PAROXETINE Drug Interactions: What You Need to Know

Drug Interactions Tryptophan As with other serotonin reuptake inhibitors, an interaction between paroxetine and tryptophan may occur when they are coadministered. Adverse experiences, consisting primarily of headache, nausea, sweating, and dizziness, have been reported when tryptophan was administered to patients taking paroxetine hydrochloride. Consequently, concomitant use of paroxetine hydrochloride with tryptophan is not recommended (see WARNINGS: Serotonin Syndrome ).

Monoamine Oxidase Inhibitors

See CONTRAINDICATIONS and WARNINGS . Pimozide In a controlled study of healthy volunteers, after paroxetine hydrochloride was titrated to 60 mg daily, coadministration of a single dose of 2 mg pimozide was associated with mean increases in pimozide AUC of 151% and C max of 62%, compared to pimozide administered alone. The increase in pimozide AUC and C max is due to the CYP2D6 inhibitory properties of paroxetine. Due to the narrow therapeutic index of pimozide and its known ability to prolong the QT interval, concomitant use of pimozide and paroxetine hydrochloride is contraindicated (see CONTRAINDICATIONS ).

Serotonergic Drugs

Based on the mechanism of action of SNRIs and SSRIs, including paroxetine hydrochloride and the potential for serotonin syndrome, caution is advised when paroxetine hydrochloride is coadministered with other drugs that may affect the serotonergic neurotransmitter systems, such as triptans, lithium, fentanyl, tramadol or St. John's Wort (see WARNINGS: Serotonin Syndrome ). The concomitant use of paroxetine hydrochloride with MAOIs (including linezolid and intravenous methylene blue) is contradicated (see CONTRADICATIONS ). The concomitant use of paroxetine hydrochloride with other SSRIs, SNRIs or tryptophan is not recommended (see PRECAUTIONS: Drug Interactions: Tryptophan ).

Thioridazine

See CONTRAINDICATIONS and WARNINGS .

Warfarin

Preliminary data suggest that there may be a pharmacodynamic interaction (that causes an increased bleeding diathesis in the face of unaltered prothrombin time) between paroxetine and warfarin. Since there is little clinical experience, the concomitant administration of paroxetine hydrochloride and warfarin should be undertaken with caution (see PRECAUTIONS: Information for Patients: Drugs That Interfere with Hemostasis ).

Triptans

There have been rare post-marketing reports of serotonin syndrome with the use of an SSRI and a triptan. If concomitant use of paroxetine hydrochloride with a triptan is clinically warranted, careful observation of the patient is advised, particularly during treatment initiation and dose increases (see WARNINGS: Serotonin Syndrome ).

Drugs Affecting Hepatic Metabolism

The metabolism and pharmacokinetics of paroxetine may be affected by the induction or inhibition of drug-metabolizing enzymes.

Cimetidine

Cimetidine inhibits many cytochrome P 450 (oxidative) enzymes. In a study where paroxetine hydrochloride (30 mg once daily) was dosed orally for 4 weeks, steady-state plasma concentrations of paroxetine were increased by approximately 50% during coadministration with oral cimetidine (300 mg three times daily) for the final week. Therefore, when these drugs are administered concurrently, dosage adjustment of paroxetine hydrochloride after the 20 mg starting dose should be guided by clinical effect. The effect of paroxetine on cimetidine’s pharmacokinetics was not studied.

Phenobarbital

Phenobarbital induces many cytochrome P 450 (oxidative) enzymes. When a single oral 30 mg dose of paroxetine hydrochloride was administered at phenobarbital steady-state (100 mg once daily for 14 days), paroxetine AUC and T 1/2 were reduced (by an average of 25% and 38%, respectively) compared to paroxetine administered alone. The effect of paroxetine on phenobarbital pharmacokinetics was not studied. Since paroxetine hydrochloride exhibits nonlinear pharmacokinetics, the results of this study may not address the case where the two drugs are both being chronically dosed. No initial dosage adjustment of paroxetine hydrochloride is considered necessary when coadministered with phenobarbital; any subsequent adjustment should be guided by clinical effect.

Phenytoin

When a single oral 30 mg dose of paroxetine hydrochloride was administered at phenytoin steady-state (300 mg once daily for 14 days), paroxetine AUC and T 1/2 were reduced (by an average of 50% and 35%, respectively) compared to paroxetine hydrochloride administered alone. In a separate study, when a single oral 300 mg dose of phenytoin was administered at paroxetine steady-state (30 mg once daily for 14 days), phenytoin AUC was slightly reduced (12% on average) compared to phenytoin administered alone. Since both drugs exhibit nonlinear pharmacokinetics, the above studies may not address the case where the two drugs are both being chronically dosed. No initial dosage adjustments are considered necessary when these drugs are coadministered; any subsequent adjustments should be guided by clinical effect (see ADVERSE REACTIONS: Post-Marketing Reports ).

