After a debilitating head injury 30 years ago, and as a result of serious depression from that event; 20mg Fluoxetine (originally Prozac) in the morning, and 25mg doxepin at night, which was essentially to promote sleep, were prescribed. Both meds have consistently been used & worked well. Since doxepin was recently removed from the market, nortriptyline replaced doxepin. After 3+ months on nortriptyline, this med has continuously caused serious sleep deprivation at night. The effects of poor sleep have been significant, including loss of balance. Checking at the pharmacy which supplied these meds, the pharmacist asked: for what main reason was doxepin prescribed? Was it for depression or to promote good night-time sleep, as the Fluoxetine should work successfully for 24 hours for depression. This is the reason for inquiring, and to confirm; how long should the effects of a 20mg Fluoxetine daily med last. Also, is there a better alternative for replacing doxepin without the side effect of disrupted night-time sleep?