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Doloxene, Depronal) taken in tandem with Oxazepam (see Nitschke and Stewart1), although Propoxyphene has already been withdrawn in the USA, Canada, UK, EU and New Zealand, and will become unavailable in Australia during 2012.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.