Try asking your pharmacist, though they might turn out to know nothing about 5-HTP. You can also google them and see if there any contraindications listed between these two. You can also try asking your psychiatrist, who "should" know about tryptophan since it was used for many years as an antidepressant and sleep aid by the pharmaceutical industry and medical community. I did notice in a quick google search that if you've taken an ssri within 5 weeks of starting this drug it says to tell your doctor. While HTP doesn't work like an ssri, it is the substance the body uses to make serotonin, and while amitriptyline is a tricyclic, not an ssri, it indicates it may affect serotonin more than a little. The bigger question, of course, is why you're taking an antidepressant to help you sleep.