Clinical drug

fluoxetine 20 MG Oral Capsule [Prozac]

20 MG · Oral Capsule · oral

A form of fluoxetine

fluoxetine 20 MG Oral Capsule [Prozac] — Selective serotonin reuptake inhibitors. INDICATIONS AND USAGE Fluoxetine capsules, USP are a selective serotonin reuptake inhibitor indicated for: • Acute and maintenance treatment of Major

fluoxetine 20 MG Oral Capsule [Prozac]

Boxed warning

WARNING: SUICIDAL THOUGHTS AND BEHAVIORS • Antidepressants increased the risk of suicidal thoughts and behavior in children, adolescents, and young adults in short-term studies. These studies did not show an increase in the risk of suicidal thoughts and behavior with antidepressant use in patients over age 24; there was a reduction in risk with antidepressant use in patients aged 65 and older [see Warnings and Precautions (5.1) ] . • In patients of all ages who are started on antidepressant therapy, monitor closely for worsening and for emergence of suicidal thoughts and behaviors. Advise families and caregivers of the need for close observation and communication with the prescriber [see Warnings and Precautions (5.1) ] . • Fluoxetine is not approved for use in children less than 7 years of age [see Warnings and Precautions (5.1) and Use in Specific Populations (8.4) ] . When using fluoxetine and olanzapine in combination, also refer to Boxed Warning section of the package insert for Symbyax. WARNING: SUICIDAL THOUGHTS AND BEHAVIORS See full prescribing information for complete boxed warning. • Increased risk of suicidal thinking and behavior in children, adolescents, and young adults taking antidepressants ( 5.1 ). • Monitor for worsening and emergence of suicidal thoughts and behaviors ( 5.1 ). When using fluoxetine and olanzapine in combination, also refer to Boxed Warning section of the package insert for Symbyax. If you take fluoxetine capsules, you should not take any other medicines that contain fluoxetine hydrochloride including : 1. Symbyax 2. Sarafem 3. Prozac Weekly

Active ingredient

Classification

Selective serotonin reuptake inhibitorsSerotonin Reuptake Inhibitor

Drug interactions

Fluoxetine has several documented drug interactions that may affect its efficacy and safety.

  • majorMonoamine Oxidase Inhibitors (MAOIs) — Risk of serious adverse effects
  • majorCYP2D6 substrates — Increased plasma levels of drugs metabolized by CYP2D6
  • moderateTricyclic Antidepressants (TCAs) — Altered TCA levels
  • moderateCNS Acting Drugs — Potential for increased CNS effects
  • moderateBenzodiazepines (e.g., Diazepam, Alprazolam) — Increased half-life and psychomotor performance decrement
  • moderateAntipsychotics (e.g., Haloperidol, Clozapine) — Potential elevation of antipsychotic levels
  • moderateAnticonvulsants (e.g., Phenytoin, Carbamazepine) — Potential for elevated levels and toxicity
  • majorDrugs that Interfere with Hemostasis (e.g., NSAIDs, Aspirin, Warfarin) — Increased risk of bleeding
  • majorPimozide — Increased risk of QT prolongation
  • majorThioridazine — Increased risk of QT prolongation