Drugs

Metabolized by CYP2D6 Many drugs, including most drugs effective in the treatment of major depressive disorder (paroxetine, other SSRIs and many tricyclics), are metabolized by the cytochrome P 450 isozyme CYP2D6. Like other agents that are metabolized by CYP2D6, paroxetine may significantly inhibit the activity of this isozyme. In most patients (> 90%), this CYP2D6 isozyme is saturated early during dosing with paroxetine hydrochloride. In one study, daily dosing of paroxetine hydrochloride (20 mg once daily) under steady-state conditions increased single dose desipramine (100 mg) C max , AUC, and T 1/2 by an average of approximately 2-, 5-, and 3-fold, respectively. Concomitant use of paroxetine with risperidone, a CYP2D6 substrate has also been evaluated. In one study, daily dosing of paroxetine 20 mg in patients stabilized on risperidone (4 to 8 mg/day) increased mean plasma concentrations of risperidone approximately 4-fold, decreased 9-hydroxyrisperidone concentrations approximately 10%, and increased concentrations of the active moiety (the sum of risperidone plus 9-hydroxyrisperidone) approximately 1.4-fold. The effect of paroxetine on the pharmacokinetics of atomoxetine has been evaluated when both drugs were at steady-state. In healthy volunteers who were extensive metabolizers of CYP2D6, paroxetine 20 mg daily was given in combination with 20 mg atomoxetine every 12 hours. This resulted in increases in steady-state atomoxetine AUC values that were 6- to 8-fold greater and in atomoxetine C max values that were 3- to 4-fold greater than when atomoxetine was given alone. Dosage adjustment of atomoxetine may be necessary and it is recommended that atomoxetine be initiated at a reduced dose when it is given with paroxetine. Concomitant use of paroxetine hydrochloride with other drugs metabolized by cytochrome CYP2D6 has not been formally studied but may require lower doses than usually prescribed for either paroxetine hydrochloride or the other drug. Therefore, coadministration of paroxetine hydrochloride with other drugs that are metabolized by this isozyme, including certain drugs effective in the treatment of major depressive disorder (e.g., nortriptyline, amitriptyline, imipramine, desipramine, and fluoxetine), phenothiazines, risperidone and Type 1C antiarrhythmics (e.g., propafenone, flecainide, and encainide), or that inhibit this enzyme (e.g., quinidine), should be approached with caution. However, due to the risk of serious ventricular arrhythmias and sudden death potentially associated with elevated plasma levels of thioridazine, paroxetine and thioridazine should not be coadministered (see CONTRAINDICATIONS and WARNINGS ). Tamoxifen is a pro-drug requiring metabolic activation by CYP2D6. Inhibition of CYP2D6 by paroxetine may lead to reduced plasma concentrations of an active metabolite (endoxifen) and hence reduced efficacy of tamoxifen (see PRECAUTIONS ). At steady-state, when the CYP2D6 pathway is essentially saturated, paroxetine clearance is governed by alternative P 450 isozymes that, unlike CYP2D6, show no evidence of saturation (see PRECAUTIONS: Drug Interactions: Tricyclic Antidepressants (TCAs) ).

Drugs

Metabolized by Cytochrome CYP3A4 An in vivo interaction study involving the coadministration under steady-state conditions of paroxetine and terfenadine, a substrate for cytochrome CYP3A4, revealed no effect of paroxetine on terfenadine pharmacokinetics. In addition, in vitro studies have shown ketoconazole, a potent inhibitor of CYP3A4 activity, to be at least 100 times more potent than paroxetine as an inhibitor of the metabolism of several substrates for this enzyme, including terfenadine, astemizole, cisapride, triazolam, and cyclosporine. Based on the assumption that the relationship between paroxetine’s in vitro K i and its lack of effect on terfenadine’s in vivo clearance predicts its effect on other CYP3A4 substrates, paroxetine’s extent of inhibition of CYP3A4 activity is not likely to be of clinical significance.

Tricyclic

Antidepressants (TCAs) Caution is indicated in the coadministration of tricyclic antidepressants (TCAs) with paroxetine hydrochloride, because paroxetine may inhibit TCA metabolism. Plasma TCA concentrations may need to be monitored, and the dose of TCA may need to be reduced, if a TCA is coadministered with paroxetine hydrochloride (see PRECAUTIONS: Drugs Metabolized by Cytochrome CYP2D6 ).

