Table 6.

Prevalence of Detected Lesions by Microscopic Analysis in 28 Rhesus Macaque Monkeys after Receiving Methylphenidate for Five Years, by Dosage Group.

Methylphenidate Dosage (mg/kg, bid)
	Control group (0) n=9	Low-dose group (2.5) n=9	High-dose group (12.5) n=10
Lesion	Prevalence, %	Prevalence, %	Prevalence, %	P
Myelin figure/body in the sarcoplasm	100	100	90	NE
Membrane accumulation in the sarcoplasm	100	89	80	0.75
Edema in the sarcoplasm	78	78	70	0.90
Dilution of the sarcoplasmic reticulum	89	89	80	0.81
Increased lipid droplets	33	33	40	0.94
Lipofuscin bodies	78	78	90	0.70
Hypercomplex folding in the nucleus	0	11	10	NE
Myelin figures in the extracellular space	56	33	40	0.71
Mitochondria in the extracellular space	44	44	60	0.79
Cellular infiltration of mononuclear cell, focal**	33	33	10	0.48
Necrosis, focal**	11	0	0	NE

NE, not estimatable. Unless otherwise noted, all data are from transmission electron microscopy.

Prevalence was 100% across all dosage groups for degenerative mitochondria, myelin figure mitochondria, increased mitochondria, and dysmorphic mitochondria. Probability values for statistical differences in percentages between dosage groups were calculated with exact permutation tests.

^*Type I error rate (α) =0.01.

^**Light microscopy