A level between 50 and 150 ng/mL of nortriptyline in the blood generally corresponds with an antidepressant effect.In the United Kingdom, it may also be used for treating nocturnal enuresis, with courses of treatment lasting no more than three months. It is also used off-label for the treatment of panic disorder, irritable bowel syndrome, migraine prophylaxis and chronic pain or neuralgia modification, particularly temporomandibular joint disorder. Neuropathic pain
Although not approved by the FDA for neuropathic pain, many randomized controlled trials have demonstrated the effectiveness of TCAs for the treatment of this condition in both depressed and non-depressed individuals. In 2010, an evidence-based guideline sponsored by the International Association for the Study of Pain recommended nortriptyline as a first-line medication for neuropathic pain. However, in a 2015 Cochrane systematic review the authors did not recommend nortriptyline as a first-line agent for neuropathic pain. Irritable Bowel Syndrome
Nortriptyline has also been used as an off-label treatment for Irritable Bowel Syndrome, or IBS. Contraindications
Nortriptyline should not be used in the acute recovery phase after myocardial infarction (viz, heart attack). Use of tricyclic antidepressants along with a monoamine oxidase (MAO) inhibitor, linezolid, and IV methylene blue are contraindicated as it can cause an increased risk of developing serotonin syndrome.Closer monitoring is required for those with a history of cardiovascular disease, stroke,  glaucoma, or seizures, as well as in persons with hyperthyroidism or receiving thyroid hormones. Side effects
The most common side effects include dry mouth, sedation, constipation, increased appetite, blurred vision and tinnitus.
An occasional side effect is a rapid or irregular heartbeat. Alcohol may exacerbate some of its side effects. Overdose
The symptoms and the treatment of an overdose are generally the same as for the other TCAs, including anticholinergic effects,  serotonin syndrome and adverse cardiac effects. TCAs, particularly nortriptyline, have a relatively narrow therapeutic index, which increase the chance of an overdose (both accidental and intentional). Symptoms of overdose include: irregular heartbeat, seizures, coma, confusion, hallucination, widened pupils, drowsiness, agitation, fever, low body temperature, stiff muscles and vomiting. Interactions
Excessive consumption of alcohol in combination with nortriptyline therapy may have a potentiating effect, which may lead to the danger of increased suicidal attempts or overdosage, especially in patients with histories of emotional disturbances or suicidal ideation. It may interact with the following drugs:
heart rhythm medications such as flecainide (Tambocor), propafenone (Rhythmol), or quinidine (Cardioquin, Quinidex, Quinaglute)
cimetidine
guanethidine
reserpine

Pharmacology
Nortriptyline is a strong norepinephrine reuptake inhibitor and a moderate  serotonin reuptake inhibitor. Its pharmacologic profile is as the table shows with (inhibition or antagonism of all sites). Pharmacodynamics
Nortriptyline is an active metabolite of amitriptyline by demethylation in the liver. Chemically, it is a secondary amine dibenzocycloheptene and pharmacologically it is classed as a first-generation antidepressant.Nortriptyline may also have a sleep-improving effect due to antagonism of the H1 and 5-HT2A receptors. In the short term, however, nortriptyline may disturb sleep due to its activating effect.