Hi,
Surface analgesics and anesthetics have very little effect in cases of pain caused by nerve compression. Your dad needs physiotherapy, oral medication and most probably surgery. Please consult a good neurologist otherwise the continuous nerve compression may sometimes lead to paralysis of the extremities. Decompression of the spinal nerves is necessary. Hope this helps you. Take care and regards!
There is no magic bananna for sciatica. Some people derive relief from capsaican creams. Ocasionally DSMO cream is recommended, however this can be very dangerous, and is not an approved medical procedure. Your dad needs a TENS device, a supply of pads, an extra battery, and instruction in it's use and settings by a health care professional.