Bummer you have these side effects. Both of those cold be related, obviously. The dry cracking lips is common. If it is really bad or worsens, that is something to tell either your doctor or your pharmacist about. The back pain is something that they say to promptly report to your doctor as that could be a rarer more serious side effect (they say joint and back/muscle pain). So, you need to check in with your doctor after reading this about it. Let me know what they say!