indication

For the treatment of depression.

pharmacology

Protriptyline is a tricyclic antidepressant. It was thought that tricyclic antidepressants work by inhibiting the reuptake of the neurotransmitters norepinephrine and serotonin by nerve cells. However, this response occurs immediately, yet mood does not lift for approximately two weeks. It is now thought that changes occur in receptor sensitivity in the cerebral cortex and hippocampus. The hippocampus is part of the limbic system, a part of the brain involved in emotions. Presynaptic receptors are affected: α₁ and β₁ receptors are sensitized, α₂ receptors are desensitised (leading to increased noradrenaline production). Tricyclics are also known as effective analgesics for different types of pain, especially neuropathic or neuralgic pain. A precise mechanism for their analgesic action is unknown, but it is thought that they modulate anti-pain opioid systems in the CNS via an indirect serotonergic route. They are also effective in migraine prophylaxis, but not in abortion of acute migraine attack. The mechanism of their anti-migraine action is also thought to be serotonergic.

mechanism of action

Protriptyline acts by decreasing the reuptake of norepinephrine and serotonin (5-HT).

toxicity

Side effects include anxiety, blood disorders, confusion, decreased libido, dizziness, flushing, headache, impotence, insomnia, low blood pressure, nightmares, rapid or irregular heartbeat, rash, seizures, sensitivity to sunlight, stomach and intestinal discomfort, sedation, hypotension, blurred vision, dry mouth, constipation, urinary retention, postural hypotension, tachycardia, hypertension, ECG changes, heart failure, impaired memory and delirium, and precipitation of hypomanic or manic episodes in bipolar depression. Withdrawal symptoms include gastrointestinal disturbances, anxiety, and insomnia.

route of elimination

Cumulative urinary excretion during 16 days accounted for approximately 50% of the drug. The fecal route of excretion did not seem to be important.

drug interactions

Artemether: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Atazanavir: Atazanavir may increase the effect and toxicity of the tricyclic antidepressant, protriptyline, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of protriptyline if atazanavir if initiated, discontinued or dose changed.

Butabarbital: Barbiturates like butabarbital may increase the metabolism of tricyclic antidepressants like protriptyline. Monitor for decreased therapeutic effects of tricyclic antidepressants if a barbiturate is initiated/dose increased, or increased effects if a barbiturate is discontinued/dose decreased. The tricyclic antidepressant dosage will likely need to be increased during concomitant barbiturate therapy, and reduced upon barbiturate discontinuation.

Butalbital: Barbiturates such as butalbital may increase the metabolism of tricyclic antidepressants such as protriptyline. Monitor for decreased therapeutic effects of tricyclic antidepressants if a barbiturate is initiated/dose increased, or increased effects if a barbiturate is discontinued/dose decreased. The tricyclic antidepressant dosage will likely need to be increased during concomitant barbiturate therapy, and reduced upon barbiturate discontinuation.

Cimetidine: Cimetidine may increase the effect of tricyclic antidepressant, protriptyline, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of trimipramine if cimetidine is initiated, discontinued or dose changed.

Cisapride: Increased risk of cardiotoxicity and arrhythmias

Clonidine: The tricyclic antidepressant, protriptyline, decreases the effect of clonidine.

Desvenlafaxine: Increased risk of serotonin syndrome. Monitor for symptoms of serotonin syndrome.

Donepezil: Possible antagonism of action

Epinephrine: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of epinephrine.

Fenoterol: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of fenoterol.

Fluoxetine: The SSRI, fluoxetine, may increase the serum concentration of the tricyclic antidepressant, protriptyline, by decreasing its metabolism. Additive modulation of serotonin activity also increases the risk of serotonin syndrome. Monitor for development of serotonin syndrome during concomitant therapy. Monitor for changes in the therapeutic and adverse effects of protriptyline if fluoxetine is initiated, discontinued or dose changed.

Fluvoxamine: The SSRI, fluvoxamine, may increase the serum concentration of the tricyclic antidepressant, protriptyline, by decreasing its metabolism. Additive modulation of serotonin activity also increases the risk of serotonin syndrome. Monitor for development of serotonin syndrome during concomitant therapy. Monitor for changes in the therapeutic and adverse effects of protriptyline if fluvoxamine is initiated, discontinued or dose changed.

