This thread contains a link from acolon_5 to a non-Strassman paper which also mentions 0.4 mg/kg as a "standard" dose for IV. IV injection is extremely easy in theory
--so there's no harm in starting smaller and working up until you find the right dosing for you. Two suggestions:
1) Use extremely pure spice. See
my new thread (from MIT, no less) for good videos of recrystalizations.
2) If possible, mix your spice in distilled water, and then add to normal saline--in an effort to approximate an osmotically sensible concentration. If you're having a doc assist you, he should have a reasonable outlook regarding that.
Overall, you need to be careful because CERTAIN impurities might CLUMP or precipitate in blood--and you don't want clumps of stuff floating through your arteries. I suppose you could test this by drawing a small amount of your blood, adding some of your proposed injection contents to it, and seeing what happens. Your doc friend should have input on this issue, too. If you have a pH meter it wouldn't hurt to have a look at the pH of what you plan to inject.
Also, the main possible DANGER from overdosing on DMT is a rise in heart rate and blood pressure. If you really want to do this carefully and cautiously you might want your doc friend to monitor your pulse and BP after your injections. If you REALLY want to cover all bases you could have the calcium channel blocker drug "Procardia" around--which would be helpful in the case of an overdose.
If you find a breakthrough dose, and it doesn't show extreme pulse and BP effects, then you've found the "holy grail" and I'd appreciate knowing the details
[OK, just to be sure there's no confusion on the math: If the average guy was about 70 Kg (154 lbs), and he wanted to use a dosage of 0.4 mg/Kg,
then he would dissolve 28 milligrams of pure spice into his injection]