|Systematic (IUPAC) name|
|Biological half-life||16 and 90 hours|
|CAS Registry Number||
|Molecular mass||263.38 g/mol|
|(what is this?)|
Nortriptyline is a second-generation tricyclic antidepressant (TCA) marketed as the hydrochloride salt under the trade names Sensoval, Aventyl, Pamelor, Norpress, Allegron, Noritren and Nortrilen. It is used in the treatment of major depression and childhood nocturnal enuresis (bedwetting). In addition, it is sometimes used for chronic illnesses such as chronic fatigue syndrome, chronic pain and migraine, and labile affect in some neurological conditions.
Nortriptyline is FDA-approved for the treatment of major depression. 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. It can also aid in quitting smoking, with one study showing a six-month abstinence rate of 14% for subjects receiving nortriptyline compared to 3% for subjects not undergoing pharmacological treatment. A controlled study suggests it reduces symptoms of ADHD.
Although not approved by the FDA for neuropathic pain, a large number of randomized controlled trials have proven the efficacy of tricyclic antidepressants for the treatment of this condition in both depressed and non-depressed individuals. Recently, an evidence-based guideline sponsored by the International Association for the Study of Pain recommends nortriptyline as a first-line medication for neuropathic pain.
The most common side effects include dry mouth, sedation, constipation, and increased appetite, mild blurred vision, tinnitus, often euphoria and mania. An occasional side effect is a rapid or irregular heartbeat. Alcohol may exacerbate some of its side effects and should be avoided.
However, the incidence of side effects with nortriptyline is lower than with the first-generation tricyclics (e.g., imipramine (Tofranil), amitriptyline (Elavil)). For this reason it is often used in elder patients instead of other TCAs to reduce side effects and improving patient's compliance.
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.
Nortriptyline should not be used in the acute recovery phase after myocardial infarction (e.g., heart attack). As for all tricyclic antidepressants, concurrent use, or failure to allow a two-week gap with monoamine oxidase inhibitors (MAO inhibitors, e.g., phenelzine, tranylcypromine, etc.) may precipitate hyperpyretic crisis caused by serotonin syndrome or severe convulsions.
The symptoms and the treatment of an overdose are largely the same as for the other tricyclic antidepressants, including serotonin syndrome and adverse cardiac effects. As tricyclic antidepressants have a relatively narrow therapeutic index, the likelihood of overdose (both accidental and intentional) is fairly high and should be considered carefully by the prescribing physician prior to patient use.
A nortriptyline overdose should always be considered a medical emergency and can result in death. In the event of a known or suspected overdose, poison control (1-800-222-1222 in the U.S.) or 911 (999 in the U.K.) should be contacted immediately. If no phone services are available the overdose victim should be brought to the nearest hospital as soon as possible.
Nortriptyline is metabolized in the liver by the hepatic enzyme CYP2D6, and genetic variations within the gene coding for this enzyme can affect its metabolism, leading to changes in the concentrations of the drug in the body. Increased concentrations of nortriptyline may increase the risk for side effects, including anticholinergic and nervous system adverse effects, while decreased concentrations may reduce the drug's efficacy.
Individuals can be categorized into different types of CYP2D6 metabolizers depending on which genetic variations they carry. These metabolizer types include poor, intermediate, extensive, and ultrarapid metabolizers. Most individuals (about 77-92%) are extensive metabolizers, and have "normal" metabolism of nortriptyline. Poor and intermediate metabolizers have reduced metabolism of the drug as compared to extensive metabolizers; patients with these metabolizer types may have an increased probability of experiencing side effects. Ultrarapid metabolizers use nortriptyline much faster than extensive metabolizers; patients with this metabolizer type may have a greater chance of experiencing pharmacological failure.
The Clinical Pharmacogenetics Implementation Consortium recommends avoiding nortriptyline in patients who are CYP2D6 ultrarapid or poor metabolizers, due to the risk for a lack of efficacy and side effects, respectively. A reduction in starting dose is recommended for patients who are CYP2D6 intermediate metabolizers. If use of nortriptyline is warranted, therapeutic drug monitoring is recommended to guide dose adjustments. The Dutch Pharmacogenetics Working Group recommends reducing the dose of nortriptyline in CYP2D6 poor or intermediate metabolizers, and selecting an alternative drug or increasing the dose in ultrarapid metabolizers.
|Receptor/Transporter Protein||Binding Affinity (Ki[nM])||Receptor location and species|
|Sigma receptor||2000||Guinea pig, brain|
These effects account for some therapeutic actions as well as for most side effects such as sedation, hypotension, anticholinergic effects, etc. Nortriptyline may also have a sleep-improving effect due to its affinity for 5HT2A and histaminergic receptors. In the short term; however, nortriptyline may disturb sleep due to its activating effect.
In one study of long-term efficacy, nortriptyline showed a higher relapse rate in comparison with phenelzine in individuals being treated for depression, possibly due to the metabolite 10-hydroxynortriptyline being produced. The authors of a review noted that the nortriptyline group had more episodes prior to treatment.
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