Indications

INDICATIONS AND USAGE Fluoxetine capsules, USP are a selective serotonin reuptake inhibitor indicated for: • Acute and maintenance treatment of Major Depressive Disorder (MDD) in adult and pediatric patients aged 8 to 18 years (1.1) • Acute and maintenance treatment of Obsessive Compulsive Disorder (OCD) in adult and pediatric patients aged 7 to 17 years (1.2) • Acute and maintenance treatment of Bulimia Nervosa in adult patients (1.3) • Acute treatment of Panic Disorder, with or without agoraphobia, in adult patients (1.4) Fluoxetine capsules, USP and olanzapine in combination for: • Acute treatment of Depressive Episodes Associated with Bipolar I Disorder (1.5) 1.1 Major Depressive Disorder Fluoxetine capsules, USP are indicated for the acute and maintenance treatment of Major Depressive Disorder in adult patients and in pediatric patients aged 8 to 18 years [see Clinical Studies (14.1) ]. The usefulness of the drug in adult and pediatric patients receiving fluoxetine for extended periods, should periodically be re-evaluated [see Dosage and Administration (2.1) ] . 1.2 Obsessive Compulsive Disorder Fluoxetine capsules, USP are indicated for the acute and maintenance treatment of obsessions and compulsions in adult patients and in pediatric patients aged 7 to 17 years with Obsessive Compulsive Disorder (OCD) [see Clinical Studies (14.2) ]. The effectiveness of fluoxetine capsules, USP in long-term use, i.e., for more than 13 weeks, has not been systematically evaluated in placebo-controlled trials. Therefore, the physician who elects to use fluoxetine capsules, USP for extended periods, should periodically re-evaluate the long-term usefulness of the drug for the individual patient [see Dosage and Administration (2.2 )]. 1.3 Bulimia Nervosa Fluoxetine capsules, USP are indicated for the acute and maintenance treatment of binge-eating and vomiting behaviors in adult patients with moderate to severe Bulimia Nervosa [see Clinical Studies (14.3) ]. The physician who elects to use fluoxetine capsules, USP for extended periods should periodically re-evaluate the long-term usefulness of the drug for the individual patient [see Dosage and Administration (2.3 )] . 1.4 Panic Disorder Fluoxetine capsules, USP are indicated for the acute treatment of Panic Disorder, with or without agoraphobia, in adult patients [see Clinical Studies (14.4) ] . The effectiveness of fluoxetine capsules, USP in long-term use, i.e., for more than 12 weeks, has not been established in placebo-controlled trials. Therefore, the physician who elects to use fluoxetine capsules, USP for extended periods, should periodically re-evaluate the long-term usefulness of the drug for the individual patient [see Dosage and Administration (2.4) ]. 1.5 Fluoxetine Capsules, USP and Olanzapine in Combination: Depressive Episodes Associated with Bipolar I Disorder When using fluoxetine capsules, USP and olanzapine in combination, also refer to the Clinical Studies section of the package insert for Symbyax ® . Fluoxetine capsules, USP and olanzapine in combination are indicated for the acute treatment of depressive episodes associated with Bipolar I Disorder. Fluoxetine capsules, USP monotherapy is not indicated for the treatment of depressive episodes associated with Bipolar I Disorder.

