Stability of phenylpropanolamine hydrochloride in liquid formulations containing sugars

Stability studies with a decongestant syrup formulation containing phenylpropanolamine hydrochloride in a sugar vehicle indicated a loss of phenylpropanolamine hydrochloride. To ascertain the biological significance of this indicated chemical loss, the degraded formulation was administered to human volunteers and the urinary excretion of phenylpropanolamine hydrochloride was determined. The excretion and chemical assay patterns were in good agreement, indicating that the sugar vehicle was both chemically and biologically incompatible with phenlypropanolamine hydrochloride. A control formulation made with phenylpropanolamine hydrochloride in a sorbitol vehicle showed good chemical stability and urinary excretion patterns. Further studies showed chemical losses with phenylpropanolamine hydrochloride in the presence of fructose, dextrose, and 5-(hydroxymethyl)-2-furaldehyde but not with levulinic acid. Possible mechanisms for the sugar-phenylpropanolamine hydrochloride interaction are discussed.