Within 24 hours of a dose of amitriptyline, the body typically excretes one-third to one-half of the drug, according to Drugs.com. The amount of time it takes for the drug to completely exit the body varies significantly, based upon the individual patient and the dose of the medication.
Amitriptyline is a tricyclic antidepressant that works by helping the brain maintain mental balance, states MedlinePlus. It is used to control depression, prevent migraine headaches and treat eating disorders. Amitriptyline is usually taken one to four times a day, and several weeks of treatment may be required to feel the full effect of this medication.