Pharmacology question - which drugs tend to have generics that may not be equal to the brand name drugs?

Depends: Drug effect depends not only on the active ingredient but on bioavailability, absorption, distribution, excretion. Generics are not required to match branded drug's bioavailability, etc. Or purity of non active components. Med that depends on these characteristics could be less effective in genetic form. One could ingest generic but not absorb or distribute it efficiently = less/different effect.

Some not all: Those drugs that have a very small difference between effectiveness and toxicity (narrow therapeutic window) are often the target of generic versus brand. Some drugs that fall into this category include warfarin, digoxin, and Phenytoin (extended release capsules). This "window" pertains to oral drugs not usually to injectables.