Britain gets into the drug trade

That's how you win a trade war. Start a drug war on the side of drugs.

https://en.wikipedia.org/wiki/Opium_Wars

History can affect the words of a language.
In Chinese, a substance is either 药 (Medicine) or 毒品 (Poisonous Products), there is not a term such as "drug" that can fit into both contexts by adding other descriptive words such as in the terms "Legal Drugs" and "Illegal Drugs". A "drug store" if literally translated, would imply a place that sells illegal substances since "drug" is often translated to "Poisonous Products". So a new Chinese immigrant would think someone is talking about illegal drugs if they hear the term "drug store" and not as in "Pharmacy".
When Chinese People hear about legalization/decriminalization of drugs, in Chinese, that'd be: "美国合法化毒品" "The United States is Legalizing Poisonous Products"
So this is why legalizing weed will never happen in a country like China. Its literally referred to as a "Poison".
- Does this cause problems with abuse of medicine in China? Medicine usually is poison admitted in a small portion.
  
  It would be ~~药物乱用~~ 药物滥用 (Misuse of Medicine), if its actually something a doctor prescribed, or over the counter. No one hearing this term would ever think of cocaine or anything like that. Unlike "drug abuse" which could imply illegal drugs.
  But it'd be 吸毒 (ingesting poison), if its like weed, cocaine, etc... You don't even need the term "Misuse", is already implied that is bad because its labeled as a poison
  So overdose on medicine would be: 药物过量 (Medicine Overdose)
  Overdose on cocaine would be: 毒品过量 (Poison Products Overdose)
  People in China do know that Medicine can be poisonous, but its usually not labeled with the term "Poison", since its only bad if its taken in large quantities, above what you are supposed to take.

Never hear about china’s silver requirement though
- What's China's silver requirement?
  
  Europe didn't have much in raw materials that China wanted and China wouldn't trade for manufactured goods. So, most trade with China involved silver or gold. In an effort to address this trade imbalance, the British started shipping opium as a way to have another trade good for Chinese export.
  
  This documentary is part of larger series with both chinese and western historians, and goes into detail and background leading up to the opium wars https://youtu.be/26AjcWuYfUE