I got this tip from Susan and Deborah in part of another thread and thought I'd post it here as its own topic in case others didn't already know this:

I didn't belong to a warehouse/club store because it's just my husband and I, and we don't use things up fast enough to benefit.  Well, when I saw Susan mention she got 180 Zantac for $40 at Costco, I jumped right to their web page to find out more!  It turns out both Costco and Sam's Club offer a wide selection of seriously discounted H1s and H2s in name brand and generic.  I went with Sam's club because it's more convenient to us and the membership fee was $15 less.  

Neither will sell them online, you have to go to the store itself.  

What I got at Sam's Club:
Zantac 150mg (90 count) for $18.52
Allegra 180mg (90 count) for $34.98
Loratadine (generic for my hubby) 10mg (400 count) for $12.88

We easily saved more than the $40 membership fee on our first trip!  

The one hiccup you might have:  Know up front that Costco only takes AmEx.   Sam's, on the other hand, doesn't take AmEx, and in fact doesn't take Visa Credit, only Visa Debit (I don't t know why they take Visa Debit).  They do take Mastercard and Discover.   Of course, they all take cash, but for a big drug haul I wasn't carrying that much!  

Do you know that you can use the pharmacy at Costco without having a membership? You tell them at the door you are going to the pharmacy, and at least in CA, they are required to let you in. I did that a lot before I had a membership, because Costco often had the lowest prices on drugs.

I'm not sure whether you can buy OTC stuff without a membership, but it might be worth a try.