You are correct that you should not cut, split or chew Ambien CR (zolpidem controlled release). Doing so will destroy the controlled-release system of the pill, causing the entire dose to be released at once. This defeats the purpose of using Ambien CR!
Ambien Vs. Ambien CR
In regard to the difference between Ambien and Ambien CR, both contain zolpidem. However, Ambien is an immediate-release formulation (zolpidem is released all at once) while Ambien CR tablets have a controlled release mechanism.
After taking Ambien (zolpidem), it is rapidly absorbed and peak concentrations in the blood are seen within 90 minutes. You will begin to feel the effects of the drug within 15-30 minutes and it generally lasts between 4 to 8 hours.
Ambien CR Release
Ambien CR tablets are two-layers and exhibit what is known as 'biphasic' absorption.
After taking a dose by mouth, one layer of the tablet dissolves quickly, providing an immediate-release dose of zolpidem (just like regular Ambien tablets).
The second layer of Ambien CR tablets dissolves more slowly, providing an extended-release dose of zolpidem, and is intended to maintain blood levels of the drug later into the night.
The overall purpose of Ambien CR is to not only help you fall asleep (from the immediate-release zolpidem dose) but also to stay asleep (from the extended-release) dose.
Cutting Ambien Tablets
As mentioned, you should not cut Ambien CR tablets. Doing so will destroy the controlled-release properties of the drug, and you will lose its intended benefit of helping you not only fall asleep but stay asleep.
Regular Ambien tablets (the non-CR version) can safely be cut or split.
Answer SummaryAmbien (zolpidem) is an immediate-release tablet while Ambien CR has two layers, an immediate-release layer and an extended-release layer. Ambien tablets can be cut while Ambien CR tablets cannot be cut.