Although "just say no" is certainly the safest position to take on recreational drug use, the vast majority of humans ignore this advice. Some use alcohol, nicotine or caffeine; others take prescription medicines in ways other than as prescribed; others use illegal drugs like marijuana, cocaine and heroin. Add that all up and a significant majority of the population is "under the influence" at any given time.
Consequently, we owe it to ourselves to understand the risks involved with using these drugs. To avoid the kind of accidental overdose that seems to have killed Heath Ledger, we need to understand several important facts.
First, if I could only impart one lesson about reducing overdose risk, it would be this: Don't Mix Drugs-- but Especially, Don't Mix Downs. That is, don't take "depressant" drugs-- drugs that make you calm or sleepy, not depressed!!!-- in combination with each other. This category includes sleeping pills. These include benzodiazepines like Xanax, Valium and Clonopin--chemical names for this class of drugs tend to end in -zepam. So, valium is diazepam, etc.
The category also includes benzodiazepine-like drugs such as Ambien and Sonata as well as drugs like barbiturates which are rarely prescribed these days.
Another category of depressant drugs is opioids: These include heroin, Oxycontin, Vicodin, codeine and similar painkillers. Antihistamines like Sominex and Unisom are also depressants.
The most commonly used depressant drug is alcohol, however. Mixing drugs across these categories is the riskiest type of drug use there is, especially if some of them are injected. The overwhelming majority of overdose deaths result from mixtures of depressants: for example, most of the "Oxycontin" deaths that have been reported recently are more accurately described as Oxycontin-plus-alcohol-and/or-benzodiazepine.
About 75% of all overdose deaths involve drug combinations: the most deadly combinations seem to involve opioids plus other depressants. According to the federal Drug Abuse Warning Network, more overdose deaths are caused by opioid mixtures than by any other single drug or combination of drugs [PDF].
Cocaine use is reported in a significant minority of overdose deaths: however, because cocaine counteracts some of the sedating effects of depressants, it may actually reduce overdose risk [PDF] from opioids. Nonetheless, cocaine/depressant combinations--especially intravenously-- are still highly risky.
Heath Ledger appears to have been one of the less-common cases in which a mixture of benzodiazepines, benzodiazepine-like drugs and antihistamines was fatal.
His case may also be an example of the second key fact I'd love to impart in sane risk-reduction education: if you have been addicted, and then quit, the dose you can tolerate after detox is far lower than the dose you could tolerate before.
This means you can literally overdose on an amount of drugs that previously would not even have been enough to get you high.
While relapsing is obviously not advised, if someone insists on doing it, he should be aware of this fact and be very cautious about doses taken. There are actually addicts who go into detox deliberately seeking this effect: they know their habits will be a lot cheaper, at least at first, after a period of abstinence.
Failing to take tolerance into account can be deadly, however: a large percentage of overdoses occur amongst recently detoxed addicts.
Obviously, we'd prefer no one to ever overdose and no one to ever relapse: but since relapse is a frequent occurrence in addiction, I'm sure everyone who knew and loved Heath Ledger--and all of his fans--would prefer that he had known these facts, if, indeed, his death was not a deliberate suicide.
I'll post soon about how to save lives in the crucial time following an overdose