Drug Facts
Composition & Profile
Identifiers & Packaging
16 HOW SUPPLIED/STORAGE AND HANDLING 16.1 How Supplied Tetrabenazine tablets are available in the following strengths and packages: Tetrabenazine tablets 12.5 mg are formulated as light yellow to yellow, round shaped, flat, beveled edge tablets, debossed with “T” 12.5 on one side and plain on other side. Bottles of 112: NDC 70436-101-09 Tetrabenazine tablets 25 mg are formulated as light yellow to yellow, round shaped, flat, beveled edge tablets, debossed “T 25” on one side and functional scoreline on other side. Bottles of 112: NDC 70436-102-09 16.2 Storage Store at 25º C (77º F); excursions permitted to 15° to 30ºC (59° to 86º F) [see USP Controlled Room Temperature].; PACKAGE/LABEL PRINCIPAL DISPLAY PANEL 70436-101-09 70436-101-09; PACKAGE/LABEL PRINCIPAL DISPLAY PANEL 70436-102-09 70436-102-09
- 16 HOW SUPPLIED/STORAGE AND HANDLING 16.1 How Supplied Tetrabenazine tablets are available in the following strengths and packages: Tetrabenazine tablets 12.5 mg are formulated as light yellow to yellow, round shaped, flat, beveled edge tablets, debossed with “T” 12.5 on one side and plain on other side. Bottles of 112: NDC 70436-101-09 Tetrabenazine tablets 25 mg are formulated as light yellow to yellow, round shaped, flat, beveled edge tablets, debossed “T 25” on one side and functional scoreline on other side. Bottles of 112: NDC 70436-102-09 16.2 Storage Store at 25º C (77º F); excursions permitted to 15° to 30ºC (59° to 86º F) [see USP Controlled Room Temperature].
- PACKAGE/LABEL PRINCIPAL DISPLAY PANEL 70436-101-09 70436-101-09
- PACKAGE/LABEL PRINCIPAL DISPLAY PANEL 70436-102-09 70436-102-09
Overview
Tetrabenazine tablets contains tetrabenazine is a monoamine depletor for oral administration. The molecular weight of tetrabenazine is 317.42; the pKa is 6.51. Tetrabenazine is a hexahydro-dimethoxy‑benzoquinolizine derivative and has the following chemical name: cis rac –1,3,4,6,7,11b‑ hexahydro-9,10-dimethoxy-3-(2-methylpropyl)-2H-benzo[a]quinolizin-2-one. The empirical formula C 19 H 27 NO 3 is represented by the following structural formula: Tetrabenazine is a white to pale yellow powder that is soluble in chloroform and sparingly soluble in methanol. Each tetrabenazine tablet contains either 12.5 or 25 mg of tetrabenazine as the active ingredient. Tetrabenazine tablets contain tetrabenazine as the active ingredient and the following inactive ingredients: lactose monohydrate, pregelatinized starch, ferric oxide yellow, talc and magnesium stearate. Tetrabenazine tablets are supplied as a light yellow to yellow, functionally scored tablet containing 25 mg of tetrabenazine or as a light yellow to yellow, non-scored tablet containing 12.5 mg of tetrabenazine. tetrabenazine-str-01.jpg
Indications & Usage
Tetrabenazine tablets are indicated for the treatment of chorea associated with Huntington’s disease. Tetrabenazine tablets are a vesicular monoamine transporter 2 (VMAT) inhibitor indicated for the treatment of chorea associated with Huntington’s disease. (1)
Dosage & Administration
• Individualization of dose with careful weekly titration is required. The 1 st week’s starting dose is 12.5 mg daily; 2nd week, 25 mg (12.5 mg twice daily); then slowly titrate at weekly intervals by 12.5 mg to a tolerated dose that reduces chorea. (2.1 , 2.2) • Doses of 37.5 mg and up to 50 mg per day should be administered in three divided doses per day with a maximum recommended single dose not to exceed 25 mg. (2.2) • Patients requiring doses above 50 mg per day should be genotyped for the drug metabolizing enzyme CYP2D6 to determine if the patient is a poor metabolizer (PM) or an extensive metabolizer (EM). (2.2 , 5.3) • Maximum daily dose in PMs: 50 mg with a maximum single dose of 25 mg (2.2) • Maximum daily dose in EMs and intermediate metabolizers (IMs): 100 mg with a maximum single dose of 37.5 mg (2.2) • If serious adverse reactions occur, titration should be stopped and the dose should be reduced. If the adverse reaction(s) do not resolve, consider withdrawal of tetrabenazine. (2.2) 2.1 General Dosing Considerations The chronic daily dose of tetrabenazine tablets used to treat chorea associated with Huntington’s disease (HD) is determined individually for each patient. When first prescribed, tetrabenazine tablets therapy should be titrated slowly over several weeks to identify a dose of tetrabenazine that reduces chorea and is tolerated. Tetrabenazine tablets can be administered without regard to food [see Clinical Pharmacology (12.3) ] . 