Dosage

DOSAGE AND ADMINISTRATION Indication Adult Pediatric MDD ( 2.1 ) 20 mg/day in am (initial dose) 10 to 20 mg/day (initial dose) OCD ( 2.2 ) 20 mg/day in am (initial dose) 10 mg/day (initial dose) Bulimia Nervosa ( 2.3 ) 60 mg/day in am Panic Disorder ( 2.4 ) 10 mg/day (initial dose) Depressive Episodes Associated with Bipolar I Disorder ( 2.5 ) Oral in combination with olanzapine: 5 mg of oral olanzapine and 20 mg of fluoxetine once daily (initial dose) Oral in combination with olanzapine: 2.5 mg of oral olanzapine and 20 mg of fluoxetine once daily (initial dose) A lower or less frequent dosage should be used in patients with hepatic impairment, the elderly, and for patients with concurrent disease or on multiple concomitant medications ( 2.7 ) Fluoxetine capsules and olanzapine in combination: Dosage adjustments should be made with the individual components according to efficacy and tolerability ( 2.5 ) Fluoxetine monotherapy is not indicated for the treatment of Depressive Episodes associated with Bipolar I Disorder ( 2.5 ) Safety of the coadministration of doses above 18 mg olanzapine with 75 mg fluoxetine has not been evaluated in adults. ( 2.5 ) Safety of the coadministration of doses above 12 mg olanzapine with 50 mg fluoxetine has not been evaluated in children and adolescents ages 10 to 17 ( 2.5 ) 2.1 Major Depressive Disorder Initial Treatment Adult — Initiate fluoxetine 20 mg/day orally in the morning. Consider a dose increase after several weeks if insufficient clinical improvement is observed. Administer doses above 20 mg/day once daily in the morning or twice daily (i.e., morning and noon). The maximum fluoxetine dose should not exceed 80 mg/day. In controlled trials used to support the efficacy of fluoxetine, patients were administered morning doses ranging from 20 to 80 mg/day. Studies comparing fluoxetine 20, 40, and 60 mg/day to placebo indicate that 20 mg/day is sufficient to obtain a satisfactory response in Major Depressive Disorder in most cases [see Clinical Studies (14.1) ] . Pediatric (children and adolescents) — Initiate Fluoxetine 10 or 20 mg/day. After 1 week at 10 mg/day, increase the dose to 20 mg/day. However, due to higher plasma levels in lower weight children, the starting and target dose in this group may be 10 mg/day. Consider a dose increase to 20 mg/day after several weeks if insufficient clinical improvement is observed. In the short-term (8 to 9 week) controlled clinical trials of fluoxetine supporting its effectiveness in the treatment of Major Depressive Disorder, patients were administered fluoxetine doses of 10 to 20 mg/day [see Clinical Studies (14.1) ] . All patients — As with other drugs effective in the treatment of Major Depressive Disorder, the full effect may be delayed until 4 weeks of treatment or longer. Periodically reassess to determine the need for maintenance treatment. Switching Patients to a Tricyclic Antidepressant (TCA) — Dosage of a TCA may need to be reduced, and plasma TCA concentrations may need to be monitored temporarily when fluoxetine is coadministered or has been recently discontinued [see Warnings and Precautions (5.2) and Drug Interactions (7.7) ] . 2.2 Obsessive Compulsive Disorder Initial Treatment Adult — Initiate fluoxetine 20 mg/day, orally in the morning. Consider a dose increase after several weeks if insufficient clinical improvement is observed. The full therapeutic effect may be delayed until 5 weeks of treatment or longer. Administer doses above 20 mg/day once daily in the morning or twice daily (i.e., morning and noon). A dose range of 20 to 60 mg/day is recommended; however, doses of up to 80 mg/day have been well tolerated in open studies of OCD. The maximum fluoxetine dose should not exceed 80 mg/day. In the controlled clinical trials of fluoxetine supporting its effectiveness in the treatment of OCD, patients were administered fixed daily doses of 20, 40, or 60 mg of fluoxetine or placebo [see Clinical Studies (14.2) ] . In one of these