Part 2 of 6 in the "Chinese herbs and Western medication" series. All six are listed at the foot.

"Two hours apart" sounds like a line of defence. To know what it defends against and what it does not, you first have to see where a medicine goes once it is inside you.

Chinese and Western medicines can affect each other by six main routes — that is the Hong Kong Hospital Authority's sorting. The first four happen at the four stations a medicine passes, and this part takes those four. The last two are the effects themselves adding up or cancelling out, which is part 3.

The short version

• A medicine entering the body passes four stations: absorption in the gut, entry into the blood and distribution, metabolism in the liver, excretion by the kidneys — that is the route drawn in the Hospital Authority's lecture material.
• ① Absorption: acidic herbs meeting alkaline Western drugs, or the reverse, can react as acid and base; tannin-containing and mineral herbs form insoluble complexes with certain drug groups.
• ② Distribution: once absorbed, a medicine enters the blood. The active constituents of 黄连 and 黄柏 bind strongly to blood proteins, and taken with the anticoagulant warfarin the tendency to bleed increases — that is the Hospital Authority's example.
• ③ Metabolism: the liver station can be slowed down (the drug's level rises) or sped up (it falls). The same 黄连 appears under distribution in ② and metabolism in ③.
• ④ Excretion: the kidney station depends on acid and base. In the Hospital Authority's teaching example, a patient with a urinary tract infection added 山楂丸 on their own and crystals and blood appeared in the urine.
• All of these are the Hospital Authority's examples, not a list where anything unlisted is safe.

First, the one thing never to do

⚠️ A safety note: TCM and Western medicine complement each other. It is not a choice between them. This part names several Western medicines. Whichever one you recognise, never stop on your own — do not stop, reduce or adjust any prescribed Western medication because you read this, since changes to a prescription are decided by the doctor who wrote it. If you have a question, take the list and the question to the prescribing doctor.

The full account is in part 1.

A note: this section is general information only. For conditions like these, follow your doctor's diagnosis and treatment, and seek medical attention when you need it.

I. A medicine passes four stations in the body

A medicine entering the body passes four stations: absorption in the gut, entry into the blood and distribution through the body, metabolism in the liver, excretion by the kidneys. Those four are the route drawn out in the Hospital Authority's lecture material.

Those four stations are the pharmacokinetic half from part 1 — what the body does to a medicine. The first four routes take one station each, and each one below is illustrated with the Hospital Authority's own example.

II. The first two stations: the gut, and the blood

① Absorption: the reaction happens in the gut. Acidic herbs (山楂 hawthorn, 五味子 schisandra, 乌梅 dark plum) meeting alkaline Western drugs (such as antacids) can react as acid and base — the Hospital Authority groups those together.

Alkaline herbs (瓦楞子 ark shell, 牡蛎 oyster shell, 海螵蛸 cuttlebone) meeting acidic ones (such as aspirin, penicillin) do the same.

Tannin-containing herbs such as 大黄 rhubarb root, 虎杖 and 地榆 form insoluble complexes with tetracycline, erythromycin, vitamin B, digestive enzymes, and metal-ion drugs such as calcium, iron and antacids. That group is the Hospital Authority's.

Mineral herbs such as 石膏 gypsum, 自然铜 and 赭石 also form insoluble complexes with tetracycline and erythromycin. The Hospital Authority adds that some foods are also high in tannin.

Both reactions happen before the medicine is absorbed, which makes this station the one a one-to-two-hour gap mainly reaches.

② Distribution: in the blood. Once absorbed, a medicine enters the blood and is distributed through the body.

The active constituents of 黄连 (coptis) and 黄柏 (phellodendron bark) bind strongly to blood proteins; taken with the anticoagulant warfarin, the tendency to bleed increases. That is the Hospital Authority's example.

III. The last two stations: the liver, and the kidneys

③ Metabolism: the liver station slowed down or sped up. Some herbs inhibit metabolism, so the Western drug's level in the body rises.

姜黄 (turmeric) and 五味子 with tacrolimus may increase its side effects, such as constipation and headache. That is the Hospital Authority's example.

黄连 and 黄柏 with cyclosporine work the same way, inhibiting metabolism and raising the level, and may increase its side effects, such as raised blood pressure. That pair is its example too.

