Hello, I'd like to help you with your question.
It sounds like your father could use an evaluation by a therapist. While medication is great for helping cope with symptoms, it cannot address the reasons why your father is feeling this way. Medications also vary in their effectiveness as well. Each person has their own body chemistry and what works for one may not work for another. Also, once you take medication for a while, your body becomes accustomed to it and you either need an increase in dosage or you need to try a new medication. That is why addressing the underlying issue is important. It can eliminate the problem so medications can either be reduced or are not needed at all.
In order to find a therapist, your father can ask his doctor for a referral. Or he can search on line at http://therapists.psychologytoday.com/rms/.
From the symptoms you described, it sounds like your father is depressed. It could be that the surgery triggered it or another event or issue did. Surgery is very difficult to recover from and given your father's age, he may be even more susceptible. Here are some links that can help:
It may also benefit your father (and your family) to have a good support system. You may want to try contacting your local Area Agency on Aging. They may be able to provide companions, Meals on Wheels and evaluations by nurses to assist your father. Depending on their scope of services, they may also be able to provide ACCESS rides and family caregiver support. You can call your local city/county government offices or the United Way for phone numbers and information.
I hope this has helped you,