NORTRIPTYLINE

Absorption

Nortriptyline is readily absorbed in the gastrointestinal tract with extensive variation in plasma levels, depending on the patient. This drug undergoes first-pass metabolism and its plasma concentrations are attained within 7 to 8.5 hours after oral administration. The bioavailability of nortriptyline varies considerably and ranges from 45 to 85%.

Toxicity

The oral LD50 of nortriptyline in the rat is 405 mg/kg.Symptoms of overdose with nortriptyline include cardiac arrhythmias, severe hypotension, shock, congestive heart failure, pulmonary edema, convulsions, coma, and CNS depression. Changes in the electrocardiogram, particularly in QRS segment, may be indicative of tricyclic antidepressant toxicity.

Originator

Aventyl,Lilly,UK,1963

The Uses of NORTRIPTYLINE

Nortriptyline is a drug with a relatively short latent period of action. It is practically devoid of sedative effects. It is used in manic-depressive psychoses, in all forms of endogenous depression, and also in major depressive conditions.

The Uses of NORTRIPTYLINE

Antidepressant.

Background

Nortriptyline hydrochloride, the active metabolite of amitriptyline, is a tricyclic antidepressant (TCA). It is used in the treatment of major depression and is also used off-label for chronic pain and other conditions.

Indications

Nortriptyline is indicated for the relief of the symptoms of major depressive disorder (MDD). Some off-label uses for this drug include treatment of chronic pain, myofascial pain, neuralgia, and irritable bowel syndrome.

Definition

ChEBI: An organic tricyclic compound that is 10,11-dihydro-5H-dibenzo[a,d][7]annulene substituted by a 3-(methylamino)propylidene group at position 5. It is an active metabolite of amitriptyline.

Manufacturing Process

A mixture of 114.5 g of 5-(3-chloropropylidene)dibenzo[a,d]cyclohepta[1,4] diene, 75 ml of benzene, and about 400 ml of methylamine is heated in an autoclave at 120°C for six hours. The excess methylamine is distilled from the reaction mixture under vacuum and the residue is stirred with 300 ml of water. Acidification of the mixture with hydrochloric acid causes the separation of the hydrochloride of 5-(3-methylaminopropylidene)dibenzo[a,d] cyclohepta[1,4]diene. The product is collected by filtration and is purified by recrystallization from a mixture of absolute ethanol and ethyl acetate. MP 210°C to 212°C.

brand name

Aventyl Hydrochloride (Lilly); Aventyl Hydrochloride (Ranbaxy); Pamelor (Tyco).

Therapeutic Function

Antidepressant

Pharmacokinetics

Nortriptyline exerts antidepressant effects likely by inhibiting the reuptake of serotonin and norepinephrine at neuronal cell membranes. It also exerts antimuscarinic effects through its actions on the acetylcholine receptor.

Clinical Use

Tricyclic antidepressant

Safety Profile

Poison by ingestion,intraperitoneal, and intravenous routes. When heated todecomposition it emits toxic fumes of NOx.

Synthesis

Nortriptyline is 5-(3-methylaminopropyliden)-10,11-dihydrodibenzcycloheptene (7.1.17). Nortriptyline differs from desipramine in the same manner in which amitriptyline differs from imipramine. In nortriptyline, the nitrogen atom in the central part of the tricyclic system of desipramine is replaced by a carbon atom, which is bound to a side chain by a double bond.
Two suggested methods of nortriptyline synthesis are based on the N-demethylation of amitriptyline. The third way utilizes the reaction of methylamine with 5-(3-bromopropyliden)-10,11-dihydro-5H-dibenz[a,d]cycloheptene (7.1.18).
According to the first scheme, demethylation takes place by the reaction of amitriptyline (7.1.4) with methyliodide, which leads to the formation of a quaternary ammonium salt (7.1.16), the reaction of which with methylamine at a relatively high temperature gives the desired nortriptyline (7.1.17) [25].

According to the third scheme, nortriptyline is synthesized by reacting methylamine with 5-(3-bromopropyliden)-10,11-dihydro-5H-dibenz[a,d]cycloheptene (7.1.6) [8].

Drug interactions

Potentially hazardous interactions with other drugs
Alcohol: increased sedative effect.
Analgesics: increased risk of CNS toxicity with tramadol; possibly increased risk of side effects with nefopam; possibly increased sedative effects with opioids.
Anti-arrhythmics: increased risk of ventricular arrhythmias with amiodarone - avoid; increased risk of ventricular arrhythmias with disopyramide, flecainide or propafenone; avoid with dronedarone.
Antibacterials: increased risk of ventricular arrhythmias with delamanid, moxifloxacin and possibly telithromycin - avoid with moxifloxacin.
Anticoagulants: may alter anticoagulant effect of coumarins.
Antidepressants: enhanced CNS excitation and hypertension with MAOIs and moclobemide - avoid; concentration possibly increased with SSRIs; risk of ventricular arrhythmias with citalopram and escitalopram - avoid; increased risk of convulsions with vortioxetine.
Antiepileptics: convulsive threshold lowered; concentration reduced by carbamazepine, fosphenytoin, phenobarbital and possibly phenytoin.
Antimalarials: avoid with artemether/lumefantrine and piperaquine with artenimol.
Antipsychotics: increased risk of ventricular arrhythmias especially with droperidol, haloperidol, pimozide, risperidone and sulpiride - avoid; increased antimuscarinic effects with clozapine and phenothiazines; concentration increased by antipsychotics.
Antivirals: increased risk of ventricular arrhythmias with saquinavir - avoid; concentration possibly increased with ritonavir.
Atomoxetine: increased risk of ventricular arrhythmias and possibly convulsions.
Beta-blockers: increased risk of ventricular arrhythmias with sotalol.
Clonidine: tricyclics antagonise hypotensive effect; increased risk of hypertension on clonidine withdrawal.
Dapoxetine: possible increased risk of serotonergic effects - avoid.
Dopaminergics: avoid use with entacapone; CNS toxicity reported with selegiline and rasagiline.
Pentamidine: increased risk of ventricular arrhythmias.
Sympathomimetics: increased risk of hypertension and arrhythmias with adrenaline and noradrenaline; metabolism possibly inhibited by methylphenidate.

Metabolism

Nortriptyline is metabolized via demethylation and hydroxylation in the liver followed by glucuronic acid conjugation. CYP2D6 plays a large role in nortriptyline metabolism, with contributions from CYP1A2, CYP2C19 and CYP3A4. The main active metabolite is 10-hydroxynortriptyline exists in both cis and a trans form, with the trans form is higher in potency. 10-hydroxynortriptyline is the most frequently found in the plasma. Most of the other metabolites are conjugated, and are less potent.

Metabolism

Nortriptyline is a secondary amine dibenzocycloheptene TCA as well as the major metabolite of amitriptyline. Similar to desipramine, nortriptyline appears in mother's milk and is metabolized by CYP2D6 to the primary amine and by ring hydroxylation to its E-10-hydroxy metabolite. Approximately one-third of a dose of nortriptyline is excreted in urine as metabolites within 24 hours, and small amounts are excreted in feces via biliary elimination.