PRONERVE NT

Indications

• Depressive illness
• Neuropathic pain

Dosage

Children: For children aged 12–17 years, treatment should begin at a low dose, increasing if necessary to 30–50 mg daily in divided doses or alternatively taken once daily. The maximum dose is 150 mg per day.

Adults: Initially, 10 mg once daily, preferably at night, which may be increased to 75 mg daily if necessary, with the maximum dose being 150 mg per day.

Mechanism of action

Nortriptyline is thought to inhibit the reuptake of serotonin and norepinephrine at neuronal membranes, with a more selective action on norepinephrine. This action enhances mood and alleviates depressive symptoms. Additionally, it interacts with various other receptors including muscarinic acetylcholine receptors and histamine receptors, which may contribute to both its therapeutic effects and side effects.

Pharmacodynamics

Nortriptyline exhibits antidepressant effects primarily through the inhibition of serotonin and norepinephrine reuptake, leading to increased levels of these neurotransmitters in the synaptic cleft. It also has antimuscarinic properties which can lead to side effects such as dry mouth and urinary retention. The drug's affinity for multiple receptors may influence its overall therapeutic efficacy and side effect profile.

Pharmacokinetics

Nortriptyline is well absorbed following oral administration, with peak plasma concentrations typically occurring within 4 to 8 hours. It undergoes extensive hepatic metabolism, primarily via cytochrome P450 enzymes, and has a half-life of about 18 to 44 hours. The drug is mostly excreted as metabolites in the urine. Dosing adjustments may be necessary in patients with hepatic impairment. Regular monitoring of plasma levels may be warranted in patients receiving higher doses.

Contra-indications

• Arrhythmias during the manic phase of bipolar disorder
• Heart block
• Immediate recovery period after myocardial infarction

Adverse effects

• Dry mouth
• Drowsiness
• Constipation
• Urinary retention
• Hypotension
• Cardiac conduction defects
• Arrhythmias
• Dilated pupils
• Suicidal tendencies
• Neurological effects
• Increased risk of fracture
• Photosensitivity reaction
• Respiratory disorders
• Thrombocytopenia
• Anticholinergic syndrome

Interactions

• Severe: dacomitinib increases exposure
• Moderate: eliglustat increases exposure
• Unknown: valproate increases concentration

Precautions

• Caution in patients with cardiovascular disease
• Caution in patients with chronic constipation
• Caution in patients with diabetes
• Caution in patients with epilepsy
• History of bipolar disorder
• History of alcohol dependence
• History of hyperthyroidism (risk of arrhythmias)
• Elderly patients may be particularly susceptible to side effects

Pregnancy

Use only if potential benefit outweighs risk.

Breast-feeding

The amount secreted into breast milk is too small to be harmful.

Storage

Store in a cool, dry place away from light.

Formulations

• Nortriptyline (as Nortriptyline hydrochloride) 10 mg/5 ml oral solution
• Nortriptyline tablets 10 mg
• Nortriptyline tablets 25 mg
• Nortriptyline capsules 10 mg
• Nortriptyline capsules 25 mg

Indications

• Epilepsy
• Neuropathic pain
• Generalized anxiety disorder

Dosage

Adults: The usual starting dose is 150 mg daily, divided into two or three doses. The dose may be increased to a maximum of 600 mg daily based on clinical response and tolerability. Refer to the BNF for specific dosing adjustments in

Mechanism of action

Pregabalin binds presynaptically to the alpha2-delta subunit of voltage-gated calcium channels in the central nervous system. This binding modulates the release of several excitatory neurotransmitters, including glutamate, substance P, norepinephrine, and calcitonin gene-related peptide. By preventing the trafficking of the alpha2-delta subunit from the dorsal root ganglia to the spinal dorsal horn, pregabalin contributes to its anticonvulsant and analgesic effects.

