1litre is £1.29 at Morrisons as posted earlier in this thread.
Quote
does viagra work by increasing the NO produced?
It doesn’t. Nitric Oxide is involved in the production of cGMP, which aids erection. cGMP is removed by enzyme PDE-5 which facilitates loss of erection. It is the PDE-5 that Viagra inhibits fairly selectively, which allows the erection to be sustained. If you take something that helps Nitric Oxide (Arginine, PJ etc), then it is an additional aid to erection on the inflow side, whereas viagra helps limit outflow provided stimulation is maintained.