studies, no dose-response relationship for effectiveness was demonstrated. Pediatric (children and adolescents) — In adolescents and higher weight children, initiate treatment with a dose of 10 mg/day. After 2 weeks, increase the dose to 20 mg/day. Consider additional dose increases after several more weeks if insufficient clinical improvement is observed. A dose range of 20 to 60 mg/day is recommended. In lower weight children, initiate treatment with a dose of 10 mg/day. Consider additional dose increases after several more weeks if insufficient clinical improvement is observed. A dose range of 20 to 30 mg/day is recommended. Experience with daily doses greater than 20 mg is very minimal, and there is no experience with doses greater than 60 mg. In the controlled clinical trial of fluoxetine supporting its effectiveness in the treatment of OCD, patients were administered fluoxetine doses in the range of 10 to 60 mg/day [see Clinical Studies (14.2) ] . Periodically reassess to determine the need for treatment. 2.3 Bulimia Nervosa Initial Treatment — Administer fluoxetine 60 mg/day in the morning. For some patients it may be advisable to titrate up to this target dose over several days. Fluoxetine doses above 60 mg/day have not been systematically studied in patients with bulimia. In the controlled clinical trials of fluoxetine supporting its effectiveness in the treatment of Bulimia Nervosa, patients were administered fixed daily fluoxetine doses of 20 or 60 mg, or placebo [see Clinical Studies (14.3) ] . Only the 60 mg dose was statistically significantly superior to placebo in reducing the frequency of binge-eating and vomiting. Periodically reassess to determine the need for maintenance treatment. 2.4 Panic Disorder Initial Treatment — Initiate treatment with fluoxetine 10 mg/day. After one week, increase the dose to 20 mg/day. Consider a dose increase after several weeks if no clinical improvement is observed. Fluoxetine doses above 60 mg/day have not been systematically evaluated in patients with Panic Disorder. In the controlled clinical trials of fluoxetine supporting its effectiveness in the treatment of Panic Disorder, patients were administered fluoxetine doses in the range of 10 to 60 mg/day [see Clinical Studies (14.4) ] . The most frequently administered dose in the 2 flexible-dose clinical trials was 20 mg/day. Periodically reassess to determine the need for continued treatment. 2.5 Fluoxetine and Olanzapine in Combination: Depressive Episodes Associated with Bipolar I Disorder When using fluoxetine and olanzapine in combination, also refer to the Clinical Studies section of the package insert for Symbyax. Adult — Administer fluoxetine in combination with oral olanzapine once daily in the evening, without regard to meals, generally beginning with 5 mg of oral olanzapine and 20 mg of fluoxetine. Make dosage adjustments, if indicated, according to efficacy and tolerability within dose ranges of fluoxetine 20 to 50 mg and oral olanzapine 5 to 12.5 mg. Antidepressant efficacy was demonstrated with olanzapine and fluoxetine in combination with a dose range of olanzapine 6 to 12 mg and fluoxetine 25 to 50 mg. Safety of co-administration of doses above 18 mg olanzapine with 75 mg fluoxetine has not been evaluated in clinical studies. Periodically re-examine the need for continued pharmacotherapy. Children and adolescents (10-17 years of age) — Administer olanzapine and fluoxetine combination once daily in the evening, generally beginning with 2.5 mg of olanzapine and 20 mg of fluoxetine. Make dosage adjustments, if indicated, according to efficacy and tolerability. Safety of co-administration of doses above 12 mg of olanzapine with 50 mg of fluoxetine has not been evaluated in pediatric clinical studies. Periodically re-examine the need for continued pharmacotherapy. Safety and efficacy of fluoxetine in combination with olanzapine was determined in clinical trials supporting approval of Symbyax (fixed-dose combination of