Drugs Highly

Bound to Plasma Protein Because paroxetine is highly bound to plasma protein, administration of paroxetine hydrochloride to a patient taking another drug that is highly protein bound may cause increased free concentrations of the other drug, potentially resulting in adverse events. Conversely, adverse effects could result from displacement of paroxetine by other highly bound drugs.

Drugs That

Interfere with Hemostasis (e.g., NSAIDs, Aspirin and Warfarin) Serotonin release by platelets plays an important role in hemostasis. Epidemiological studies of the case control and cohort design that have demonstrated an association between use of psychotropic drugs that interfere with serotonin reuptake and the occurrence of upper gastrointestinal bleeding have also shown that concurrent use of an NSAID or aspirin may potentiate this risk of bleeding. Altered anticoagulant effects, including increased bleeding, have been reported when SSRIs or SNRIs are coadministered with warfarin. Patients receiving warfarin therapy should be carefully monitored when paroxetine is initiated or discontinued.

Alcohol

Although paroxetine hydrochloride does not increase the impairment of mental and motor skills caused by alcohol, patients should be advised to avoid alcohol while taking paroxetine hydrochloride. Lithium A multiple-dose study has shown that there is no pharmacokinetic interaction between paroxetine hydrochloride and lithium carbonate. However, due to the potential for serotonin syndrome, caution is advised when paroxetine hydrochloride is coadministered with lithium.

Digoxin

The steady-state pharmacokinetics of paroxetine was not altered when administered with digoxin at steady-state. Mean digoxin AUC at steady-state decreased by 15% in the presence of paroxetine. Since there is little clinical experience, the concurrent administration of paroxetine and digoxin should be undertaken with caution.

Diazepam

Under steady-state conditions, diazepam does not appear to affect paroxetine kinetics. The effects of paroxetine on diazepam were not evaluated.

Procyclidine

Daily oral dosing of paroxetine tablets (30 mg once daily) increased steady-state AUC 0-24 , C max , and C min values of procyclidine (5 mg oral once daily) by 35%, 37%, and 67%, respectively, compared to procyclidine alone at steady-state. If anticholinergic effects are seen, the dose of procyclidine should be reduced. Beta-Blockers In a study where propranolol (80 mg twice daily) was dosed orally for 18 days, the established steady-state plasma concentrations of propranolol were unaltered during coadministration with paroxetine hydrochloride (30 mg once daily) for the final 10 days. The effects of propranolol on paroxetine have not been evaluated (see ADVERSE REACTIONS: Post-Marketing Reports ).

Theophylline

Reports of elevated theophylline levels associated with treatment with paroxetine hydrochloride have been reported. While this interaction has not been formally studied, it is recommended that theophylline levels be monitored when these drugs are concurrently administered.

Fosamprenavir/Ritonavir

Coadministration of fosamprenavir/ritonavir with paroxetine significantly decreased plasma levels of paroxetine. Any dose adjustment should be guided by clinical effect (tolerability and efficacy).

Electroconvulsive

Therapy (ECT) There are no clinical studies of the combined use of ECT and paroxetine hydrochloride.

4 CONTRAINDICATIONS

• Concurrent use with monoamine oxidase inhibitors (MAOI) or use within 14 days of MAOI use ( 2.2 , 4.1 , 5.2 , 7.3 )
• Use with thioridazine ( 4.2 , 7.1 )
• Use with pimozide ( 4.3 , 7.1 )
• Hypersensitivity to any ingredient in paroxetine capsules ( 4.4 )
• Pregnancy ( 4.5 , 8.1 )

4.1 Monoamine Oxidase Inhibitors Concomitant use of an MAOI with paroxetine capsules or within 14 days of stopping treatment with paroxetine capsules is contraindicated because of an increased risk of serotonin syndrome. The use of paroxetine capsules within 14 days of stopping an MAOI is also contraindicated <span class="opacity-50 text-xs">[see Dosage and Administration (2.2), Warnings and Precautions (5.2) and Drug Interactions (7.3)]</span> . Starting paroxetine capsules in a patient who is being treated with linezolid or intravenous methylene blue, both of which inhibit monoamine oxidase, is also contraindicated because of an increased risk of serotonin syndrome <span class="opacity-50 text-xs">[see Dosage and Administration (2.2), Warnings and Precautions (5.2) and Drug Interactions (7.3)]</span> .

4.2 Thioridazine Concomitant use of paroxetine capsules with thioridazine is contraindicated, because thioridazine prolongs the QT interval, and paroxetine can increase thioridazine levels <span class="opacity-50 text-xs">[see Drug Interactions (7.1)]</span> .

