Hbp: can a 20mg uncoated/unscored lisinopril extended release tab be evenly divided for am & pm to decrease side effects?

No: It is best not to cut it. It is possible that the drug is not evenly distributed. There are 10 mg tab available. Review this with the doctor.

Side effects : What side effects (s) are your talking about that Lisinopril (l) is causing? If it a cough (c). You should discuss your s with your physician (p). If it's a c, stop the l for two days. If the cough goes away, tell you p to put you on a different BP medication. If the c remains, it is not due to l and could be due to esophageal reflux, among others. Discuss your problem with you p for more advice.