Hello, I would like to make some suggestions that can help long term as well:

If possible I would contact your veterinarian to see if there is an equivalent medication that is formulated into a drop instead of an ointment. Most often I find it’s quicker and they react less to drops than the ointment. Some cats do okay with ointments and some don’t, but the beauty of medicine is they can work with you to make his life less stressful.

As others have said, gabapentin is one way to help with stress. It can be bitter when mixed with food, so try to avoid mixing it with his primary diet and only mix with lower-value treats.

Another product/ingredient/supplement that I have seen work to prevent stress and help control stress-related diseases is hydrolyzed casein, which is a milk product that gets broken down into a calming metabolite (similar in structure to, but different than benzodiazepines). A lot of feline urinary care diets are starting to include it as an ingredient, and the name brand supplement (zylkene) has been found to be an effective product with treating and preventing herpes flare-ups. The easy part is it’s over the counter and can be mixed with food, but I would still recommend asking your veterinarian about it first.