There is no exact match for Ambien in over the counter form. However, there are several over the counter sleep aids available. Most sleep aids work as antihistimines which produces sleepiness. One powerful antihistimine is Benadryl, an allergy medication. Common sleep aid ingredients are diphenhydramine, which is found in Nytol and Sominex, among other medications. Another sleep aid ingredient is doxylamine, which is found in Unisom and Nighttime Sleep Aid. A natural substance that may contribute a good night's rest is melatonin.