4.3 Pimozide Concomitant use of paroxetine capsules with pimozide is contraindicated because pimozide prolongs the QT interval, and paroxetine increases pimozide levels <span class="opacity-50 text-xs">[see Drug Interactions (7.1)]</span> .

4.4 Hypersensitivity to any Ingredient in Paroxetine Capsules Paroxetine capsules are contraindicated in patients with a history of hypersensitivity to paroxetine or any of the other ingredients in paroxetine capsules.

4.5 Pregnancy Menopausal VMS does not occur during pregnancy and paroxetine capsules may cause fetal harm <span class="opacity-50 text-xs">[see Use in Specific Populations (8.1)]</span>.

5 ​WARNINGS AND PRECAUTIONS Serotonin Syndrome : Increased risk when co-administered with other serotonergic agents (e.g., SSRI, SNRI, triptans), but also when taken alone. If occurs, discontinue paroxetine and initiate supportive measures. (5.2) Embryofetal and Neonatal Toxicity : Can cause fetal and neonatal harm. Increased risk of cardiovascular malformations with exposure during the first trimester. Exposure in late pregnancy may lead to an increased risk for persistent pulmonary hypertension of the newborn. (5.4, 8.1)

Increased

Risk of Bleeding : Concomitant use of aspirin, nonsteroidal anti- inflammatory drugs, other antiplatelet drugs, warfarin, and other anticoagulant drugs may increase risk. (5.5) Activation of Mania/Hypomania : Screen patients for bipolar disorder. (5.6) Seizures : Use with caution in patients with seizure disorders. (5.8) Angle-Closure Glaucoma : Angle-closure glaucoma has occurred in patients with untreated anatomically narrow angles treated with antidepressants. (5.9)

Sexual

Dysfunction : Paroxetine may cause symptoms of sexual dysfunction. (5.13) 5.1 ​Suicidal Thoughts and Behaviors in Adolescents and Young Adults In pooled analyses of placebo-controlled trials of antidepressant drugs (SSRIs and other antidepressant classes) that included approximately 77,000 adult patients and 4,500 pediatric patients, the incidence of suicidal thoughts and behaviors in antidepressant-treated patients age 24 years and younger was greater than in placebo-treated patients. There was considerable variation in risk of suicidal thoughts and behaviors among drugs, but there was an increased risk identified in young patients for most drugs studied. There were differences in absolute risk of suicidal thoughts and behaviors across the different indications, with the highest incidence in patients with MDD. The drug-placebo differences in the number of cases of suicidal thoughts and behaviors per 1000 patients treated are provided in Table 2.

Table

2: Risk Differences of the Number of Patients with Suicidal Thoughts and Behaviors in the Pooled Placebo-Controlled Trials of Antidepressants in Pediatric and Adult Patients Age Range Drug-Placebo Difference in Number of Patients with Suicidal Thoughts and Behaviors per 1,000 Patients Treated Increases Compared to Placebo <18 years old 14 additional cases 18-24 years old 5 additional cases Decreases Compared to Placebo 25-64 years old 1 fewer case ≥65 years old 6 fewer cases Paroxetine is not approved for use in pediatric patients. It is unknown whether the risk of suicidal thoughts and behaviors in children, adolescents, and young adults extends to longer-term use, i.e., beyond four months. However, there is substantial evidence from placebo-controlled maintenance trials in adults with MDD that antidepressants delay the recurrence of depression and that depression itself is a risk factor for suicidal thoughts and behaviors. Monitor all antidepressant-treated patients for any indication for clinical worsening and emergence of suicidal thoughts and behaviors, especially during the initial few months of drug therapy, and at times of dosage changes. Counsel family members or caregivers of patients to monitor for changes in behavior and to alert the healthcare provider. Consider changing the therapeutic regimen, including possibly discontinuing paroxetine, in patients whose depression is persistently worse, or who are experiencing emergent suicidal thoughts or behaviors.

