Hello,
You have not mentioned any thing about his regular health check up, since these two drugs can have adverse effect on both
liver and kidney, you need to monitor the health of these organs on a regular basis.
Liver health is closely associated with libido. So, I would suggest you to consult your doctor and go for an over all health check up. If everything is found Ok, may be you need to check for his hormone levels also. I am sure, you should be able to get a solution.