Galantamine: Possible antagonism of action

Grepafloxacin: Increased risk of cardiotoxicity and arrhythmias

Guanethidine: The tricyclic antidepressant, protriptyline, decreases the effect of guanethidine.

Isocarboxazid: Possibility of severe adverse effects

Lumefantrine: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Moclobemide: Possible severe adverse reaction with this combination

Orciprenaline: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of orciprenaline.

Phenelzine: Possibility of severe adverse effects

Phenylephrine: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of phenylephrine.

Phenylpropanolamine: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of phenylpropanolamine.

Pseudoephedrine: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of pseudoephedrine.

Quinidine: Additive QTc-prolonging effects may occur. Quinidine may also increase the serum concentration of the tricyclic antidepressant, protriptyline, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of protriptyline if quinidine is initiated, discontinued or dose changed. Monitor for the development of torsades de pointes during concomitant therapy.

Rasagiline: Possibility of severe adverse effects

Rifabutin: The rifamycin, rifabutin, may decrease the effect of the tricyclic antidepressant, protriptyline, by increasing its metabolism. Monitor for changes in the therapeutic and adverse effects of protriptyline if rifabutin is initiated, discontinued or dose changed.

Rifampin: The rifamycin, rifampin, may decrease the effect of the tricyclic antidepressant, protriptyline, by increasing its metabolism. Monitor for changes in the therapeutic and adverse effects of protriptyline if rifampin is initiated, discontinued or dose changed.

Tacrine: The therapeutic effects of the central acetylcholinesterase inhibitor, Tacrine, and/or the anticholinergic, Protriptyline, may be reduced due to antagonism. The interaction may be beneficial when the anticholinergic action is a side effect. Monitor for decreased efficacy of both agents.

Tacrolimus: Additive QTc-prolongation may occur increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution.

Terbinafine: Terbinafine may reduce the metabolism and clearance of Protriptyline. Consider alternate therapy or monitor for therapeutic/adverse effects of Protriptyline if Terbinafine is initiated, discontinued or dose changed.

Terbutaline: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of terbutaline.

Terfenadine: Increased risk of cardiotoxicity and arrhythmias

Thiothixene: May cause additive QTc-prolonging effects. Increased risk of ventricular arrhythmias. Consider alternate therapy. Thorough risk:benefit assessment is required prior to co-administration.

Toremifene: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Consider alternate therapy. A thorough risk:benefit assessment is required prior to co-administration.

Tramadol: Tramadol increases the risk of serotonin syndrome and seizures.

Tranylcypromine: Increased risk of serotonin syndrome. Concomitant therapy should be avoided. A significant washout period, dependent on the half-lives of the agents, should be employed between therapies.

Trazodone: Increased risk of serotonin syndrome. Monitor for symptoms of serotonin syndrome.

Trimethobenzamide: Trimethobenzamide and Protriptyline, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Monitor for enhanced anticholinergic effects.

Trimipramine: Increased risk of serotonin syndrome. Monitor for symptoms of serotonin syndrome. Additive QTc-prolongation may also occur, increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution.

Triprolidine: Triprolidine and Protriptyline, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Additive CNS depressant effects may also occur. Monitor for enhanced anticholinergic and CNS depressant effects.

Trospium: Trospium and Protriptyline, two anticholinergics, may cause additive anticholinergic effects and enhanced adverse/toxic effects. Monitor for enhanced anticholinergic effects.

Venlafaxine: Increased risk of serotonin syndrome. Monitor for symptoms of serotonin syndrome.

Voriconazole: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Vorinostat: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Ziprasidone: Additive QTc-prolonging effects may increase the risk of severe arrhythmias. Concomitant therapy is contraindicated.

Zolmitriptan: Use of two serotonin modulators, such as zolmitriptan and protriptyline, increases the risk of serotonin syndrome. Consider alternate therapy or monitor for serotonin syndrome during concomitant therapy.

Zuclopenthixol: Additive QTc prolongation may occur. Consider alternate therapy or use caution and monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).