2.2 Individualization of Dose The dose of tetrabenazine tablets should be individualized. Dosing Recommendations Up to 50 mg per day The starting dose should be 12.5 mg per day given once in the morning. After 1 week, the dose should be increased to 25 mg per day given as 12.5 mg twice a day. Tetrabenazine tablets should be titrated up slowly at weekly intervals by 12.5 mg daily, to allow the identification of a tolerated dose that reduces chorea. If a dose of 37.5 to 50 mg per day is needed, it should be given in a three times a day regimen. The maximum recommended single dose is 25 mg. If adverse reactions such as akathisia, restlessness, parkinsonism, depression, insomnia, anxiety or sedation occur, titration should be stopped and the dose should be reduced. If the adverse reaction does not resolve, consideration should be given to withdrawing tetrabenazine treatment or initiating other specific treatment (e.g., antidepressants) [see Adverse Reactions (6.1) ] . Dosing Recommendations Above 50 mg per day Patients who require doses of tetrabenazine greater than 50 mg per day should be first tested and genotyped to determine if they are poor metabolizers (PMs) or extensive metabolizers (EMs) by their ability to express the drug metabolizing enzyme, CYP2D6. The dose of tetrabenazine tablets should then be individualized accordingly to their status as PMs or EMs [see Warnings and Precautions (5.3) , Use in Specific Populations (8.7) , Clinical Pharmacology (12.3) ] . Extensive and Intermediate CYP2D6 Metabolizers Genotyped patients who are identified as extensive (EMs) or intermediate metabolizers (IMs) of CYP2D6, who need doses of tetrabenazine tablets above 50 mg per day, should be titrated up slowly at weekly intervals by 12.5 mg daily, to allow the identification of a tolerated dose that reduces chorea. Doses above 50 mg per day should be given in a three times a day regimen. The maximum recommended daily dose is 100 mg and the maximum recommended single dose is 37.5 mg. If adverse reactions such as akathisia, parkinsonism, depression, insomnia, anxiety or sedation occur, titration should be stopped and the dose should be reduced. If the adverse reaction does not resolve, consideration should be given to withdrawing tetrabenazine tablets treatment or initiating other specific treatment (e.g., antidepressants) [see Warnings and Precautions (5.3) , Use in Specific Populations (8.7) , Clinical Pharmacology (12.3) ] . Poor CYP2D6 Metabolizers In PMs, the initial dose and titration is similar to EMs except that the recommended maximum single dose is 25 mg, and the recommended daily dose should not exceed a maximum of 50 mg [see Use in Specific Populations (8.7) , Clinical Pharmacology (12.3) ] . 2.3 Dosage Adjustment with CYP2D6 Inhibitors Strong CYP2D6 Inhibitors Medications that are strong CYP2D6 inhibitors such as quinidine or antidepressants (e.g., fluoxetine, paroxetine) significantly increase the exposure to α-HTBZ and β-HTBZ; therefore, the total dose of tetrabenazine tablets should not exceed a maximum of 50 mg and the maximum single dose should not exceed 25 mg [see Warnings and Precautions (5.3) , Drug Interactions (7.1) , Use in Specific Populations (8.7) , Clinical Pharmacology (12.3) ] . 2.4 Discontinuation of Treatment Treatment with tetrabenazine tablets can be discontinued without tapering. Re-emergence of chorea may occur within 12 to 18 hours after the last dose of tetrabenazine tablets [see Drug Abuse and Dependence (9.2) ] . 2.5 Resumption of Treatment Following treatment interruption of greater than five (5) days, tetrabenazine tablets therapy should be re-titrated when resumed. For short-term treatment interruption of less than five (5) days, treatment can be resumed at the previous maintenance dose without titration.
