Table 2.
Estimation of fecal drug concentration. Putative fecal concentrations of the four drugs were calculated by using reported fecal excretion rates. In case only urinary excretion has been investigated, remaining percentage was assumed to be excreted by the gastrointestinal tract. Available ratios of unchanged drug excretion were also taken into account to calculate minimally amounts (low). (nr: not reported; information taken from [26,27,28] and Novartis drug information; https://www.drugs.com/ppa). (BChE: Butyrylcholine esterase).
| Reported Parameters | Donepezil | Rivastigmine | Galantamine | Memantine |
|---|---|---|---|---|
| Plasma concentration [ng/mL] | 29.38 | 8.7 (oral) 21.6 (patch) |
83.7 | 179.3 |
| IC50 [ng/mL] | 2.55 (AChE) | 1.04 (AChE) 9.25 (BChE) |
1.62 (AChE/BChE) |
97 (NMDAR) |
| Urinary excretion | 57%; 17% as unchanged drug | 97% as metabolites | 60–93% | 74%; 48% as unchanged drug |
| Fecal/ intestinal excretion | 15% | less than 1% | nr | nr |
| Deduced dosages for the following experiments [ng/mL] | 1.3 (low) 4.5 (high) |
0.2 (low) 0.9 (high) |
5.9 (low) 33.5 (high) |
22.4 (low) 46.6 (high) |