I used to take 12.5mg zolpidem (generic Ambien) manufactured by Lupin, India. The tablet is supposedly "slow release" but is not releasing the drug, unless I chew it and hold it in mouth 10 mins. Otherwise, it was not working at all.
FDA is interested only that the generic contains the main drug, nobody actually tests or controls the delivery vehicle. If you read reviews of psychotropic drugs, many people complaining that generics, mostly from India, do not work as the brand name drug.
That is the back side of getting generics from India - nontested and nonregulated drug delivery excipients, hampering the drug effectiveness.