There's Zantac/ranitidine discussion in the SN thread. It seems to be as effective as cimetidine, if not more. They are the same type of drug and act comparably. No clue how the dose should be modified, if at all.
edit: I've been trying to find out why cimetidine is prescription-only in Australia and the UK but ranitidine isn't. I wonder if it's the interactions from cimetidine. I don't have the time to look further into it any more, but if anyone knows, it'd be nice if they could post.