Double-blind evaluation of oral L-prolyl-Lleucyl-glycine amide in Parkinson's disease.

A 4-month double-blind study comparing the effect of increasing oral doses (up to 1.0 g daily) of synthetic L-proyl-L-leucyl-glycine amide (PLG) and placebo in 20 parkinsonian patients showed no significant improvement in objective scores of functional disability. However, important trends and some significant results were observed with the lower doses of PLG. These essentially negative results may be attributed to poor intestinal absorption of the compound, a short biologic half-life in the blood, or administration of oral doses that were much higher than required, or a combination of factors. In further studies with this peptide, which are encouraged, the intravenous route should be used until the question of intestinal absorption is resolved.