharmaceutical text. Wellcome Collection

Doctors in China were keenly aware of how the effect of a poison varied greatly depending on how it was prepared and administered. Accordingly, they developed a variety of methods – such as dosage control, mixing with other ingredients and other drug processing techniques – to mitigate a poison’s potency but still preserve its efficacy.

Chinese doctors were also aware that poisons worked differently from person to person. The same drug could have different effects depending on the patient’s gender, age, setting, emotional status and lifestyle. For example, eminent 7th-century physician Sun Simiao (孫思邈) offered remedies specific to women and the elderly.

Using a poison outside of its prescription often proved deadly. For instance, Five-Stone Powder, or “Wushi San”(五石散), a psychedelic drug that contains arsenic, was one of the most popular medicines in medieval China. Despite medical recommendation that it be used only as a last resort to treat emergencies, many at the time regularly consumed it to invigorate their bodies and illuminate their minds. Unsurprisingly, this misuse led to numerous deaths. Going beyond its restricted usage, a poison could easily kill.

Beyond the active ingredient

The paradox of healing with poisons in traditional Chinese medicine reveals a key message: There is no essential, absolute or unchanging core that characterizes a medicine. Instead, the effect of any given drug is always relational – it is contingent on how the drug is used, how it interacts with a particular body and its intended effects.

Medicines are fluid substances that defy stable categorization. Looking beyond the biomedical standard of the active ingredient could help doctors and researchers pay more attention to the context of how medicines are used. This will allow for a more nuanced understanding of healing.

Ultimately, there is more to a medicine than its active ingredient. Poisons in traditional Chinese medicine, I hope, teach a compelling lesson.

Source：

The Conversation

Published on 23 August, 2021

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