Thanks so much for all these responses! I actually checked back in just after
pofacedhoe wrote his/her first reply, and it was such an eye-opening point about the behavioural aspect of actually smoking, being a huge part of why I'm finding it so hard to quit, that I just needed to sit on that for a few days. The instantaneous resistance I felt to the idea of moving to oral intake was very telling indeed. I also do really like the suggestion by
tweex to combine them orally until I am able to taper down to just the modafinil. Good practical advice, thank you! There was a couple of studies I found in which mice were given modafinil and meth together, and whilst that in itself is not something I would base an assumption of safety on, there doesn't appear to have been any negative effects from the combination, but rather the modafinil was found to act protectively on a neural level. One such study is here:
Modafinil Abrogates Methamphetamine-Induced Neuroinflammation and Apoptotic Effects in the Mouse Striatum
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046599/
I also found multiple studies in which humans who were meth-dependent were given modafinil and then followed to see if this reduced the number of meth positive urine samples over a time period, and there didn't seem to be concern that anything horrible would happen if participants did take meth whilst also being on the modafinil. Links to a couple of them:
Randomized, double-blind, placebo-controlled trial of modafinil for the treatment of methamphetamine dependence
http://www.ncbi.nlm.nih.gov/pubmed/20092966/
Modafinil for the treatment of methamphetamine dependence
http://www.ncbi.nlm.nih.gov/pubmed/21840138/
In regards to the studies I mentioned in my first post, with modafinil being found to increase cognitive function specifically in areas where there was damage caused by meth use, here are links to some of those:
Effect of Modafinil on Learning and Task-Related Brain Activity in Methamphetamine-Dependent and Healthy Individuals
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3077264/
Modafinil restores methamphetamine induced object-in-place memory deficits in rats independent of glutamate N-methyl-d-aspartate receptor expression.
http://www.ncbi.nlm.nih.gov/pubmed/24120858/
Acute modafinil effects on attention and inhibitory control in methamphetamine-dependent humans.
http://www.ncbi.nlm.nih.gov/pubmed/22051208/
That last study there is quite interesting as well for its findings in regards to inhibitory control. What they found was that there was no significant difference for control participants on this measure, but there was for the meth-dependent participants (a positive effect). Another study which looked at modafinil and impulse control, but this time with alcoholics, found somewhat complimentary results with only those participants who had a poor baseline level of impulse control gaining benefit on this measure from taking modafinil. Concerningly, they did also find that it could actually have a detrimental effect on this measure for participants who had a higher baseline level of impulse control (although I don't believe his will be a relevant issue in my case):
Effects of modafinil on neural correlates of response inhibition in alcohol-dependent patients
http://www.sciencedirect.com/science/article/pii/S0006322312005872/
I think for me, the idea of something which will speed up the rate of recovery I can experience from the vast cognitive damage caused by my methamphetamine use, is very appealing. I feel extremely unmotivated to face going through withdrawals and cravings, and also have it take so long before the positive benefits of quitting start to kick in.
One of the other daunting issues for me personally, is avoiding weight gain whilst quitting. Despite that I have not lost weight from meth as it doesn't make me lose my appetite when I'm using it daily, I still get the huge appetite increase and food cravings when I try to stop! The second time I tried to quit and went up almost 2 dress sizes, really freaked me out. As petty an issue as it may seem to some, this is a serious issue which really contributes to my hesitation in stopping, despite how bad meth is!
Another of the studies involving humans taking modafinil whilst being required to return urine samples on a regular basis, which I don't think I linked above, did find that those meth-dependent participants who took modafinil had a significantly reduced level of weight gain:
A double-blind, placebo-controlled trial of modafinil (200 mg/day) for methamphetamine dependence
http://www.ncbi.nlm.nih.gov/pubmed/19149817/