Other herbs speed metabolism up, so the level falls: in the same material, 甘草 (liquorice) with midazolam, and the drug's effect is reduced. Notice that the same 黄连 appears under distribution in ② and under metabolism in ③: one herb can travel more than one route.

④ Excretion: the kidney station depends on acid and base. An acidic herb with an alkaline drug (or the reverse) neutralises, raises the drug's solubility in water, speeds excretion and lowers the effect. That rule is written in the Hospital Authority's material.

Acid with acid, or alkaline with alkaline, lowers solubility, hinders excretion and increases the drug's action, especially its side effects on the kidneys. So is that one.

The Hospital Authority's teaching example: some sulfonamide antibacterials reach high concentrations in the urine as they are excreted, which suits them to treating urinary tract infection, but when the urine becomes more acidic their solubility falls, crystals form easily, and blood in the urine and reduced urine follow.

A patient with a urinary tract infection is prescribed sulfamethoxazole and trimethoprim; for indigestion the patient takes 山楂丸 hawthorn pills on their own (a digestive, acidic), and crystals and blood appear in the urine. That one is the Hospital Authority's teaching example too.

A note: this section is general information only. For conditions like these, follow your doctor's diagnosis and treatment, and seek medical attention when you need it.

IV. These are examples, not a list

These are the Hospital Authority's examples, not a list where anything unlisted is safe. One herb can appear under several routes (黄连, 甘草 and 山楂 all do), which is why the judgement is made on your whole medication list.

Do not stop or reduce any Western medication named in this part because you read this; take the list and the question to the prescribing doctor.

The words in this part

• Pharmacokinetics (药动学) — the Hospital Authority's gloss: what the body does to a medicine. All four stations in this part sit under it; the full account is in part 1.
• Tannin (丹宁／单宁) — the Hospital Authority files "tannin-containing herbs" as a group of their own, because that group forms insoluble complexes with tetracycline, erythromycin, vitamin B, digestive enzymes and metal-ion drugs. It also notes that some foods are high in tannin.
• Insoluble complex (不溶物) — the Hospital Authority's word for the result: two things meet in the gut and become something that will not dissolve in water. What will not dissolve is not easily absorbed.
• Anticoagulant: warfarin (华法林) — this is how the Hospital Authority labels it on its material: warfarin, 华法林, an anticoagulant. Part 4's table is headed by it.
• Sulfonamide antibacterials (磺胺类抗菌药) — the Hospital Authority's account: this group reaches high concentrations in the urine as it is excreted, which suits it to treating urinary tract infection; and it is that same concentration that makes crystals form easily when the urine is acidic.

Frequently asked

Why does one herb appear under several routes? Because a "route" describes a place in the body, not a property of the herb. 黄连 binds to blood proteins under ②, and inhibits metabolism in the liver under ③ — the Hospital Authority's material files it in two different places. So the question to ask is not "is this herb a problem" but "which station could go wrong given my medication list".

With tannin-containing herbs, is spacing enough? That does not follow. Forming an insoluble complex happens before absorption, and a one-to-two-hour gap reaches that station; ② to ④ happen after the medicine is inside the body, where a gap does not reach. Part 3 does that sum.

The other five parts

• Part 1: Can you take Chinese herbs with Western medication? The answer first, and the one thing never to do
• Part 3: How far apart is far enough — and the two routes a gap does not reach
• Part 4: Which Western drug classes need extra care: the two with a narrow window, plus blood-pressure and blood-glucose medication
• Part 5: Red yeast rice and statins: when the supplement contains the drug, and three more classes to mention
• Part 6: What actually happens at the consultation, and fitting it into life in Malaysia

👉 If you are on Western medication and want to know how Chinese herbs should be arranged around it, you are welcome to book an online consultation with HansMed, where a practitioner registered under the T&CM Act 2016 assesses it with your medication list in view. Make sure your doctor knows about the arrangement too; safety rests on both sides having the full picture.

Sit with a licensed TCM practitioner from wherever you are.

