The route originally used by Dr Costantini to administer thiamine (B1) was the intramuscular route (Costantini, 2013) (The Scientific Evidence). That route has the advantage of thiamine’s bypassing intestinal absorption and being absorbed quickly and fully. On the other hand, it has the disadvantage of requiring some assistance for the injections; it needs a prescription from a physician. There is a small risk of anaphylaxis with parenteral thiamine, with repeated injections (Wrenn, 1989; Morinville, 1998; Costantini, HDT website). This risk has been found to be mostly associated with intravenous administration (EFSA, 2006). To be safe, parenteral administration should be performed in facilities equipped to treat anaphylaxis promptly. Thiamine by i.m. was the only formulation available in Italy when Dr Costantini started using thiamine in PwP and was the route used in previous PD case reports (Luong, 2012).