I looked at a comparable human trial for pediatric IBD which used a total daily dose of 3-6 grams administered three times daily at either 1 gram or 2 grams each time.
Of note was because of hepatic clearance, they had the patients swish the liquid around in their mouth for at least 1 minute before swallowing to get some mucosal absorption.
Only minute amounts are needed to have an effect, but the problem is getting it to where it needs to be given the way it is metabolized.
As far as how quickly an effect was observed in the human, in the pediatric study they comment on this for those who received the GlcNAc rectally, but don't have a similar summary for the speed of the response for those taking it orally.
Quote:
Of the five responders to GlcNAc monotherapy, one patient had a clinical response within 3 days of starting treatment with complete resolution of bleeding and discharge, two were asymptomatic or with minimal symptoms after 4 weeks and two responded more slowly, with clear improvement noted by 3 months.
Alimentary Pharmacology & Therapeutics
Volume 14, Issue 12, pages 1567–1579, December 2000
A pilot study of N-acetyl glucosamine, a nutritional substrate for glycosaminoglycan synthesis, in paediatric chronic inflammatory bowel disease
S. Salvatore1, R. Heuschkel1, S. Tomlin2, S. E. Davies3, S. Edwards4, J. A. Walker-Smith1, I. French5, S. H. Murch1