HansMed Modern TCM

Sources

• Hospital Authority, Hong Kong, Smart Patient lecture deck, 《當中藥師遇見藥劑師——認識中西藥相互作用》, PDF created 9 July 2024 — https://www.smartpatient.ha.org.hk/smart-patient-web/useful-information/sp-series/sp-series-details/%E8%97%A5-%E5%AF%86-%E8%A7%A3%E9%8E%96%E8%AC%9B%E5%BA%A7
• Hospital Authority, Hong Kong, HASLink July 2024, "中西藥相互作用知多少" — https://www3.ha.org.hk/ehaslink/issue132/tc/feature-3.html

本文是「中药和西药」系列的第 2 篇，共 6 篇。六篇的清单在文末。

「隔两小时」听起来像一道防线。要知道它防得住什么、防不住什么，得先看一颗药进了身体以后会去哪里。

中西药会互相影响，主要有六种方式——这是香港医院管理局的归纳。前四种发生在药在身体里走的四站，这一篇讲这四站；后两种是作用本身的叠加与抵消，在第 3 篇。

一分钟看完

• 一颗药进入身体会经过四站：胃肠吸收、进入血液并分布、肝脏代谢、肾脏排泄——这是医院管理局讲座材料里的走法。
• ① 影响吸收：偏酸的药材遇上偏碱的西药（或反过来）可发生酸碱反应；含丹宁的药材与矿物药材，会与某几类西药形成不溶物。
• ② 影响分布：药被吸收后进入血液。黄连、黄柏的有效成分与血液中的蛋白质高度结合，与抗凝血药 warfarin 合用，出血倾向增加——这是医院管理局举的例子。
• ③ 影响代谢：肝脏这一站可以被减速（西药浓度升高）或加速（浓度降低）。同一味黄连，在②是分布，在③是代谢。
• ④ 影响排泄：肾脏这一站看酸碱。医院管理局的教学例子里，一位泌尿道感染的病人自行加服山楂丸，出现了结晶尿与血尿。
• 这些都是医院管理局举的例子，不是「没列到就安全」的清单。

先说绝对不要做的一件事

⚠️ 安全提醒：中医与西医是互相补位的关系，不是二选一。这一篇点名了好几种西药。看到哪一种，都切勿自行停药——不要因为读到这里就自行停用、减量或调整任何西医处方药，处方药的调整只能由开立那个处方的医师决定。有疑问，带着药单问开药的医生。

完整说明见第 1 篇。

小提醒：本段仅为一般知识说明。相关情况请以西医的诊断与治疗为主，并在需要时及时就医。

一、一颗药在身体里要经过四站

一颗药进入身体，会经过四站：胃肠吸收、进入血液并在体内分布、肝脏代谢、肾脏排泄。这四站是医院管理局讲座材料里画出来的路。

这四站就是第 1 篇说的药动学——人体对药物的作用。前四种方式一种对一站，下面每一种都用医院管理局自己举的例子说明。

二、前两站：胃肠道，和血液

① 影响吸收：在胃肠道就起反应。 偏酸的药材（山楂、五味子、乌梅）遇上碱性西药（如制酸剂），可发生酸碱反应——医院管理局把这一组列在一起。

偏碱的药材（瓦楞子、牡蛎、海螵蛸）遇上酸性西药（如 aspirin、penicillin），也一样。

含丹宁（单宁）的药材，如大黄、虎杖、地榆，与四环素、红霉素、维他命 B、消化酶，以及钙剂、铁剂、制酸剂这类含金属离子的西药，会形成不溶物。这一组是医院管理局列的。

石膏、自然铜、赭石这类矿物药材，与四环素、红霉素也会形成不溶物。医院管理局补了一句：某些食物也含较多丹宁。

这两种反应都发生在药被吸收之前，所以这一站是「隔开一至两小时」主要管得到的地方。

② 影响分布：在血液里。 药被吸收后进入血液，在体内分布。

黄连、黄柏的有效成分与血液中的蛋白质高度结合；与抗凝血药 warfarin（华法林）合用，出血倾向增加。这是医院管理局举的例子。

三、后两站：肝脏，和肾脏

③ 影响代谢：肝脏这一站被减速或加速。 有的药材抑制代谢，西药在体内的浓度升高。

姜黄、五味子对 tacrolimus（他克莫司），可能增加它的副作用，如便秘、头痛。这是医院管理局举的例子。

黄连、黄柏对 cyclosporine（环孢菌素），同样是抑制代谢、浓度升高，可能增加它的副作用，如血压升高。这一组也是它举的例子。

也有药材促进代谢，西药浓度降低：同一份材料里，甘草对 midazolam（咪达唑仑），药效降低。留意同一味黄连，在②是分布，在③是代谢——一味药材可以走不止一条路。

