buy stromectol canada 84, 85 MASAld is converted either by spontaneous decarboxylation to acetaldehyde, which is further oxidised into acetate through an aldehyde deshydrogenase catalysis requiring nicotinamide adenine dinucleotide NAD in its oxidised form NAD, or enzymatically to ?? hydroxypropanoic acid HOCH 2 CH 2 COOH by propionate deshydrogenase, which needs NAD in its reduced form NADH