this was posted at the h!^e so i though i would shed some light here...

here's an excerpt of something from rhodium about isomerising ephedrine/pseudoephedrine

On heating ephedrine hydrochloride with 5% hydrochloric acid, under pressure, at 170-180°C (248) or with 25% acid, at 100°C, the compound is partially converted to pseudo-ephedrine (20, 32, 40). The conversion is reversible and an equilibrium is established. According to Emde (39), the rearrangement takes place by replacement of the hydroxyl group by chlorine, followed by hydrolysis. Oxidation of ephedrine or pseudo-ephedrine, gives benzaldehyde or benzoic acid.

so you can get 50% ephedrine out of pseudo if you think it's worth it