Objectives: The pharmacokinetics of free L-dopa in blood and tissue of five parkinsonian patients with malignant melanoma was studied with microdialysis. In one case the effect of L-dopa treatment on 5-S-cysteinyldopa and the melanoma was studied. Gastric emptying and its effects on free L-dopa in blood were also investigated in one of the patients.
Methods: Five patients were given 100 mg L-dopa with 25 mg benserazide. Blood and dialysates from the circulation and fatty tissue were collected for analysis. [13C]-Octanoic breath test was used for analyzing gastric half-emptying time.
Results: Four of the patients had similar pharmacokinetic patterns for L-dopa and a significant (P < 0.05) increase of serum 5-S-cysteinyldopa occurring 30 min after L-dopa intake. Delayed L-dopa peaks and slow gastric half-emptying time were found in 1 patient. A dose-dependent increase of 5-S-cysteinyldopa occurred but no melanoma metastases were seen during long-term L-dopa therapy.
Conclusion: L-dopa therapy increases 5-S-cysteinyldopa levels but does not seem to cause progress of melanomas. Gastric emptying impacts L-dopa pharmacokinetics.