PGP and early-onset autosomal dominant Alzheimer disease: Although TRT variability of [18F]MC225 VT in humans is relatively high, under pathophysiological conditions, changes in P-gp function usually are larger, including a nearly 50% reduction in P-gp activity in mild Alzheimer’s disease and a 40% increase in P-gp protein levels in patients with epilepsy [32, 33].