I will usually take my methadone doses orally (65% of the time), but I rather enjoy doing intranasally. I tried it after reading all the negative reviews months and months ago, and noticed the typical annoying irritation of the roxanne methadone tablets like everyone else. However, I did notice a some differences in onset. My nose isn't in the best condition after years of snorting various substances I will say, with ketamine imo being one of the likely suspects to have caused the most damage to it, but speculation (not hating on k, it just seems to cause more bleeding, discomfort than other substances). So because of trying to maximize the amount of the drug actually being able to be absorbed, I tried a CWE in a 5-mL oral syringe, then transfered the solution with as little of the solids into a 50-ml erlenmeyer flask. I then used a 1-mL oral syringe for nasal administration trying to pull up as little solids . I squirt .10-.20 mL of solution into each of my nasal passages every couple mins (till they feel primarily dry), and repeat. I usually nasally dose when I have very few methadone and need trying to avoid WDs, or after I've taken oral doses for a higher dose of methadone. With this method I find that the methadone starts to effect me around 3-5 mins after getting atleast 25% of the solution (10mg total solution for example) absorbed. I will reach the peak probably around 30mins, but potentially could be alot less if I would snort it faster (I get distracted) - the tmax in the study I post below have results of 0.12h (+/-0.07-0.177). The BA from my experience seems as high, if not higher than oral at times (sometimes oral can very, juts like studies show). I also found it's primary high effect to last maybe 2 hours shorter than orally, but it's pretty much the same.
I just recently decided to create a little filter apparatus to transfer the solution of methadone into the flask with a lot less solid material and noticed an increase in the speed of the come up, as well as a lot less irritation. It was no worse than snorting powdered k, once the solution is filtered through the bit of coffee filter and cotton ball. Also using a 1-mL syringe it a must. You want to only snort .10-.20 mL max if you want majority of it to be absorbed orally.
Heres a study supporting all of this nasal administration being similar to intravenously (a good alternative to IV), and no negative aspects against oral consumption. The only problem would be if you are trying to consume large quantities of methadone. Since the tablets only come in 5 and 10mg, there is a lot of binder and filler. I have roxanne 5mg tablets and for 10mg, I'll use around 2mL. In the study below they have 50mg/mL, so you could reduce it and ingest large amounts in a relatively short period of time.
http://paincenter.wustl.edu/c/BasicResearch/documents/ClinPharm2002.pdf
So if this study is correct, I might dose my 5mg QID using this method. Or at least for my last dose before bed. It honestly gives me as good of a rush as oxycodone insufflated, but it comes down to a steady concentration in 20-40mins, so i can honestly say it does give a rush.
Give it a try, especially if you have a micron filter or even make a ghetto one. There is not much of a burn to notice, just a little tingling that disappears in less than a min.