Does anyone know if the cost of adult diapers is deductible for a person with prostate cancer who no longer has an urge to urinate?

If your husband is a Veteran the VA will provide incontinence supplies. And depending on where an when he served he may qualify for a lot more.
Incontinence supplies are a Medical Expense and if you meet deductions they can be declared.
If he qualifies for Hospice, Hospice will also provide all the incontinence supplies you need. This includes wipes, creams, gloves and under pads.

When you do your IRS work with your CPA or other tax person you will inform of medical expenses. I do believe in total they have to raise to a certain amount to be deductible. You don't need to go into EACH one in detail, just have with your records in case ever questioned regarding your tax deductions in an audit.

You should definitely check with your medical coverage for your supplemental costs, as often these supplies are covered for medical conditions.

Good luck.

Does he generally itemize on his tax return?

All of his medical deductions would need to total 7.5% of his taxable income. (Check that figure; it has changed in the last 2 years).

https://www.kxan.com/business/press-releases/ein-presswire/644061353/irs-updates-medical-expenses-tax-deduction-for-2023/#:~:text=The%20new%20deduction%20allows%20taxpayers,adjusted%20gross%20income%20(AGI).&text=To%20claim%20the%20medical%20expenses,expenses%2C%20including%20receipts%20and%20invoices.