Small Amounts

This is arsenic trioxide.  Commonly known as just arsenic.

https://upload.wikimedia.org/wikipedia/commons/a/a7/Arsenic_trioxide.jpg

It's cheap and readily available.

Arsenic is sometimes used to cut cocaine because it's texture is extremely similar to cocaine powder.

Arsenic is extremely poisonous

SMALL amounts of Arsenic are REQUIRED for normal operation of the body. However, larger doses can be fatal. An ACUTE FATAL DOSE of Arsenic is in the range of 2-20mg/kg body weight/day. Thus, a relatively healthy person who weight 160lbs, about 72.6kg, may die if he ingests between 0.145gm and 1.45gm Arsenic in the form of Arsenic Trioxide, As₂O₃. i.e. 0.192gm to 1.92gm of Arsenic Trioxide. (Arsenic Trioxide is probably the most commonly available Arsenic compound). Considering the high density of the oxide, less than 1/8 of a tea spoon can be fatal. Smaller amounts may be fatal if unhealthy people, elderly or children are exposed. The symptoms of poisoning by SMALL amounts of Arsenic are not always distinguishable from symptoms of other afflictions.

The reason that arsenic is sometimes used to cut cocaine is because cocaine is illegal.

If you find arsenic in your aspirin, you can sue Bayer.

Where's your recourse for finding it in your cocaine?

 There's reasons that many people advocate the legalization of drugs that have nothing to do with being unconcerned about people dying from overdose and misuse.

The two main factors for me are both related to the behavior of the criminals who make, import and distribute the products that are banned.

As above, they can mess with the quality of the product in dangerous ways to stretch the amount of actual product being being sold.  You can sue Winn-Dixie for selling you a dozen eggs and only getting 9 and three ping-pong balls.  You can't sue MS13 if they sell you a kilo of Similac and tell you it's coke.

Then there's all the outright murdering.

One reason Americans are getting willing to try legalization is the fact that we've done this before.  We banned alcohol.  The ban had almost no effect on the supply of liquor available to consumers.  But it did cause the prices to go up and smuggling liquor became lucrative enough to murder someone over sales territory.

People died from methanol being substituted for ethanol.  People died from poisons being substituted for the actual booze they thought they were buying.  People died from drinking booze which was tainted by unsafe manufacturing processes.  People died from unsafe practices in the production of alcohol, including fires and explosions.  Does any of this sound familiar yet?

Eventually it was relegalized.

And the murders stopped.  And the quality improved.  And people still drank themselves to death, just like before and during Prohibition.  The ban had no positive effect on the people who were most at risk of the dangers of alcohol.

Legalizing alcohol did have positive effects on the crime rate.  To put it in perspective:  When was the last time you heard about Total Wine shooting up an ABC Liquor?  Or a B21 hijacking a shipment destined to a bar?

We pretend that drugs are somehow different from booze.

The physical amounts needed to get euphoric are smaller is all, but there was once a time when drugs were legal and over the counter.  Ever hear of laudanum?

Legalizing drugs won't keep people from dying from overdoses.  But it's likely going to save many lives from murder and poisoning.  If, say, cocaine or morphine were readily available and cheap, would people be seeking stronger opiates which are easier to OD on?

But never forget, though, by banning these things you are NOT saving the users.  No prohibition on sinful things has ever saved the people addicted to it, and those bans always make it worse.