Circadin is interesting. It is a modified melatonin that is designed to release over an 8 hour period. It is approved for use up to 13 weeks.

It tries to modify the melatonin receptors. I'm not convinced that is the best way to improve sleep. I like to find ways that work with natural cellular processes.

Have you tried taking a 5-HTP supplement? It is not prescription and provides serotonin that can convert to melatonin. As serotonin levels increase from the 5-HTP, when darkness sets in, the body can naturally convert serotonin to melatonin. People who are melatonin deficient may be serotonin deficient. Here is an interesting article about this. Relaxation, a strong bio clock, and better sleep: 5-HTP may help - The Sleep Doctor

Some find 50 mgs in the evening helps. Others need 100 to 150 mgs.