In the UK, data from the Office for National Statistics for 2001 (see England & Wales methods of suicide) showed that of the total 1,243 drug related suicides, 28.5% were due to paracetamol and its compounds, and 24.5% were by anti-depressants, making these the top two methods.
In the US (see Drug poisoning in the US), the story is similar, with the CDC reporting that the most commonly used drugs identified in drug-related suicides were psychoactive drugs, such as sedatives and antidepressants, followed by opiates and prescription pain medications.
The UK Office of National Statistics also publishes data on all deaths from poisoning (i.e. intentional and unintentional death). In that table (see Drug poisoning in England & Wales), class A drugs like heroin/morphine, methadone and cocaine come highest, followed by paracetamol, anti-depressants and insomnia medications. The data from the US (see Drug poisoning in the US) also features a similar top four.
So the statistics give a clear indication of which drugs can be used to achieve a drug induced death, although they don't actually show, by method, what the percentage success rate of each method is. If the overall ratio of success with a drug induced suicide is 40 to 1 against, it is probably likely that even the drugs that appear highest on the table still have a fair number of unsuccessful attempts.
A common drug used in attempted suicides is sleeping tablets of various forms. Decades ago, when barbiturates were prescribed for sleep issues, it was possible to overdose on them. Modern sleeping tablets are not, by themselves, lethal, and taking a large dose as a suicide attempt is more likely to result in a long sleep and a trip to the hospital emergency department than death.
What does not appear high on the list of drug related deaths is barbiturates. Although a number of barbiturates are highly lethal, the reason they don't appear highly on the tables of drug related deaths is that they are now rarely prescribed, and extremely difficult to obtain without a prescription.
Literature and websites most commonly cite Seconal (Secobarbital) and Nembutal (Pentobarbital) as the two most effective barbiturates for a swift, painless and swift death. The suicide holy grail. Seconal is a strong sedative that is used to treat severe, long-standing insomnia in people already taking barbiturates. Reportedly this drug is not even available on prescription in the UK anymore, although it may well be in other countries, including the USA.
Other effective drugs include:
Propoxyphene (commonly sold as Darvon, Doloxene, Depronal) taken in tandem with Oxazepam (see Nitschke and Stewart1), although Propoxyphene has already been withdrawn in the USA, Canada, UK, EU and New Zealand, and will become unavailable in Australia during 2012.
Amitriptyline is a tricyclic anti-depressant that can also be very effective when combined with a sleeping medication like Oxazepam. It is important to take anti sickness drugs with this method as the drugs taste very bitter (see Things to consider). Or else try and put them into empty 1gm gelatine capsules if they can be obtained. Opinions on minimum lethal doses for this method differ, with Nitschke and Stewart1, stating 5 grams, and the ASH website2 stating 7-8 grams depending on weight. ASH2 also recommend a cocktail of drugs that includes Cimetidine and Midazolam. Full information on quantities is on their website. It should be noted that death using this method takes between 12 and 24 hours, which does not make it the quickest method, although death is said to be peaceful.
The length of time to death makes not being interrupted quite crucial, meaning other methods are probably better. There is a report and discussion on The Peaceful Pill Handbook forum following someone getting numbness and burning in their mouth whilst trying to ingest a lethal dose of Amitriptyline, although the response from the expert was that not everyone would get this reaction. Beware though, as ingesting high but non-lethal quantities of drugs is likely to cause harm.
Phenobarb (see http://en.wikipedia.org/wiki/Phenobarbital) is also cited to be lethal, but can take several hours to be effective, so use in combination with a drug that induces sleep is sensible. Nitschke and Stewart1 do mention this method, although it is not widely commented on as a popular suicide method.
Nembutal is currently the drug of choice for human euthanasia in countries where that is legal, making it an unsurprising choice for people wishing to end their own lives in other countries. Given it is highly effective, its use is tightly controlled, and thus it is extremely difficult to get hold of at all, and almost impossible to obtain legally. One of the reasons why many people resort to less effective drugs.
Nembutal's FDA approved human uses include treatment of seizures and preoperative (and other) sedation. It is used by vets as an anaesthetic, and for animal euthanasia.
Nembutal is generally obtained in liquid form, but is difficult to obtain from any place in the US, Canada, Europe or Australia. In the Peaceful Pill Handbook1, Nitschke and Stewart have a long section about how to obtain this drug, mainly centred around purchasing it in person from vets in Mexico, Peru, Bolivia and Thailand (although noting that taking it out of any of those countries is illegal, as is posting it back to your home country). Prices are much cheaper than mail order.
There are reports from people who have successfully obtained the drug, and from those that haven't. Towards the end of 2011 it seemed it was increasingly difficult to obtain the drug over-the-counter in Mexico, although by no means impossible with persistence. In 2012 Peru seemed the country of choice for obtaining over-the-counter Nembutal.
They also mention a source in Mexico which has had generally positive feedback, where veterinary Nembutal can be purchased over the internet (for around US $450), although 10-15% of deliveries are said to be intercepted by customs.
It is also possible to obtain very pure powered Nembutal from China via a number of mail order sources. It is generally sold in quantities sufficient for two people at around US $1,000, and simply needs dissolving in water to be used.
It is best to check the latest version of the Peaceful Pill ebook and forum1 for current information before attempting to purchase from any source (although see the notes to Minimum lethal doses for information on lethal doses). Users on the forum often discuss most reliable sources to purchase this drug, and it is changing all the time. It is also worth noting that importing Nembutal into most countries is illegal, although Nitschke only cites one report of a person being prosecuted.
The information contained in the Peaceful Pill Handbook about Nembutal is regularly updated, and does include pictures of packaging. Anyone considering purchasing and using this drug would gain much information by purchasing the latest version of the ebook, as this is the most comprehensive source of up to date information about obtaining and using Nembutal.
Exit International (www.exitinternational.net), founded by Dr Nitschke, also offer a Nembutal testing kit, to check if the drug is (a) a barbiturate and (b) of sufficient strength to provide a peaceful death at the time of one's choosing. Given some people obtain Nembutal from uncertain sources, or store it for some time before use (it has a limited shelf life, although has been known to be stored for 15 years and still be fine), the kits were designed to reassure people that their Nembutal is still effective.
Derek Humphy's book Final Exit3 is also worthy of consideration for further information on drugs as a method of suicide. It is available as a book or ebook and periodically updated, although not as often as the Peaceful Pill Handbook.
Dr Phillip Nitschke with Dr Fiona Stewart, The Peaceful Pill eHandbook, revised November 2011, and forum and forum at www.peacefulpillhandbook.com/forum.
Alt Suicide Holiday website, http://ash2.wikkii.com/wiki/Amitriptyline_Cocktail.
D Humphry, Final Exit: The Practicalities of Self-Deliverance and Assisted Suicide for the Dying, 2002.