Warnings

WARNINGS AND PRECAUTIONS When using fluoxetine and olanzapine in combination, also refer to the Warnings and Precautions section of the package insert for Symbyax. Suicidal thoughts and Behaviors in Children, Adolescents, and Young Adults: Monitor for clinical worsening and suicidal thinking and behavior ( 5.1 ) Serotonin Syndrome: Serotonin syndrome has been reported with SSRIs and SNRIs, including fluoxetine , both when taken alone, but especially when co-administered with other serotonergic agents (including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, tryptophan, buspirone, amphetamines, and St. John's Wort). If such symptoms occur, discontinue fluoxetine and initiate supportive treatment. If concomitant use of fluoxetine with other serotonergic drugs is clinically warranted, patients should be made aware of a potential increased risk for serotonin syndrome, particularly during treatment initiation and dose increases. ( 5.2 ) Serotonin Syndrome: Serotonin syndrome has been reported with SSRIs and SNRIs, including fluoxetine , both when taken alone, but especially when co-administered with other serotonergic agents (including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, tryptophan, buspirone, amphetamines, and St. John's Wort). If such symptoms occur, discontinue fluoxetine and initiate supportive treatment. If concomitant use of fluoxetine with other serotonergic drugs is clinically warranted, patients should be made aware of a potential increased risk for serotonin syndrome, particularly during treatment initiation and dose increases. ( 5.2 ) Allergic Reactions and Rash: Discontinue upon appearance of rash or allergic phenomena ( 5.3 ) Activation of Mania/Hypomania: Screen for Bipolar Disorder and monitor for mania/hypomania ( 5.4 ) Seizures: Use cautiously in patients with a history of seizures or with conditions that potentially lower the seizure threshold ( 5.5 ) Altered Appetite and Weight: Significant weight loss has occurred ( 5.6 ) Abnormal Bleeding: May increase the risk of bleeding. Use with NSAIDs, aspirin, warfarin, or other drugs that affect coagulation may potentiate the risk of gastrointestinal or other bleeding ( 5.7 ) Angle-Closure Glaucoma: Angle-closure glaucoma has occurred in patients with untreated anatomically narrow angles treated with antidepressants. ( 5.8 ) Hyponatremia: Has been reported with fluoxetine in association with syndrome of inappropriate antidiuretic hormone (SIADH). Consider discontinuing if symptomatic hyponatremia occurs ( 5.9 ) Anxiety and Insomnia: May occur ( 5.10 ) QT Prolongation: QT prolongation and ventricular arrhythmia including Torsades de Pointes have been reported with fluoxetine use. Use with caution in conditions that predispose to arrhythmias or increased fluoxetine exposure. Use cautiously in patients with risk factors for QT prolongation ( 4.2 , 5.11 ) Potential for Cognitive and Motor Impairment: Has potential to impair judgment, thinking, and motor skills. Use caution when operating machinery ( 5.13 ) Long Half-Life: Changes in dose will not be fully reflected in plasma for several weeks ( 5.14 ) Fluoxetine and Olanzapine in Combination: When using Fluoxetine and olanzapine in combination, also refer to the Warnings and Precautions section of the package insert for Symbyax ( 5.16 ) 5.1 Suicidal Thoughts and Behaviors in Children, Adolescents, and Young Adults Patients with Major Depressive Disorder (MDD), both adult and pediatric, may experience worsening of their depression and/or the emergence of suicidal ideation and behavior (suicidality) or unusual changes in behavior, whether or not they are taking antidepressant medications, and this risk may persist until significant remission occurs. Suicide is a known risk of depression and certain other psychiatric disorders, and these disorders themselves are the strongest predictors of suicide. There has been a long-standing concern, however, that antidepressants may have a role in inducing worsening of depression and the emergence of suicidality in certain patients during the early phases of treatment. Pooled analyses of short-term placebo-controlled trials of antidepressant drugs (SSRIs and others) showed that these drugs increase the risk of suicidal thinking and behavior (suicidality) in children, adolescents, and young adults (ages 18 to 24) with Major Depressive Disorder (MDD) and other psychiatric disorders. Short-term studies did not show an increase in the risk of suicidality with antidepressants compared to placebo in adults beyond age 24; there was a reduction with antidepressants compared to placebo in adults aged 65 and older. The pooled analyses of placebo-controlled trials in children and adolescents with MDD, Obsessive Compulsive Disorder (OCD), or other psychiatric disorders included a total of 24 short-term trials of 9 antidepressant drugs in over 4400 patients. The pooled analyses of placebo-controlled trials in adults with MDD or other psychiatric disorders included a total of 295 short-term trials (median duration of 2 months) of 11 antidepressant drugs in over 77,000 patients. There was considerable variation in risk of suicidality among drugs, but a tendency toward an increase in the younger patients for almost all drugs studied. There were differences in absolute risk of suicidality across the different indications, with the highest incidence in MDD. The risk differences (drug versus placebo), however, were relatively stable within age strata and across indications. These risk differences (drug-placebo difference in the number of cases of suicidality per 1000 patients treated) are provided in Table 2. Table 2: Suicidality per 1000 Patients Treated Age Range Drug-Placebo Difference in Number of Cases of Suicidality per 1000 Patients Treated Increases Compared to Placebo <18 14 additional cases 18-24 5 additional cases Decreases Compared to Placebo 25-64 1 fewer case ≥65 6 fewer cases No suicides occurred in any of the pediatric trials. There were suicides in the adult trials, but the number was not sufficient to reach any conclusion about drug effect on suicide. It is unknown whether the suicidality risk extends to longer-term use, i.e., beyond several months. However, there is substantial evidence from placebo-controlled maintenance trials in adults with depression that the use of antidepressants can delay the recurrence of depression. All patients being treated with antidepressants for any indication should be monitored appropriately and observed closely for clinical worsening, suicidality, and unusual changes in behavior, especially during the initial few months of a course of drug therapy, or at times of dose changes, either increases or decreases. The following symptoms, anxiety, agitation, panic attacks, insomnia, irritability, hostility, aggressiveness, impulsivity, akathisia (psychomotor restlessness), hypomania, and mania, have been reported in adult and pediatric patients being treated with antidepressants for Major Depressive Disorder as well as for other indications, both psychiatric and nonpsychiatric. Although a causal link between the emergence of such symptoms and either the worsening of depression and/or the emergence of suicidal impulses has not been established, there is concern that such symptoms may represent precursors to emerging suicidality. Consideration should be given to changing the therapeutic regimen, including possibly discontinuing the medication, in patients whose depression is persistently worse, or who are experiencing emergent suicidality or symptoms that might be precursors to worsening depression or suicidality, especially if these symptoms are severe, abrupt in onset, or were not part of the patient’s presenting symptoms. If the decision has been made to discontinue treatment, medication should be tapered, as rapidly as is feasible, but with recognition that abrupt discontinuation can be associated with certain symptoms [see Warnings an

