Took 0.5mg klonopin (clonazepam) the other night & slept well. terrible sleep since then (3 consecutive nights now). can 1 tab of klonopin (clonazepam) change your chemistry?

Not likely: the insomnia is probably not related to the single dose of Klonopin (clonazepam). See your doctor to determine the cause of the sleep disturbance

Sleep meds: Benzodiazepines are CNS depressants so they will help you to relax but daily use over a long time can produce tolerance. But that is not a permanent brain chemistry change. If you already had bad sleep problems please see a Psychologist expert in sleep disorders for good eval and effective treatment. You can have good sleep and not have to take sleep meds long term!