Warnings & Precautions
• Periodically reevaluate the benefit and potential for adverse effects such as worsening mood, cognition, rigidity, and functional capacity. (5.2) • Do not exceed 50 mg per day and the maximum single dose should not exceed 25 mg if administered in conjunction with a strong CYP2D6 inhibitor (e.g., fluoxetine, paroxetine). (5.3 , 7.1) • Neuroleptic Malignant Syndrome (NMS): Discontinue if this occurs. (5.4 , 7.6) • Restlessness, agitation, akathisia and parkinsonism: Reduce dose or discontinue if occurs. (5.5 , 5.6) • Sedation/Somnolence: May impair patient’s ability to drive or operate complex machinery (5.7) • QTc prolongation: Not recommended in combination with other drugs that prolong QTc (5.8) 5.1 Depression and Suicidality Patients with Huntington’s disease are at increased risk for depression, suicidal ideation or behaviors (suicidality). Tetrabenazine increases the risk for suicidality in patients with HD. In a 12-week, double-blind, placebo-controlled study in patients with chorea associated with Huntington’s disease, 10 of 54 patients (19%) treated with tetrabenazine tablets were reported to have an adverse event of depression or worsening depression compared to none of the 30 placebo-treated patients. In two open-label studies (in one study, 29 patients received tetrabenazine tablets for up to 48 weeks; in the second study, 75 patients received tetrabenazine tablets for up to 80 weeks), the rate of depression/worsening depression was 35%. In all of the HD chorea studies of tetrabenazine (n=187), one patient committed suicide, one attempted suicide, and six had suicidal ideation. When considering the use of tetrabenazine tablets, the risk of suicidality should be balanced against the need for treatment of chorea. All patients treated with tetrabenazine tablets should be observed for new or worsening depression or suicidality. If depression or suicidality does not resolve, consider discontinuing treatment with tetrabenazine tablets. Patients, their caregivers, and families should be informed of the risks of depression, worsening depression, and suicidality associated with tetrabenazine tablets, and should be instructed to report behaviors of concern promptly to the treating physician. Patients with HD who express suicidal ideation should be evaluated immediately. 5.2 Clinical Worsening and Adverse Effects Huntington’s disease is a progressive disorder characterized by changes in mood, cognition, chorea, rigidity, and functional capacity over time. In a 12-week controlled trial, tetrabenazine tablets was also shown to cause slight worsening in mood, cognition, rigidity, and functional capacity. Whether these effects persist, resolve, or worsen with continued treatment is unknown. Prescribers should periodically re-evaluate the need for tetrabenazine tablets in their patients by assessing the effect on chorea and possible adverse effects, including depression and suicidality, cognitive decline, parkinsonism, dysphagia, sedation/somnolence, akathisia, restlessness, and disability. It may be difficult to distinguish between adverse reactions and progression of the underlying disease; decreasing the dose or stopping the drug may help the clinician distinguish between the two possibilities. In some patients, underlying chorea itself may improve over time, decreasing the need for tetrabenazine tablets. 5.3 Laboratory Tests Before prescribing a daily dose of tetrabenazine tablets that is greater than 50 mg per day, patients should be genotyped to determine if they express the drug metabolizing enzyme, CYP2D6. CYP2D6 testing is necessary to determine whether patients are poor metabolizers (PMs), extensive (EMs) or intermediate metabolizers (IMs) of tetrabenazine tablets. Patients who are PMs of tetrabenazine tablets will have substantially higher levels of the primary drug metabolites (about 3-fold for α-HTBZ and 9-fold for β-HTBZ) than patients who are EMs. The dosage should be adjusted according to a patient’s CYP2D6 metabolizer status. In patients who are identified as CYP2D6 PMs, the maximum recommended total daily dose is 50 mg and the maximum recommended single dose is 25 mg [see Dosage and Administration (2.2) , Use in Specific Populations (8.7) , Clinical Pharmacology (12.3) ] . 