Contraindications

4. CONTRAINDICATIONS When using fluoxetine and olanzapine in combination, also refer to the Contraindications section of the package insert for olanzapine and fluoxetine hydrochloride capsules . Serotonin Syndrome and MAOIs: Do not use MAOIs intended to treat psychiatric disorders with fluoxetine or within 5 weeks of stopping treatment with fluoxetine. Do not use fluoxetine within 14 days of stopping an MAOI intended to treat psychiatric disorders. In addition, do not start fluoxetine in a patient who is being treated with linezolid or intravenous methylene blue (4.1) Pimozide: Do not use. Risk of QT prolongation and drug interaction (4.2, 5.11,7.7, 7.8) Thioridazine: Do not use. Risk of QT interval prolongation and elevated thioridazine plasma levels. Do not use thioridazine within 5 weeks of discontinuing fluoxetine Do not use thioridazine within 5 weeks of discontinuing fluoxetine (4.2, 5.11,7.7, 7.8). When using fluoxetine and olanzapine in combination, also refer to the Contraindications section of the package insert for olanzapine and fluoxetine hydrochloride capsules (4) 4.1 Monoamine Oxidase Inhibitors (MAOIs) The use of MAOIs intended to treat psychiatric disorders with fluoxetine or within 5 weeks of stopping treatment with fluoxetine is contraindicated because of an increased risk of serotonin syndrome. The use of fluoxetine within 14 days of stopping an MAOI intended to treat psychiatric disorders is also contraindicated [see Dosage and Administration (2.9) and Warnings and Precautions (5.2)]. Starting fluoxetine in a patient who is being treated with MAOIs such as linezolid or intravenous methylene blue is also contraindicated because of an increased risk of serotonin syndrome [see Dosage and Administration (2.10) and Warnings and Precautions (5.2)]. 4.2 Other Contraindications The use of fluoxetine is contraindicated with the following: • Pimozide [see Warnings and Precautions (5.11) and Drug Interactions (7.7, 7.8)] • Thioridazine [see Warnings and Precautions (5.11) and Drug Interactions (7.7, 7.8)] Pimozide and thioridazine prolong the QT interval. Fluoxetine can increase the levels of pimozide and thioridazine through inhibition of CYP2D6. Fluoxetine can also prolong the QT interval.

