Cytotoxicity of individual and dual-drug ChEI combinations to SH-SY5Y cells: Human neuroblastoma cells were incubated with donepezil (Don), tacrine (Tac), berberine (Ber), and galantamine (Gal) or dual-drug combinations: BerTac (berberine and tacrine), BerGal (berberine and galantamine), TacDon (tacrine and donepezil), DonGal (donepezil and galantamine), DonBer (donepezil and berberine), and TacGal (tacrine and galantamine), and cell viability quantified using a MTT assay. Significant changes were quantified using a one-way ANOVA. ns = non-significant effect on cell viability. All other histograms not marked with ns, displayed significant changes from controls.