My 85 year old MIL is in hospital and weepy and cannot remember why she is there one moment and two hours later she is dry-eyed and upbeat as she tells me she may be in there for a very long time if the myeloma test she takes next week proves to be in the next stages. She is emotionally "off", cries easily, but not when its appropriate and is forgetting things worse than normal. Could this be side effects of the medication?
Can you tie in her more lucid moments to a time passage after an injection? If you can, you might ask that the dosage be decreased. It may make a difference in her thinking without affecting its pain controlling abilities.