A few ideas to add to this discussion:
LD50 values for opioids are generally useless information. Tolerance causes an inexact shift upward in the LD50 value for every individual. Unless someone is completely opiate naive - never used opiates before - LD50 values are a poor indicator of a lethal dose.
Keep in mind what LD50 means, the source of the LD50 information, and the species for which it is reported (rat, dog, human...) LD50 is the amount of drug that is lethal to 50% of the subjects given the stated dosage, the other 50% would survive, but in what condition? LD50s are usually expressed as an amount (mgs) per body weight (Kgs); careful math must be used to calculate the LD50 for a given individual, for the Americans out there: 2.2 pounds is equal to 1.0 Kg. Know and trust the source of your LD50 information. There are many shady, outdated sources for this difficult to establish data. Often people find LD50 numbers, which may have been experimentally determined for a laboratory animal, and use it for their calculations. They take this number, assuming it is directly applicable to humans, which it IS NOT, and use it to make dosage calculations. This could easily lead to the erroneous calculation of a safe dosage. However, when they take the calculated amount, which was based on experimental data gathered from pigs, they wind up dead and wonder why.
The idea that "junkies" - myself having been one for a good spell - OD often and die is a concept that needs to be better understood. Here is what I would add to people's knowledge to assit them in better understanding the tragedy of overdosing:
Long-term, current addicts who use only well prepared opioids (no active or harmful cuts, etc....) rarely die from ODs. This is a well-known fact in the addiction medicine medical community. I can provide references should anyone wish to verify this statement independently.
When taking 2, 3, even 4 times your regular, consistent dose it is most likely to become fatal when one or more of the following are true:
1. You are not a regular user of opioids; you are a chipper or a newbie.
2. You have used any other drug that day, especially alcohol, benzos or barbs.
3. You have taken a significant break from your regular, consistent using pattern, long enough that you are well past withdrawal symptoms.
4. You change methods of administration, e.g. from snorting to IV-ing or plugging.
5. You are unfortunate and/or misjudged your tolerance such that 2x your normal dose kills you despite none of the above being true. This is the "catch all", the gotcha clause, that exists to demonstrate that on occasion even the tolerant die from a 2x dosage of their OOC (opioid of choice) - but this is the exceptional case, it is very rare.
No one can predict what dose will kill someone. The person who can best estimate the lethal dose for someone is himself/herself, provided they have knowledge about how opiates affect the body and have a solid grip on the necessary info about their own usage such as the amount of their regular dose, whether or not they are chippers and do or do not have tolerance or if they are physically dependent.
It is surprising how many regular opiate users don't even know this much about their own use. You can ask many an addict their normal dose of heroin or oxycodone three times in a week and often get three wildly different answers. This isn't to say all, or even most addicts are this clueless, many addicts are very knowledgable about opioids, their use and their limits.
Know your body, know your habit, know your LIMITS! Then do not push them, if not for your own sake, for those who care about you.
