Comparison of pain models to detect opioid-induced hyperalgesia

Figures & data

Figure 1 Comparison of pain threshold and pain tolerance between control subjects (n = 16), methadone dependent subjects (n = 8), and buprenorphine dependent subjects (n = 8) among the four different pain modalities. (A–D) depict cold pain threshold, cold pain tolerance, ischemic pain threshold, and ischemic pain tolerance, respectively, using Kaplan–Meier survival curves. (E and F) represent the electrical stimulation threshold and tolerance and the mechanical pain threshold and tolerance, presented as the mean ± standard deviation.

Abbreviations: Meth, methadone-dependent subjects; Bup, buprenorphine-dependent subjects; C-TR, controls’ threshold; M-TR, methadone-dependent subjects’ threshold; B-TR, buprenorphine-dependent subjects’ threshold; C-TL, controls tolerance; M-TL, methadone-dependent subjects’ tolerance; B-TL, buprenorphine-dependent subjects’ tolerance.

Table 1 Correlations between models

	Cold threshold	Cold tolerance	Ischemic threshold	Ischemic tolerance	Mechanical threshold	Mechanical tolerance	Electrical threshold	Electrical tolerance
Spearman correlation coefficients (n= 32)
Cold threshold	1.00	0.58	0.11	0.09	0.37	0.22	0.07	−0.10
		0.0005	0.53	0.62	0.04	0.22	0.72	0.60
Cold tolerance	0.58	1.00	0.46	0.50	0.31	0.38	−0.25	0.18
	0.0005		0.009	0.003	0.09	0.03	0.16	0.33
Ischemic threshold	0.11	0.46	1.00	0.57	−0.02	0.21	−0.25	0.16
	0.53	0.009		0.0006	0.93	0.25	0.16	0.39
Ischemic tolerance	0.09	0.50	0.57	1.00	0.19	0.34	−0.22	0.19
	0.62	0.003	0.0006		0.30	0.05	0.22	0.30
Mechanical threshold	0.37	0.31	−0.016	0.19	1.00	0.80	0.28	0.43
	0.038	0.09	0.93	0.30		<0.0001	0.11	0.01
Mechanical tolerance	0.23	0.38	0.21	0.34	0.80	1.00	0.21	0.52
	0.22	0.03	0.25	0.05	<0.0001		0.25	0.002
Electrical threshold	0.066	−0.25	−0.25	−0.22	0.28	0.21	1.00	0.56
	0.72	0.16	0.16	0.22	0.11	0.25		0.0009
Electrical tolerance	−0.098	0.18	0.16	0.19	0.43	0.52	0.56	1.00
	0.60	0.33	0.39	0.30	0.01	0.002	0.0009

Note: In each cell, the upper figure is the Spearman rho and the lower figure the P value.