Dear miss_understood,

Valium, or diazepam, is a long acting benzodiazepine while Xanax, or alprazolam, is short acting. The time of onset for Xanax is quicker than that of valium which could be the reason why you find the induction of sleep to be longer when you take Valium. Although they are both given for sleep purposes (amongst other things) Xanax is more effective in the short run. However, with prolonged use of any benzodiazepine, the effectiveness decreases over time which could compound the reason why the switch from Xanax to Valium after a period of use could result in a perceived decreased effectiveness of Valium. I would suggest speaking to your doctor about this. One solution could be alternating between a benzodiazepine and another class of medication for your sleep issues; but remember that sudden ceasation of benzodiazepines could result in withdrawal symptoms. Of course, addressing the underlying reason why you have sleep issues should be the primary goal of care.

Hope this helps!

Dear @miss_understood ,
I very much agree with Dr. R Tay on the need to figure out why your sleep may be elusive. Was there a change in environment? Had there been a change in your health status? Was there a shift in scheduling? 

Before trial of benzodiazepines, we can try Melatonin or Valerian. 
We can also try sedating anti-histamine like Hydroxyzine or Promethazine. 
There has been a new agent in Singapore called Lemborexant or Dayvigo. 
I'll be glad to assist should you wish to know more. Visit https://otium-mindhealth.com or email hello@otium-mindhealth.com 

O_O