Mechanism of action

Mechanism of Action Although the exact mechanism of fluoxetine is unknown, it is presumed to be linked to its inhibition of CNS neuronal uptake of serotonin. 12.2 Pharmacodynamics Studies at clinically relevant doses in man have demonstrated that fluoxetine blocks the uptake of serotonin into human platelets. Studies in animals also suggest that fluoxetine is a much more potent uptake inhibitor of serotonin than of norepinephrine. Antagonism of muscarinic, histaminergic, and α1-adrenergic receptors has been hypothesized to be associated with various anticholinergic, sedative, and cardiovascular effects of classical tricyclic antidepressant (TCA) drugs. Fluoxetine binds to these and other membrane receptors from brain tissue much less potently in vitro than do the tricyclic drugs. 12.3 Pharmacokinetics Systemic Bioavailability — In man, following a single oral 40 mg dose, peak plasma concentrations of fluoxetine from 15 to 55 ng/mL are observed after 6 to 8 hours. The capsule and oral solution dosage forms of fluoxetine are bioequivalent. Food does not appear to affect the systemic bioavailability of fluoxetine, although it may delay its absorption by 1 to 2 hours, which is probably not clinically significant. Thus, fluoxetine may be administered with or without food. Protein Binding — Over the concentration range from 200 to 1000 ng/mL, approximately 94.5% of fluoxetine is bound in vitro to human serum proteins, including albumin and α1-glycoprotein. The interaction between fluoxetine and other highly protein-bound drugs has not been fully evaluated, but may be important. Enantiomers — Fluoxetine is a racemic mixture (50/50) of R-fluoxetine and S-fluoxetine enantiomers. In animal models, both enantiomers are specific and potent serotonin uptake inhibitors with essentially equivalent pharmacologic activity. The S-fluoxetine enantiomer is eliminated more slowly and is the predominant enantiomer present in plasma at steady state. Metabolism — Fluoxetine is extensively metabolized in the liver to norfluoxetine and a number of other unidentified metabolites. The only identified active metabolite, norfluoxetine, is formed by demethylation of fluoxetine. In animal models, S-norfluoxetine is a potent and selective inhibitor of serotonin uptake and has activity essentially equivalent to R- or S-fluoxetine. R-norfluoxetine is significantly less potent than the parent drug in the inhibition of serotonin uptake. The primary route of elimination appears to be hepatic metabolism to inactive metabolites excreted by the kidney. Variability in Metabolism — A subset (about 7%) of the population has reduced activity of the drug metabolizing enzyme cytochrome P450 2D6 (CYP2D6). Such individuals are referred to as “poor metabolizers” of drugs such as debrisoquin, dextromethorphan, and the TCAs. In a study involving labeled and unlabeled enantiomers administered as a racemate, these individuals metabolized S-fluoxetine at a slower rate and thus achieved higher concentrations of S-fluoxetine. Consequently, concentrations of S-norfluoxetine at steady state were lower. The metabolism of R-fluoxetine in these poor metabolizers appears normal. When compared with normal metabolizers, the total sum at steady state of the plasma concentrations of the 4 active enantiomers was not significantly greater among poor metabolizers. Thus, the net pharmacodynamic activities were essentially the same. Alternative, nonsaturable pathways (non-2D6) also contribute to the metabolism of fluoxetine. This explains how fluoxetine achieves a steady-state concentration rather than increasing without limit. Because fluoxetine’s metabolism, like that of a number of other compounds including TCAs and other selective serotonin reuptake inhibitors (SSRIs), involves the CYP2D6 system, concomitant therapy with drugs also metabolized by this enzyme system (such as the TCAs) may lead to drug interactions [see DRUG INTERACTIONS (7.7)]. Accumulation and Slow Elimination — The relatively slow elimination of fluoxetine (elimination half-life