The responses of 11 parkinsonian patients were evaluated by three standard laboratory pain-inducing techniques involving radiant heat, cold pressor, and electrical stimulation, before and during therapy with levodopa. All techniques measured three pain-response parameters—pain threshold, pain tolerance, and pain sensitivity range. The patients' psychological ability to endure pain was not significantly altered, and no consistent changes were observed with cold pressor and electrical stimulation. However, the highly significant correlations found between levodopa dosage and the increases in radiant heat pain threshold and pain tolerance (P <.01) suggest that patients became less sensitive to heat stimulation while taking levodopa.
Battista AF, Wolff BB. Levodopa and Induced-Pain ResponseA Study of Patients With Parkinsonian and Pain Syndromes. Arch Intern Med. 1973;132(1):70-74. doi:10.1001/archinte.1973.03650070062009