I think in this sense, microdosing pharma would be an ideal solution. A high dose would have too many intense ups and downs to work and could push the person beyond the brink. However a low dose results in a lot more fluidity and a balancing effect, it's an intensely meditative state. A threshold dose every day or two for a few weeks should clear out the demons methinks. In fact the harmala alkaloids on their own, in the right dosage, are more than good enough for this.

They are discovering genetic markers for suicidal ideation or S/I for short.
http://psychiatry.jwatch.../content/full/2008/107/1
There is a biological basis for S/I and more evidence for that all the time. In the case of depression and not say a personality disorder your neurochemistry is really off. People often say it's their choice. But isn't when after a suicidal intervention with the right medication can cause some one to come out of it. Then there is also the fact that some clients when given certain medications get an increase of S/I. What does this point to other then anrelationship between neurochemistry and S/I.
I believe your playing with fire though giving any one with S/I a hallucinogen. I know a guy in he amazon that gutted himself like a fish right after an ayahusca ceremony. I think that the harmalas alone however in non-hallucinogenic levels could be valuable at first. Maybe...
I would rather give them the right level of antidepressent then a hallucinogen. Though some people have smoked Changa while suicidal and it shifted them right out of it...'so who the fuck knows..

Depression is really a problem that starts on the energetic level. I have tendencies towards Depression sometimes.
However a proper hit of DMT has revealed to me the origin of many of my psycho-spiritual problems and thereby healed/corrected it.
Depression and the Suicidal thoughts that flow out of it are areas of disfunction; of no consciousness. All it needs to dissolve is the Light of Comscioussness.
Usually we don't dare look at those spiritual sores. DMT forces us to look at them and if you're not affraid and give them your fullest attention they will dissolve.

In that sense it is much more effective as a classical anti-depressant, because it solves the problem at the core whereas the commonly prescribed anti-depressants only temporarily surpress the symptoms at the surface. The first actually solves the problem, while the second burries it till it becomes pressurised and one day "erupts" outwards leading to suicide or violence.

I bet that a few DMT-vapor sessions guided by a Therapist turns out to be alot more effective at Curing depression than conventional anti-depressants and therapies are.
Now I hope Strassman and friends could research that area, allthough it seems very slippery terrain.

being bi-polar (doesnt use medication) SWIM finds that sub-breakthrough doses of dmt seems hit a "reset" button when in a depressed episode. Usually SWIM ends up seeing how pointless depression/suicidal thoughts are and can see life from a bigger picture and is brought back to a "normal" state after the comedown. This is what SWIM has noticed from several occasions anyways, and never risked a full on breakthrough, not sure how that would pan out..

I definitely wouldn't try and convince someone who was suicidal to try DMT but if they wanted to try it of their own accord and with a healthy intention, I'd not try and and dissuade them -- I would give them as much emotional support as I could. I believe that the best form of healing comes from within, which is why it is important to let people do things because they want to -- for their own reasons.
I eschew the notion that there is ever a last resort with suicide. When it seems like this is the last chance, that's a good time to start talking. It's not like they're destined to off themselves at exactly 6pm unless DMT is administered post haste.

//somewhat related anecdote with themes of drugs and suicide
Last year, I ran into a friend at a festival. He was tripping with this girl. They had both eaten a bunch of xtacy and were trying to get all the passer-bys to hug them. I got to talking with them for a while. The girl kept laughing in a totally demented way. She had recently gotten out of prison and was now living with her abusive family. She kept talking about how she was going to kill herself. How she hated the thought of coming down off the drugs because when she did, she would no longer feel anything. I asked her if she wouldn't feel awful tomorrow from the hangover and she said that she probably would. "See, you'll still feel something," I replied. This caused a big smile on her face. She seemed to relax a bit.
I haven't seen either of them since then. My friend was supposed to help her get into a youth shelter so that she could escape her situation at home. I hope she didn't off herself, she was really pretty and strong -- like coiled steel. Hardly anyone ever comes close to matching me in physical strength but this girl could nearly over power me. She said it's because she had to be tough in prison.

I know I'm not qualified to give medical advice and have done my best to only share my thoughts and experiences on the matter.
It's an interesting discussion. I hope it is helpful to everyone.