④ 影响排泄：肾脏这一站看酸碱。 酸性药材配碱性西药（或反过来），酸碱中和，药物在水中的溶解度提高，排泄加快，药效降低。这一条写在医院管理局的材料里。

酸配酸、碱配碱，溶解度降低，不利于排泄，药物作用增加，尤其是对肾脏的副作用。这一条也是。

医院管理局的教学例子：某些磺胺类抗菌药排泄时在尿中浓度高，适宜治疗泌尿道感染，但尿液酸性增加时溶解度降低，容易析出结晶，引起血尿、尿少。

病人患泌尿道感染，西医处方 sulfamethoxazole 和 trimethoprim；因消化不良自行服食山楂丸（消食药，偏酸），结果出现结晶尿、血尿。这一段也是医院管理局的教学例子。

小提醒：本段仅为一般知识说明。相关情况请以西医的诊断与治疗为主，并在需要时及时就医。

四、这些是例子，不是清单

这些是医院管理局举的例子，不是「没列到就安全」的清单。同一味药材可以出现在好几种方式里（黄连、甘草、山楂都是），所以判断要看您的整份药单。

本篇提到的任何西药，都不要因为读到这里而自行停用或减量；有疑问，带着药单问开药的医生。

这篇出现的几个词

• 药动学（pharmacokinetics）——香港医院管理局的说法：人体对药物的作用。这一篇的四站全在这一类里；完整说明在第 1 篇。
• 丹宁（单宁，tannin）——医院管理局把「含丹宁中药」单独列成一组，因为这一组与四环素、红霉素、维他命 B、消化酶和含金属离子的西药会形成不溶物。它也指出某些食物含较多丹宁。
• 不溶物——医院管理局用来称呼这种结果的词：两样东西在胃肠道里凑在一起，变成不溶于水的东西。不溶，就不好吸收。
• 抗凝血药 warfarin（华法林）——医院管理局在材料上就是这样标注它的：warfarin，华法林，抗凝血药。第 4 篇的表格由它领头。
• 磺胺类抗菌药（sulfonamides）——医院管理局的说明：这类药排泄时在尿中浓度高，适宜治疗泌尿道感染；也正因浓度高，尿液偏酸时容易析出结晶。

常见问题

同一味药材为什么会出现在好几种方式里？ 因为「方式」说的是身体里的位置，不是药材的属性。黄连在②是与血液中的蛋白质结合，在③是抑制肝脏代谢——医院管理局的材料把它填在两个不同的位置上。所以该问的不是「这味药有没有问题」，而是「我这份药单里，哪一站可能出事」。

含丹宁的药材，是不是只要隔开就没事？ 不能这样推。形成不溶物发生在吸收之前，隔开一至两小时管得到这一站；②到④发生在药进入身体之后，隔开管不到。第 3 篇算这笔账。

这个系列的另外五篇

• 第 1 篇：中药和西药可以一起吃吗？先给答案，和绝对不要做的那一件事
• 第 3 篇：隔多久才够？以及间隔管不到的那两种方式
• 第 4 篇：哪几类西药要特别小心：治疗窗窄的两种，加上降血压药与降血糖药
• 第 5 篇：红曲与他汀：保健品里就有同一种成分，以及另外三类要说清楚的药
• 第 6 篇：看诊时实际会发生什么，以及大马生活里怎么安排

👉 如果您正在吃西药，想知道中药该怎么安排，欢迎透过汉方中医的线上问诊，由依 2016 年 T&CM 法令注册的医师看着您的药单为您评估。请同时让您的医生知道这个安排，两边都掌握资讯，才是安全的前提。

无论身在何处，与持证中医师对坐。

汉方现代中医

资料来源

• 香港医院管理局「智友站」讲座简报，《當中藥師遇見藥劑師——認識中西藥相互作用》，PDF 建档 2024 年 7 月 9 日 — https://www.smartpatient.ha.org.hk/smart-patient-web/useful-information/sp-series/sp-series-details/%E8%97%A5-%E5%AF%86-%E8%A7%A3%E9%8E%96%E8%AC%9B%E5%BA%A7
• 香港医院管理局，《协力》2024 年 7 月号〈中西药相互作用知多少〉— https://www3.ha.org.hk/ehaslink/issue132/tc/feature-3.html