I don't know. The original dose for the FDA-approved application is 50 mg, so you are taking less than a tenth of that.
I have heard someone say it is better to start off at 4.5 mg rather than work your way up, and others say start at 2 mg. Some don't do so well at 4.5 mg but say they do great at 3 mg. Problem with LDN is that a lot of people have opinions, but few (if anyone) really know what the best dosages are.
I don't know how 4.5 mg was derived. Seems that the dosage should be related to weight, and why not 4 mg or 5 mg? I guess a doctor somewhere decided that 4.5 mg was the ideal dosage, but I don't think there were any scientific studies to show what the ideal dosage for MS patients actually is.
If you have 4.5 mg pills, I guess give it a try and see what happens. Let us know. I started off at 2 mg and am working up slowly, getting to 3 mg. No problems so far that I can tell, but some dreams are a bit more vivid and interesting than normal. No nightmares, just wierd things.