Bioavailability of D-penicillamine in relation to gastrointestinal involvement of generalized scleroderma

The bioavailability of D-penicillamine was measured in 24 patients with generalized scleroderma (Progressive Systemic Sclerosis, PSS). Esophageal changes characteristic of generalized scleroderma were present in 15 of the patients, and 3 of those patients had duodenal involvements as well. The plasma concentrations of D-penicillamine were measured at 0 h, 1 h, 2 h, and 4 h after an oral dose of 300 mg D-penicillamine. Patients with duodenal and/or esophageal changes specific for scleroderma had significantly lower bioavailability of D-penicillamine than scleroderma patients without gastrointestinal manifestations. The decreased plasma D-penicillamine in scleroderma patients with involvement of the gastrointestinal tract may be due to an increased degradation of D-penicillamine in the gastrointestinal tract and/or an impaired absorption of the drug. Since the plasma level of D-penicillamine is so sensitive to pathological changes of the gastrointestinal tract, it may be advisable to adjust the dose of D-penicillamine on the basis of measurements of the plasma concentration of D-penicillamine.