5.2 Serotonin Syndrome SSRIs, including paroxetine, can precipitate serotonin syndrome, a potentially life-threatening condition. The risk is increased with concomitant use of other serotonergic drugs (including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, meperidine, methadone, tryptophan, buspirone, amphetamines and St. John’s Wort) and with drugs that impair metabolism of serotonin, i.e., MAOIs <span class="opacity-50 text-xs">[see Contraindications (4), Drug Interactions (7.1)]</span> . Serotonin syndrome can also occur when these drugs are used alone. Serotonin syndrome symptoms may include mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, and/or gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). The concomitant use of paroxetine with MAOIs is contraindicated. In addition, do not initiate paroxetine in a patient being treated with MAOIs such as linezolid or intravenous methylene blue. No reports involved the administration of methylene blue by other routes (such as oral tablets or local tissue injection) or at lower doses. If it is necessary to initiate treatment with an MAOI such as linezolid or intravenous methylene blue in a patient taking paroxetine discontinue paroxetine before initiating treatment with the MAOI <span class="opacity-50 text-xs">[see Contraindications (4), Drug Interactions (7)]</span> . Monitor all patients taking paroxetine for the emergence of serotonin syndrome. Discontinue treatment with paroxetine and any concomitant serotonergic agents immediately if the above symptoms occur, and initiate supportive symptomatic treatment. If concomitant use of paroxetine with other serotonergic drugs is clinically warranted, inform patients of the increased risk for serotonin syndrome and monitor for symptoms. 5.3 ​Drug Interactions Leading to QT Prolongation The CYP2D6 inhibitory properties of paroxetine can elevate plasma levels of thioridazine and pimozide. Since thioridazine and pimozide given alone produce prolongation of the QTc interval and increase the risk of serious ventricular arrhythmias, the use of paroxetine is contraindicated in combination with thioridazine and pimozide <span class="opacity-50 text-xs">[see Contraindications (4), Drug Interactions (7), Clinical Pharmacology (12.3)]</span>. 5.4 ​Embryofetal and Neonatal Toxicity Paroxetine can cause fetal harm when administered to a pregnant woman. Epidemiological studies have shown that infants exposed to paroxetine in the first trimester of pregnancy have an increased risk of cardiovascular malformations. Exposure to paroxetine in late pregnancy may lead to an increased risk for persistent pulmonary hypertension of the newborn (PPNH) and/or neonatal complications requiring prolonged hospitalization, respiratory support, and tube feeding. If paroxetine are used during pregnancy, or if the patient becomes pregnant while taking paroxetine, the patient should be apprised of the potential hazard to the fetus <span class="opacity-50 text-xs">[see Use in Specific Populations (8.1)]</span>. 5.5 ​ Increased Risk of Bleeding Drugs that interfere with serotonin reuptake inhibition, including paroxetine, increase the risk of bleeding events. Concomitant use of aspirin, nonsteroidal anti-inflammatory drugs (NSAIDS), other antiplatelet drugs, warfarin, and other anticoagulants may add to this risk. Case reports and epidemiological studies (case-control and cohort design) have demonstrated an association between use of drugs that interfere with serotonin reuptake and the occurrence of gastrointestinal bleeding. Based on data from the published observational studies, exposure to SSRIs, particularly in the month before delivery, has been associated with a less than 2-fold increase in the risk of postpartum hemorrhage <span class="opacity-50 text-xs">[see Use in Specific Populations (8.1)]</span>. Bleeding events related to drugs that interfere with serotonin reuptake have ranged from ecchymoses, hematomas, epistaxis, and petechiae to life-threatening hemorrhages. Inform patients about the increased risk of bleeding associated with the concomitant use of paroxetine and antiplatelet agents or anticoagulants. For patients taking warfarin, carefully monitor the international normalized ratio. 5.6 ​Activation of Mania or Hypomania In patients with bipolar disorder, treating a depressive episode with paroxetine or another antidepressant may precipitate a mixed/manic episode. During controlled clinical trials of paroxetine, hypomania or mania occurred in approximately 1% of paroxetine-treated unipolar patients compared to 1.1% of active-control and 0.3% of placebo-treated unipolar patients. Prior to initiating treatment with paroxetine, screen patients for any personal or family history of bipolar disorder, mania, or hypomania. 