First, I agree with an earlier post in that the spray is probably something used occasionally to stop nighttime wetness when, say, a child wants to spend the night with a friend and not have to use a pull-up. In my experience, it may or may not work perfectly. We have used the pills in the past and still had nighttime wetness. It decreases amount of urine output (if I remember correctly).
It depends on how old the "older child" is. All my kids are super, super heavy sleepers. That along with a slower developing bladder makes for pull-up use until at least age 8. It wasn't an issue of occasional wetness, they were soaked every night. We went through the pediatric urologist to make sure there were no issues(which may be a good idea-just to be safe), decreased evening fluids, etc. and basically, had to just wait it out. We did use the nighttime alarm, which worked great for the boys, but my daughter seems to have more anxiety with the alarm, so we are just waiting it out, mostly.
I have heard parents say they make the child help them "clean up" the bedding after an accident. I personally, don't agree with this. If in fact there's nothing medically wrong, and the child is a very heavy sleeper...they cannot help it. It is not something they are doing out of spite or to irritate you. They sleep through the body's cues to wake and go to the bathroom. For my oldest two, the alarms helped trigger the brain to wake and, eventually, they became drier and drier each night.
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So, the spray or the pills that help decrease urine output can help once in a while, but we were told that it is not a cure for bedwetting, just something you can use occasionally.
An alarm can be useful, it really just depends on the kid whether it works or not. For us, we would put my son to bed with the alarm and I slept with a baby monitor. This way I could hear the alarm and get him up. Like I said, my kids will sleep through anything, including the bedwetting alarm! The alarm will detect when the underwear gets wet, so you may have to help him change underwear, etc. We would put underwear on then a pull-up over it, so that we didn't have to deal with wet bedding each and every night. However, the alarm did go off at the first detection of wetness, so he may wake up or you may get to him before he's soaked.
I wish you luck. We have been through these nighttime bedwetting issues and I know it can be very frusterating. Sometimes some kids just need a little more time to develop those bladders. :)