of 1 to 3 days after acute administration and 4 to 6 days after chronic administration) and its active metabolite, norfluoxetine (elimination half-life of 4 to 16 days after acute and chronic administration), leads to significant accumulation of these active species in chronic use and delayed attainment of steady state, even when a fixed dose is used [see WARNINGS AND PRECAUTIONS (5.14)]. After 30 days of dosing at 40 mg/day, plasma concentrations of fluoxetine in the range of 91 to 302 ng/mL and norfluoxetine in the range of 72 to 258 ng/mL have been observed. Plasma concentrations of fluoxetine were higher than those predicted by single-dose studies, because fluoxetine’s metabolism is not proportional to dose. Norfluoxetine, however, appears to have linear pharmacokinetics. Its mean terminal half-life after a single dose was 8.6 days and after multiple dosing was 9.3 days. Steady-state levels after prolonged dosing are similar to levels seen at 4 to 5 weeks. The long elimination half-lives of fluoxetine and norfluoxetine assure that, even when dosing is stopped, active drug substance will persist in the body for weeks (primarily depending on individual patient characteristics, previous dosing regimen, and length of previous therapy at discontinuation). This is of potential consequence when drug discontinuation is required or when drugs are prescribed that might interact with fluoxetine and norfluoxetine following the discontinuation of fluoxetine. 12.4 Specific Populations Liver Disease — As might be predicted from its primary site of metabolism, liver impairment can affect the elimination of fluoxetine. The elimination half-life of fluoxetine was prolonged in a study of cirrhotic patients, with a mean of 7.6 days compared with the range of 2 to 3 days seen in subjects without liver disease; norfluoxetine elimination was also delayed, with a mean duration of 12 days for cirrhotic patients compared with the range of 7 to 9 days in normal subjects. This suggests that the use of fluoxetine in patients with liver disease must be approached with caution. If fluoxetine is administered to patients with liver disease, a lower or less frequent dose should be used [see DOSAGE AND ADMINISTRATION (2.7), USE IN SPECIFIC POPULATIONS (8.6)]. Renal Disease — In depressed patients on dialysis (N=12), fluoxetine administered as 20 mg once daily for 2 months produced steady-state fluoxetine and norfluoxetine plasma concentrations comparable with those seen in patients with normal renal function. While the possibility exists that renally excreted metabolites of fluoxetine may accumulate to higher levels in patients with severe renal dysfunction, use of a lower or less frequent dose is not routinely necessary in renally impaired patients. Geriatric Pharmacokinetics — The disposition of single doses of fluoxetine in healthy elderly subjects (>65 years of age) did not differ significantly from that in younger normal subjects. However, given the long half-life and nonlinear disposition of the drug, a single-dose study is not adequate to rule out the possibility of altered pharmacokinetics in the elderly, particularly if they have systemic illness or are receiving multiple drugs for concomitant diseases. The effects of age upon the metabolism of fluoxetine have been investigated in 260 elderly but otherwise healthy depressed patients (≥60 years of age) who received 20 mg fluoxetine for 6 weeks. Combined fluoxetine plus norfluoxetine plasma concentrations were 209.3 ± 85.7 ng/mL at the end of 6 weeks. No unusual age-associated pattern of adverse reactions was observed in those elderly patients. Pediatric Pharmacokinetics (children and adolescents) — Fluoxetine pharmacokinetics were evaluated in 21 pediatric patients (10 children ages 6 to <13, 11 adolescents ages 13 to <18) diagnosed with Major Depressive Disorder or Obsessive Compulsive Disorder (OCD). Fluoxetine 20 mg/day was administered for u

Indicated ICD-10 codes

Source: RxNorm + openFDA + RxClass + FAERS · 2026

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