5.7 ​Discontinuation Syndrome Adverse reactions after discontinuation of serotonergic antidepressants, particularly after abrupt discontinuation, include: nausea, sweating, dysphoric mood, irritability, agitation, dizziness, sensory disturbances (e.g., paresthesia, such as electric shock sensations), tremor, anxiety, confusion, headache, lethargy, emotional lability, insomnia, hypomania, tinnitus, and seizures. A gradual reduction in dosage rather than abrupt cessation is recommended whenever possible <span class="opacity-50 text-xs">[see Dosage and Administration (2.7)]</span>. During clinical trials of GAD and PTSD, gradual decreases in the daily dose by 10 mg/day at weekly intervals followed by 1 week at 20 mg/day was used before treatment was discontinued. The following adverse reactions were reported at an incidence of 2% or greater for paroxetine and were at least twice that reported for placebo: Abnormal dreams, paresthesia, and dizziness Adverse reactions have been reported upon discontinuation of treatment with paroxetine in pediatric patients. The safety and effectiveness of paroxetine in pediatric patients have not been established <span class="opacity-50 text-xs">[see Boxed Warning, Warnings and Precautions (5.1), Use in Specific Populations (8.4)]</span>. 5.8 ​Seizures Paroxetine tablets have not been systematically evaluated in patients with seizure disorders. Patients with history of seizures were excluded from clinical studies. During clinical studies, seizures occurred in 0.1% of patients treated with paroxetine. Paroxetine should be prescribed with caution in patients with a seizure disorder. Discontinue paroxetine in any patient who develops seizures. 5.9 ​Angle-Closure Glaucoma The pupillary dilation that occurs following use of many antidepressant drugs including paroxetine may trigger an angle closure attack in a patient with anatomically narrow angles who does not have a patent iridectomy. Cases of angle-closure glaucoma associated with use of paroxetine have been reported. Avoid use of antidepressants, including paroxetine in patients with untreated anatomically narrow angles. 5.10 ​Hyponatremia Hyponatremia may occur as a result of treatment with SSRIs, including paroxetine. Cases with serum sodium lower than 110mmol/L have been reported. Signs and symptoms of hyponatremia include headache, difficulty concentrating, memory impairment, confusion, weakness, and unsteadiness, which may lead to falls. Signs and symptoms associated with more severe and/or acute cases have included hallucination, syncope, seizure, coma, respiratory arrest, and death. In many cases, this hyponatremia appears to be the result of the syndrome of inappropriate antidiuretic hormone secretion (SIADH). In patients with symptomatic hyponatremia, discontinue paroxetine and institute appropriate medical intervention. Elderly patients, patients taking diuretics, and those who are volume-depleted may be at greater risk of developing hyponatremia with SSRIs <span class="opacity-50 text-xs">[see Use in Specific Populations (8.5)]</span>. 5.11 ​Reduction of Efficacy of Tamoxifen Some studies have shown that the efficacy of tamoxifen, as measured by the risk of breast cancer relapse/mortality, may be reduced with concomitant use of paroxetine as a result of paroxetine’s irreversible inhibition of CYP2D6 and lower blood levels of tamoxifen <span class="opacity-50 text-xs">[see Drug Interactions (7)]</span> . One study suggests that the risk may increase with longer duration of coadministration. However, other studies have failed to demonstrate such a risk. When tamoxifen is used for the treatment or prevention of breast cancer, prescribers should consider using an alternative antidepressant with little or no CYP2D6 inhibition. 5.12 ​Bone Fracture Epidemiological studies on bone fracture risk during exposure to some antidepressants, including SSRIs, have reported an association between antidepressant treatment and fractures. There are multiple possible causes for this observation, and it is unknown to what extent fracture risk is directly attributable to SSRI treatment. 5.13 ​Sexual Dysfunction Use of SSRIs, including paroxetine, may cause symptoms of sexual dysfunction <span class="opacity-50 text-xs">[see Adverse Reactions (6.1)]</span> . In male patients, SSRI use may result in ejaculatory delay or failure, decreased libido, and erectile dysfunction. In female patients, SSRI use may result in decreased libido and delayed or absent orgasm. It is important for prescribers to inquire about sexual function prior to initiation of paroxetine and to inquire specifically about changes in sexual function during treatment, because sexual function may not be spontaneously reported. When evaluating changes in sexual function, obtaining a detailed history (including timing of symptom onset) is important because sexual symptoms may have other causes, including the underlying psychiatric disorder. Discuss potential management strategies to support patients in making informed decisions about treatment.

