indication

May be used to treat obsessive-compulsive disorder and disorders with an obsessive-compulsive component (e.g. depression, schizophrenia, Tourette’s disorder). Unlabeled indications include: depression, panic disorder, chronic pain (e.g. central pain, idiopathic pain disorder, tension headache, diabetic peripheral neuropathy, neuropathic pain), cataplexy and associated narcolepsy (limited evidence), autistic disorder (limited evidence), trichotillomania (limited evidence), onchophagia (limited evidence), stuttering (limited evidence), premature ejaculation, and premenstrual syndrome.

pharmacology

Clomipramine, a tricyclic antidepressant, is the 3-chloro derivative of Imipramine. It was thought that tricyclic antidepressants work exclusively by inhibiting the re-uptake of the neurotransmitters norepinephrine and serotonin by nerve cells. However, this response occurs immediately, yet mood does not lift for around 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 desensitized (leading to increased noradrenaline production). Tricyclics are also known as effective analgesics for different types of pain, especially neuropathic or neuralgic pain.

mechanism of action

Clomipramine is a strong, but not completely selective serotonin reuptake inhibitor (SRI), as the active main metabolite desmethyclomipramine acts preferably as an inhibitor of noradrenaline reuptake. α₁-receptor blockage and β-down-regulation have been noted and most likely play a role in the short term effects of clomipramine. A blockade of sodium-channels and NDMA-receptors might, as with other tricyclics, account for its effect in chronic pain, in particular the neuropathic type.

toxicity

Signs and symptoms vary in severity depending upon factors such as the amount of drug absorbed, the age of the patient, and the time elapsed since drug ingestion. Critical manifestations of overdose include cardiac dysrhythmias, severe hypotension, convulsions, and CNS depression including coma. Changes in the electrocardiogram, particularly in QRS axis or width, are clinically significant indicators of tricyclic toxicity. In U.S. clinical trials, 2 deaths occurred in 12 reported cases of acute overdosage with Anafranil either alone or in combination with other drugs. One death involved a patient suspected of ingesting a dose of 7000 mg. The second death involved a patient suspected of ingesting a dose of 5750 mg. Side effects include: 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.

biotransformation

Extensively metabolized in the liver. The main active metabolite is desmethylclomipramine, which is formed by N-demethylation of clomipramine via CYP2C19, 3A4 and 1A2. Other metabolites and their glucuronide conjugates are also produced. Other metabolites of clomipramine include 8-hydroxyclomipramine formed via 8-hydroxylation, 2-hydroxyclomipramine formed via 2-hydroxylation, and clomipramine N-oxide formed by N-oxidation. Desmethylclomipramine is further metabolized to 8-hydroxydesmethylclomipramine and didesmethylclomipramine, which are formed by 8-hydroxylation and N-demethylation, respectively. 8-Hydroxyclomipramine and 8-hydroxydesmethylclomipramine are pharmacologically active; however, their clinical contribution remains unknown.

absorption

Well absorbed from the GI tract following oral administration. Bioavailability is approximately 50% orally due to extensive first-pass metabolism. Bioavailability is not affected by food. Peak plasma concentrations occur 2-6 hours following oral administration of a single 50 mg dose. Large interindividual variations in plasma concentrations occur, partly due to genetic differences in clomipramine metabolism. On average, steady state plasma concentrations are achieved in 1-2 weeks following multiple dose oral administration. Smoking appears to lower the steady-state plasma concentration of clomipramine, but not its active metabolite desmethylclomipramine.

half life

Following oral administration of a single 150 mg dose of clomipramine, the average elimination half-life of clomipramine was 32 hours (range: 19-37 hours) and of desmethylclomipramine was 69 hours (range: 54-77 hours). Elimination half-life may vary substantially with different doses due to probably saturable kinetics (i.e. metabolism).

route of elimination

Urine (51-60%) and feces via biliary elimination (24-32%)

drug interactions

Altretamine: Risk of severe hypotension

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

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

Butabarbital: Barbiturates like butabarbital may increase the metabolism of tricyclic antidepressants like clomipramine. 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 clomipramine. 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 the tricyclic antidepressant, clomipramine, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of clomipramine if cimetidine is initiated, discontinued or dose changed.

Cisapride: Increased risk of cardiotoxicity and arrhythmias

Clonidine: The tricyclic antidepressant, clomipramine, may decrease the effect of clonidine.

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

Dihydroquinidine barbiturate: Dihydroquinidine barbiturate increases the effect of the tricyclic antidepressant, clomipramine.

Dobutamine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of dobutamine.

Donepezil: Possible antagonism of action

Dopamine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of dopamine.

Ephedra: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of ephedra.

Ephedrine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of ephedrine.

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

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

Fluoxetine: The SSRI, fluoxetine, may increase the serum concentration of the tricyclic antidepressant, clomipramine, 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 clomipramine if fluoxetine is initiated, discontinued or dose changed.

Fluvoxamine: The SSRI, fluvoxamine, may increase the serum concentration of the tricyclic antidepressant, clomipramine, 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 clomipramine if fluvoxamine is initiated, discontinued or dose changed.

Galantamine: Possible antagonism of action

Grepafloxacin: Increased risk of cardiotoxicity and arrhythmias

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

Isocarboxazid: Possibility of severe adverse effects

Isoproterenol: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of isoproterenol.

Mephentermine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of mephentermine.

Metaraminol: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of metaraminol.

Methoxamine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of methoxamine.

Moclobemide: Possible severe adverse reaction with this combination

Norepinephrine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of norepinephrine.

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

Phenelzine: Possibility of severe adverse effects

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

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

Pirbuterol: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of pirbuterol.

Procaterol: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of procaterol.

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

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

Quinidine barbiturate: Quinidine barbiturate increases the effect of tricyclic antidepressant, clomipramine.

Rasagiline: Possibility of severe adverse effects

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

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

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

Rivastigmine: Possible antagonism of action

Salbutamol: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of salbutamol.

Sibutramine: Increased risk of CNS adverse effects

Sparfloxacin: Increased risk of cardiotoxicity and arrhythmias

Tacrine: The therapeutic effects of the central acetylcholinesterase inhibitor, Tacrine, and/or the anticholinergic, Clomipramine, 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.

Tamoxifen: Clomipramine may decrease the therapeutic effect of Tamoxifen by decreasing the production of active metabolites. Consider alternate therapy.

Tamsulosin: Clomipramine, a CYP2D6 inhibitor, may decrease the metabolism and clearance of Tamsulosin, a CYP2D6 substrate. Monitor for changes in therapeutic/adverse effects of Tamsulosin if Clomipramine is initiated, discontinued, or dose changed.

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

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

Terfenadine: Increased risk of cardiotoxicity and arrhythmias

Thiabendazole: The strong CYP1A2 inhibitor, Thiabendazole, may increase the effects and toxicity of Clomipramine by decreasing Clomipramine metabolism and clearance. Monitor for changes in the therapeutic and adverse effects of Clomipramine if Thiabendazole is initiated, discontinued or dose changed.

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.

Ticlopidine: Ticlopidine may decrease the metabolism and clearance of Clomipramine. Consider alternate therapy or monitor for adverse/toxic effects of Clomipramine if Ticlopidine is initiated, discontinued or dose changed.

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. Clomipramine may decrease the effect of Tramadol by decreasing active metabolite production.

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 Clomipramine, 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 Clomipramine, 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 Clomipramine, 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 clomipramine, 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).