Alzheimers toileting problems usually begin towards the end of the middle stage. The "accidents" will begin. Always stay calm when this happens and remember they will be embarrassed. Bladder control will go first and the loss of bowel control is usually much later.
It is best to begin a routine early on in the disease. Toileting upon first thing in the morning, every two hours during the day, and at bedtime. They will reach a point when they don't realize they need to go to the bathroom. This is where a schedule will help. You will also need to watch for signs they need to toilet. They may pull at their clothing, start wandering, or become fidgety.
At some point you will need to use incontinent products. There are many brands on the market but there are 3 main types of products. There are male guards, they are similar to sanitary napkins. They fit in the front of mens underwear and will catch urine. There are pull up briefs, they look like underwear and are pretty easy to pull up and down. These are appropriate for someone who is still able to get around the house. The last type are the adult diapers. These should be used for people who are bed/chair ridden. They are the easiest to get on and off of someone who can not stand or help you with the process.
When the loss of bladder begins, you will need to take extra measures to keep the private area clean. The disposable wipes are the easiest to use. You will need to watch out for reddened areas. The skin can become irritated, infections are easier to get, and the skin can breakdown. You may also want to invest in a waterproof mattress cover. It is rare for a person with middle or late stage Alzheimer's Disease to make it through the night without wetting. You may want to cut down on the fluids later in the evening. If you do, make sure they are still getting plenty of fluids during the day hours.
There are all kinds of products on the market to help you manage incontinence products at home. There are cloth and disposable bed pads which fit in the middle of the bed to catch urine which can be used along with the pullups or depends to make clean up easier.