5.1 ​Suicidal Thoughts and Behaviors in Adolescents and Young Adults In pooled analyses of placebo-controlled trials of antidepressant drugs (SSRIs and other antidepressant classes) that included approximately 77,000 adult patients and 4,500 pediatric patients, the incidence of suicidal thoughts and behaviors in antidepressant-treated patients age 24 years and younger was greater than in placebo-treated patients. There was considerable variation in risk of suicidal thoughts and behaviors among drugs, but there was an increased risk identified in young patients for most drugs studied. There were differences in absolute risk of suicidal thoughts and behaviors across the different indications, with the highest incidence in patients with MDD. The drug-placebo differences in the number of cases of suicidal thoughts and behaviors per 1000 patients treated are provided in Table 2.

Table

2: Risk Differences of the Number of Patients with Suicidal Thoughts and Behaviors in the Pooled Placebo-Controlled Trials of Antidepressants in Pediatric and Adult Patients Age Range Drug-Placebo Difference in Number of Patients with Suicidal Thoughts and Behaviors per 1,000 Patients Treated Increases Compared to Placebo <18 years old 14 additional cases 18-24 years old 5 additional cases Decreases Compared to Placebo 25-64 years old 1 fewer case ≥65 years old 6 fewer cases Paroxetine is not approved for use in pediatric patients. It is unknown whether the risk of suicidal thoughts and behaviors in children, adolescents, and young adults extends to longer-term use, i.e., beyond four months. However, there is substantial evidence from placebo-controlled maintenance trials in adults with MDD that antidepressants delay the recurrence of depression and that depression itself is a risk factor for suicidal thoughts and behaviors. Monitor all antidepressant-treated patients for any indication for clinical worsening and emergence of suicidal thoughts and behaviors, especially during the initial few months of drug therapy, and at times of dosage changes. Counsel family members or caregivers of patients to monitor for changes in behavior and to alert the healthcare provider. Consider changing the therapeutic regimen, including possibly discontinuing paroxetine, in patients whose depression is persistently worse, or who are experiencing emergent suicidal thoughts or behaviors.

5.2 Serotonin Syndrome SSRIs, including paroxetine, can precipitate serotonin syndrome, a potentially life-threatening condition. The risk is increased with concomitant use of other serotonergic drugs (including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, meperidine, methadone, tryptophan, buspirone, amphetamines and St. John’s Wort) and with drugs that impair metabolism of serotonin, i.e., MAOIs <span class="opacity-50 text-xs">[see Contraindications (4), Drug Interactions (7.1)]</span> . Serotonin syndrome can also occur when these drugs are used alone. Serotonin syndrome symptoms may include mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, and/or gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). The concomitant use of paroxetine with MAOIs is contraindicated. In addition, do not initiate paroxetine in a patient being treated with MAOIs such as linezolid or intravenous methylene blue. No reports involved the administration of methylene blue by other routes (such as oral tablets or local tissue injection) or at lower doses. If it is necessary to initiate treatment with an MAOI such as linezolid or intravenous methylene blue in a patient taking paroxetine discontinue paroxetine before initiating treatment with the MAOI <span class="opacity-50 text-xs">[see Contraindications (4), Drug Interactions (7)]</span> . Monitor all patients taking paroxetine for the emergence of serotonin syndrome. Discontinue treatment with paroxetine and any concomitant serotonergic agents immediately if the above symptoms occur, and initiate supportive symptomatic treatment. If concomitant use of paroxetine with other serotonergic drugs is clinically warranted, inform patients of the increased risk for serotonin syndrome and monitor for symptoms.

5.3 ​Drug Interactions Leading to QT Prolongation The CYP2D6 inhibitory properties of paroxetine can elevate plasma levels of thioridazine and pimozide. Since thioridazine and pimozide given alone produce prolongation of the QTc interval and increase the risk of serious ventricular arrhythmias, the use of paroxetine is contraindicated in combination with thioridazine and pimozide [see Contraindications (4), Drug Interactions (7), Clinical Pharmacology (12.3)].

5.4 ​Embryofetal and Neonatal Toxicity Paroxetine can cause fetal harm when administered to a pregnant woman. Epidemiological studies have shown that infants exposed to paroxetine in the first trimester of pregnancy have an increased risk of cardiovascular malformations. Exposure to paroxetine in late pregnancy may lead to an increased risk for persistent pulmonary hypertension of the newborn (PPNH) and/or neonatal complications requiring prolonged hospitalization, respiratory support, and tube feeding. If paroxetine are used during pregnancy, or if the patient becomes pregnant while taking paroxetine, the patient should be apprised of the potential hazard to the fetus [see Use in Specific Populations (8.1)].

5.5 ​ Increased Risk of Bleeding Drugs that interfere with serotonin reuptake inhibition, including paroxetine, increase the risk of bleeding events. Concomitant use of aspirin, nonsteroidal anti-inflammatory drugs (NSAIDS), other antiplatelet drugs, warfarin, and other anticoagulants may add to this risk. Case reports and epidemiological studies (case-control and cohort design) have demonstrated an association between use of drugs that interfere with serotonin reuptake and the occurrence of gastrointestinal bleeding. Based on data from the published observational studies, exposure to SSRIs, particularly in the month before delivery, has been associated with a less than 2-fold increase in the risk of postpartum hemorrhage [see Use in Specific Populations (8.1)]. Bleeding events related to drugs that interfere with serotonin reuptake have ranged from ecchymoses, hematomas, epistaxis, and petechiae to life-threatening hemorrhages. Inform patients about the increased risk of bleeding associated with the concomitant use of paroxetine and antiplatelet agents or anticoagulants. For patients taking warfarin, carefully monitor the international normalized ratio.