Pharmacodynamics

Pregabalin increases the density of GABA transporters in cultured neurons but does not bind directly to GABA-A, GABA-B, or benzodiazepine receptors. It does not affect dopamine, serotonin, or opiate receptors, nor does it modulate sodium channels or cyclooxygenase activity. Its primary action is through the inhibition of excitatory neurotransmitter release, which helps in controlling seizures and alleviating neuropathic pain.

Pharmacokinetics

Pregabalin is rapidly absorbed after oral administration, with peak plasma concentrations usually reached within 1 hour. It has a bioavailability of approximately 90%, and its plasma concentration does not significantly change with increasing doses. Pregabalin is not extensively metabolized; it is primarily excreted unchanged in the urine. The elimination half-life is about 6 hours, and dose adjustments may be necessary in patients with renal impairment.

Adverse effects

• Dizziness
• Somnolence
• Dry mouth
• Edema
• Weight gain
• Blurred vision
• Difficulty concentrating
• Euphoria
• Depression
• Angioedema

Interactions

• CNS depressants may enhance the sedative effects of pregabalin
• Concurrent use with opioids may increase the risk of respiratory depression
• Antiepileptic drugs may have additive effects

Precautions

• Use with caution in patients with a history of substance abuse
• Monitor for signs of angioedema, especially in patients with a history of angioedema
• Caution in patients with renal impairment, as dosage adjustments may be necessary

Pregnancy

Pregabalin is classified as category C. Animal studies have shown adverse effects, and there are no well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Pregabalin is excreted in breast milk. The effects on a nursing infant are unknown, and caution is advised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Capsules: 25 mg, 50 mg, 75 mg, 100 mg, 150 mg, 200 mg, 225 mg, 300 mg
• Oral solution: 20 mg/mL
• Chewable tablets: 50 mg

Mechanism of action

Though prescribing information does not identify a specific mechanism of action for nortriptyline, is believed that nortriptyline either inhibits the reuptake of the neurotransmitter serotonin at the neuronal membrane or acts at the level of the beta-adrenergic receptors. It displays a more selective reuptake inhibition for noradrenaline, which may explain increased symptom improvement after nortriptyline therapy. Tricyclic antidepressants do not inhibit monoamine oxidase nor do they affect dopamine reuptake. As with other tricyclics, nortriptyline displays affinity for other receptors including mACh receptors, histamine receptors, 5-HT receptors, in addition to other receptors. The mechanism of adverse imipramine-induced reactions ... was investigated by precipitating such reactions in rats with three injections (ip) of imipramine (5-40 mg/kg) at 24, 5, and 1 hr before testing, and comparing their occurrence with comparable treatments using specific noradrenergic and serotonergic reuptake inhibitors (nortriptyline (10 or 30 mg/kg, ip), citalopram (0.5-5.0 mg/kg, ip)). This initial study indicated that these reactions were mediated by imipramine's noradrenergic effects. The effect of equal-dose regimens of amitriptyline and nortriptyline on the concn of serotonin, dopamine and major acidic metabolites was compared in 5 distinct brain regions as a function of inbred mouse strain. Amitriptyline incr to a greater extent the regional brain serotonin levels in the albino BALB/c mouse than did nortriptyline. Both drugs incr serotonin levels but decr cerebral 5-hydroxyindoleacetic acid levels in some distinct brain regions of the black C57BL/6 mouse strain. The results suggest a strain-dependent differential incr in brain serotonin turnover in specific mouse strain brain regions which may account for the greater incidence of amitriptyline-induced sedation and seizures. The BALB/c mouse was also found to be more sensitive than the C57BL/6 strain to the action of both drugs on dopamine and major acidic metabolites with amitriptyline showing more regional brain potency than nortriptyline. The data suggest an incr in dopamine turnover particularly in brain areas assoc with motor function and posture which may account for tricyclic antidepressant-induced extrapyramidal disorders. The results also indicate that the C57BL/6 mouse strain may be of experimental value for studying the mechanism underlying tricyclic-induced adverse reactions relevant to sedation and movement disorders as a function of genetic predisposition. Neuropathic pain is pain arising as a direct consequence of a lesion or disease affecting the somatosensory system. It is usually chronic and challenging to treat. Some antidepressants are first-line pharmacological treatments for neuropathic pain. The noradrenaline that is recruited by the action of the antidepressants on reuptake transporters has been proposed to act through beta2-adrenoceptors (beta2-ARs) to lead to the observed therapeutic effect. However, the complex downstream mechanism mediating this action remained to be identified. In this study, we demonstrate in a mouse model of neuropathic pain that an antidepressant's effect on neuropathic allodynia involves the peripheral nervous system and the inhibition of cytokine tumor necrosis factor a (TNFa) production. The antiallodynic action of nortriptyline is indeed lost after peripheral sympathectomy, but not after lesion of central descending noradrenergic pathways. More particularly, we report that antidepressant-recruited noradrenaline acts, within dorsal root ganglia, on beta2-ARs expressed by non-neuronal satellite cells. This stimulation of beta2-ARs decreases the neuropathy-induced production of membrane-bound TNFa, resulting in relief of neuropathic allodynia. This indirect anti-TNFa action was observed with the tricyclic antidepressant nortriptyline, the selective serotonin and noradrenaline reuptake inhibitor venlafaxine and the beta2-AR agonist terbutali

