Yes, there are some medications that are sometimes used to treat behavioral symptoms associated with Alzheimer's. These include antidepressants and antipsychotics. Because they can have serious side effects, they're considered
a last resort. Their use also needs to be monitored carefully. Longterm use of antipsychotics, for example, is associated with twice the risk of death.
Sometimes there are behavioral approaches that can help with difficult behaviors. There are many different reasons for combativeness. See if you can find a trigger for the tough times. Is she getting enough sleep, for example? Does it happen more often when she's frustrated (by not being able to do something, like drink water without spilling)? Could she be overstimulated or feeling hurried? Try using the ABC Method to help you figure out what's triggering the aggression and how you might resolve it.
Also explain exactly what the problem is to your mother's doctor and see what he or she recommends.
You may also wish to review Understanding Alzheimers Symptoms.