5.6 ​Activation of Mania or Hypomania In patients with bipolar disorder, treating a depressive episode with paroxetine or another antidepressant may precipitate a mixed/manic episode. During controlled clinical trials of paroxetine, hypomania or mania occurred in approximately 1% of paroxetine-treated unipolar patients compared to 1.1% of active-control and 0.3% of placebo-treated unipolar patients. Prior to initiating treatment with paroxetine, screen patients for any personal or family history of bipolar disorder, mania, or hypomania.

5.7 ​Discontinuation Syndrome Adverse reactions after discontinuation of serotonergic antidepressants, particularly after abrupt discontinuation, include: nausea, sweating, dysphoric mood, irritability, agitation, dizziness, sensory disturbances (e.g., paresthesia, such as electric shock sensations), tremor, anxiety, confusion, headache, lethargy, emotional lability, insomnia, hypomania, tinnitus, and seizures. A gradual reduction in dosage rather than abrupt cessation is recommended whenever possible [see Dosage and Administration (2.7)]. During clinical trials of GAD and PTSD, gradual decreases in the daily dose by 10 mg/day at weekly intervals followed by 1 week at 20 mg/day was used before treatment was discontinued. The following adverse reactions were reported at an incidence of 2% or greater for paroxetine and were at least twice that reported for placebo: Abnormal dreams, paresthesia, and dizziness Adverse reactions have been reported upon discontinuation of treatment with paroxetine in pediatric patients. The safety and effectiveness of paroxetine in pediatric patients have not been established [see Boxed Warning, Warnings and Precautions (5.1), Use in Specific Populations (8.4)].

5.8 ​Seizures Paroxetine tablets have not been systematically evaluated in patients with seizure disorders. Patients with history of seizures were excluded from clinical studies. During clinical studies, seizures occurred in 0.1% of patients treated with paroxetine. Paroxetine should be prescribed with caution in patients with a seizure disorder. Discontinue paroxetine in any patient who develops seizures.

5.9 ​Angle-Closure Glaucoma The pupillary dilation that occurs following use of many antidepressant drugs including paroxetine may trigger an angle closure attack in a patient with anatomically narrow angles who does not have a patent iridectomy. Cases of angle-closure glaucoma associated with use of paroxetine have been reported. Avoid use of antidepressants, including paroxetine in patients with untreated anatomically narrow angles.

5.10 ​Hyponatremia Hyponatremia may occur as a result of treatment with SSRIs, including paroxetine. Cases with serum sodium lower than 110mmol/L have been reported. Signs and symptoms of hyponatremia include headache, difficulty concentrating, memory impairment, confusion, weakness, and unsteadiness, which may lead to falls. Signs and symptoms associated with more severe and/or acute cases have included hallucination, syncope, seizure, coma, respiratory arrest, and death. In many cases, this hyponatremia appears to be the result of the syndrome of inappropriate antidiuretic hormone secretion (SIADH). In patients with symptomatic hyponatremia, discontinue paroxetine and institute appropriate medical intervention. Elderly patients, patients taking diuretics, and those who are volume-depleted may be at greater risk of developing hyponatremia with SSRIs [see Use in Specific Populations (8.5)].

5.11 ​Reduction of Efficacy of Tamoxifen Some studies have shown that the efficacy of tamoxifen, as measured by the risk of breast cancer relapse/mortality, may be reduced with concomitant use of paroxetine as a result of paroxetine’s irreversible inhibition of CYP2D6 and lower blood levels of tamoxifen [see Drug Interactions (7)] . One study suggests that the risk may increase with longer duration of coadministration. However, other studies have failed to demonstrate such a risk. When tamoxifen is used for the treatment or prevention of breast cancer, prescribers should consider using an alternative antidepressant with little or no CYP2D6 inhibition.

5.12 ​Bone Fracture Epidemiological studies on bone fracture risk during exposure to some antidepressants, including SSRIs, have reported an association between antidepressant treatment and fractures. There are multiple possible causes for this observation, and it is unknown to what extent fracture risk is directly attributable to SSRI treatment.

5.13 ​Sexual Dysfunction Use of SSRIs, including paroxetine, may cause symptoms of sexual dysfunction [see Adverse Reactions (6.1)] . In male patients, SSRI use may result in ejaculatory delay or failure, decreased libido, and erectile dysfunction. In female patients, SSRI use may result in decreased libido and delayed or absent orgasm. It is important for prescribers to inquire about sexual function prior to initiation of paroxetine and to inquire specifically about changes in sexual function during treatment, because sexual function may not be spontaneously reported. When evaluating changes in sexual function, obtaining a detailed history (including timing of symptom onset) is important because sexual symptoms may have other causes, including the underlying psychiatric disorder. Discuss potential management strategies to support patients in making informed decisions about treatment.