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.
Nortriptyline, sold under the brand name Pamelor, among others, is a medication used to treat depression. This medicine is used for: neuropathic pain, attention deficit hyperactivity disorder (ADHD), smoking cessation and anxiety. As with many antidepressants, its use for young people with depression and other psychiatric disorders may be limited due to increased suicidality in the 18-24 population initiating treatment. Nortriptyline is a less preferred treatment for ADHD and stopping smoking. It is taken by mouth.Common side effects include dry mouth, constipation, blurry vision, sleepiness, low blood pressure with standing, and weakness. Serious side effects may include seizures, an increased risk of suicide in those less than 25 years of age, urinary retention, glaucoma, mania, and a number of heart issues. Nortriptyline may cause problems if taken during pregnancy. Use during breastfeeding appears to be relatively safe. It is a tricyclic antidepressant (TCA) and is believed to work by altering levels of serotonin and norepinephrine.Nortriptyline was approved for medical use in the United States in 1964. It is available as a generic medication. In 2019, it was the 153rd most commonly prescribed medication in the United States, with more than 4 million prescriptions. Medical uses
Nortriptyline is used to treat depression. This medication is in capsule or liquid and is taken by the mouth one to four times a day, with or without food. Usually people are started on a low dose and it is gradually increased.