indication

For treatment of depression, including the depressed phase of bipolar depression, psychotic depression, and involutional melancholia, and may also be helpful in treating certain patients suffering severe depressive neurosis.

pharmacology

Maprotiline is a tetracyclic antidepressant. Although its main therapeutic use is in the treatment of depression, it has also been shown to exert a sedative effect on the anxiety component that often accompanies depression. In one sleep study, it was shown that maprotiline increases the duration of the REM sleep phase in depressed patients, compared to imipramine which reduced the REM sleep phase. Maprotiline is a strong inhibitor of noradrenaline reuptake in the brain and peripheral tissues, however it is worthy to note that it is a weak inhibitor of serotonergic uptake. In addition, it displays strong antihistaminic action (which may explain its sedative effects) as well as weak anticholinergic action. Maprotiline also has lower alpha adrenergic blocking activity than amitriptyline.

mechanism of action

Maprotiline exerts its antidepressant action by inhibition of presynaptic uptake of catecholamines, thereby increasing their concentration at the synaptic clefts of the brain. In single doses, the effect of maprotiline on the EEG revealed a rise in the alpha-wave density, a reduction of the alpha-wave frequency and an increase in the alpha-wave amplitude. However, as with other tricyclic antidepressants, maprotiline lowers the convulsive threshold. Maprotiline acts as an antagonist at central presynaptic α₂-adrenergic inhibitory autoreceptors and hetero-receptors, an action that is postulated to result in an increase in central noradrenergic and serotonergic activity. Maprotiline is also a moderate peripheral α₁ adrenergic antagonist, which may explain the occasional orthostatic hypotension reported in association with its use. Maprotiline also inhibits the amine transporter, delaying the reuptake of noradrenaline and norepinephrine. Lastly, maprotiline is a strong inhibitor of the histamine H₁ receptor, which explains its sedative actions.

toxicity

LD₅₀=~900 mg/kg (Orally in rats); LD₅₀=90 mg/kg (Orally in women); Signs of overdose include motor unrest, muscular twitching and rigidity, tremor, ataxia, convulsions, hyperpyrexia, vertigo, mydriasis, vomiting, cyanosis, hypotension, shock, tachycardia, cardiac arrhythmias, impaired cardiac conduction, respiratory depression, and disturbances of consciousness up to deep coma.

biotransformation

Hepatic. Maprotiline is metabolized by N-demethylation, deamination, aliphatic and aromatic hydroxylations and by formation of aromatic methoxy derivatives. It is slowly metabolized primarily to desmethylmaprotiline, a pharmacologically active metabolite. Desmethylmaprotiline may undergo further metabolism to maprotiline-N-oxide.

absorption

Slowly, but completely absorbed from the GI tract following oral administration.

half life

Average ~ 51 hours (range: 27-58 hours)

route of elimination

Approximately 60% of a single orally administered dose is excreted in urine as conjugated metabolites within 21 days; 30% is eliminated in feces.

drug interactions

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

Cisapride: Increased risk of cardiotoxicity and arrhythmias

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

Donepezil: Possible antagonism of action

Galantamine: Possible antagonism of action

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

Mesoridazine: Increased risk of cardiotoxicity and arrhythmias

Propranolol: Propranolol increases the serum levels of cisapride

Rivastigmine: Possible antagonism of action

Tacrine: The therapeutic effects of the central acetylcholinesterase inhibitor, Tacrine, and/or the anticholinergic, Maprotiline, 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 Maprotiline. Consider alternate therapy or monitor for therapeutic/adverse effects of Maprotiline if Terbinafine is initiated, discontinued or dose changed.

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

Tranylcypromine: Maprotiline may increase the adverse effects of the MAO inhibitor, Tranylcypromine. These agents should not be administered within 14 days of each other.

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

Trimethobenzamide: Trimethobenzamide and Maprotiline, 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 Maprotiline, 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 Maprotiline, 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 maprotiline, 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).