Can you help with a traveler medical emergency in Tarija?

We're visiting Bolivia for a 3 months period but are in a medical emergency situation. My husband is getting severe muscle spasms and back pain, so severe that it keeps him up 24-7. He had a pre-existing back problem due to a car accident, but the pain has never been uncontrollable as it is now.

He took Tizanidine in the US, but has run out of it here in Bolivia.

We've gone to the doctors in Tarija, and they proscribed Diclofenaco, Paracetamol and Relazepan 5mg (Valium) as the strongest pain medicine, but nothing seems to calm the pain.

What can we do? Please help, he's in such pain that he cannot move around, so we need something that can help his situation.

Thank you for your time.