Pharmacodynamics

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.

Mechanism of action

Although the mechanism of action has not been fully elucidated, studies involving structurally related drugs suggest that presynaptic binding of pregabalin to voltage-gated calcium channels is key to the antiseizure and antinociceptive effects observed in animal models. By binding presynaptically to the alpha2-delta subunit of voltage-gated calcium channels in the central nervous system, pregabalin modulates the release of several excitatory neurotransmitters including glutamate, substance-P, norepinephrine, and calcitonin gene related peptide. In addition, pregabalin prevents the alpha2-delta subunit from being trafficked from the dorsal root ganglia to the spinal dorsal horn, which may also contribute to the mechanism of action. Although pregabalin is a structural derivative of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), it does not bind directly to GABA or benzodiazepine receptors. Pregabalin is an anticonvulsant that is structurally related to the inhibitory CNS neurotransmitter gamma-aminobutyric acid (GABA). Pregabalin also has demonstrated analgesic activity. Although pregabalin was developed as a structural analog of GABA, the drug does not bind directly to GABA-A, GABA-B, or benzodiazepine receptors; does not augment GABA-A responses in cultured neurons; and does not alter brain concentrations of GABA in rats or affect GABA uptake or degradation. However, in cultured neurons, prolonged application of pregabalin increases the density of GABA transporter protein and increases the rate of functional GABA transport. Pregabalin binds with high affinity to the alpha2-delta site (an auxiliary subunit of voltage-gated calcium channels) in CNS tissues. ... In vitro, pregabalin reduces the calcium-dependent release of several neurotransmitters, including glutamate, norepinephrine, and substance P, possibly by modulation of calcium channel function. Pregabalin does not block sodium channels, is not active at opiate receptors, and does not alter cyclooxygenase enzyme activity. It is inactive at serotonin and dopamine receptors and does not inhibit dopamine, serotonin, or noradrenaline reuptake. Pregabalin is a potent ligand for the alpha-2-delta subunit of voltage-gated calcium channels in the central nervous system that exhibits potent anticonvulsant, analgesic, and anxiolytic activity in a range of animal models. ... Potent binding to the alpha-2-delta site reduces depolarization-induced calcium influx with a consequential modulation in excitatory neurotransmitter release. Pregabalin has no demonstrated effects on GABAergic mechanisms. ... For more Mechanism of Action (Complete) data for PREGABALIN (6 total), please visit the HSDB record page.

Pharmacodynamics

Although the structure of pregabalin is similar to gamma-aminobutyric acid (GABA), it does not bind to GABA receptors. Instead, it binds the alpha2-delta subunit of presynaptic voltage-gated calcium channels in the central nervous system. Pregabalin does not modulate dopamine receptors, serotonin receptors, opiate receptors, sodium channels or cyclooxygenase activity.