The human pharmacokinetics of oral ingestion of glucosamine and chondroitin sulfate taken separately or in combination

Jackson CG, Plaas AH, Sandy JD, Hua C, Kim-Rolands S, Barnhill JG, Harris CL, Clegg DO · Osteoarthritis and Cartilage

Reaches the opposite conclusion to Volpi's studies. Endogenous plasma chondroitin sulfate ran at about 20 ug/mL with no diurnal swing, and neither a single 1200 mg dose nor three months of daily dosing changed its concentration, chain size or disaccharide composition: the 6-sulfated disaccharide, about 45% of the dosed material and under 10% of the endogenous pool, did not rise at any time point to 36 hours. Glucosamine was undetectable before dosing and reached a Cmax of 492 ng/mL alone against 311 ng/mL taken with chondroitin (P<0.05); after three months of combined dosing its AUC was 1,099 against 1,870 ng.h/mL for glucosamine alone. The authors conclude that ingested chondroitin does not detectably reach the circulation intact, that any effect would come from breakdown products or from actions in the gut lining or liver, and that co-dosing lowers rather than raises glucosamine exposure.

Population

Three phases in the NIH GAIT programme: 14 undosed adults for baseline plasma levels, 29 healthy adults randomised to a single dose of glucosamine HCl 1500 mg, chondroitin sulfate 1200 mg or both, and 28 adults over 40 with symptomatic knee pain dosed after three months of daily glucosamine, chondroitin or both

Intervention

Oral glucosamine and chondroitin sulfate, alone and combined

Comparator

Between dosing groups (each agent alone against the combination), with the 14 undosed subjects for baseline levels

Limitations

Pharmacokinetics with no clinical endpoint. The authors note their total-chondroitin assay could not resolve a 200 ng/mL change against a 20 ug/mL baseline that drifts by about 5 ug/mL through the day; the compositional argument, no rise in the 6-sulfated disaccharide, is the stronger half. Groups of 8 to 11 per regimen. Funded by an NIH NCCAM R21 grant and the National Arthritis Foundation, no conflicts declared, and the group is the GAIT investigators, independent of the chondroitin manufacturers. Read as the NIH author manuscript.