5.4 Neuroleptic Malignant Syndrome (NMS) A potentially fatal symptom complex sometimes referred to as Neuroleptic Malignant Syndrome (NMS) has been reported in association with tetrabenazine tablets and other drugs that reduce dopaminergic transmission [see Drug Interactions (7.6) ] . Clinical manifestations of NMS are hyperpyrexia, muscle rigidity, altered mental status, and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, and cardiac dysrhythmia). Additional signs may include elevated creatinine phosphokinase, myoglobinuria, rhabdomyolysis, and acute renal failure. The diagnosis of NMS can be complicated; other serious medical illness (e.g., pneumonia, systemic infection), and untreated or inadequately treated extrapyramidal disorders can present with similar signs and symptoms. Other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, drug fever, and primary central nervous system pathology. The management of NMS should include (1) immediate discontinuation of tetrabenazine tablets; (2) intensive symptomatic treatment and medical monitoring; and (3) treatment of any concomitant serious medical problems for which specific treatments are available. There is no general agreement about specific pharmacological treatment regimens for NMS. Recurrence of NMS has been reported with resumption of drug therapy. If treatment with tetrabenazine tablets is needed after recovery from NMS, patients should be monitored for signs of recurrence. 5.5 Akathisia, Restlessness, and Agitation Tetrabenazine tablets may increase the risk of akathisia, restlessness, and agitation. In a 12-week, double-blind, placebo-controlled study in patients with chorea associated with HD, akathisia was observed in 10 (19%) of tetrabenazine tablets-treated patients and 0% of placebo-treated patients. In an 80-week, open-label study, akathisia was observed in 20% of tetrabenazine tablets-treated patients. Patients receiving tetrabenazine tablets should be monitored for the presence of akathisia. Patients receiving tetrabenazine tablets should also be monitored for signs and symptoms of restlessness and agitation, as these may be indicators of developing akathisia. If a patient develops akathisia, the tetrabenazine tablets dose should be reduced; however, some patients may require discontinuation of therapy. 5.6 Parkinsonism Tetrabenazine tablets can cause parkinsonism. In a 12-week, double-blind, placebo-controlled study in patients with chorea associated with HD, symptoms suggestive of parkinsonism (i.e., bradykinesia, hypertonia and rigidity) were observed in 15% of tetrabenazine tablets-treated patients compared to 0% of placebo-treated patients. In 48-week and 80-week, open-label studies, symptoms suggestive of parkinsonism were observed in 10% and 3% of tetrabenazine tablets-treated patients, respectively. Because rigidity can develop as part of the underlying disease process in Huntington’s disease, it may be difficult to distinguish between this drug-induced adverse reaction and progression of the underlying disease process. Drug-induced parkinsonism has the potential to cause more functional disability than untreated chorea for some patients with Huntington’s disease. If a patient develops parkinsonism during treatment with tetrabenazine tablets, dose reduction should be considered; in some patients, discontinuation of therapy may be necessary. 5.7 Sedation and Somnolence Sedation is the most common dose-limiting adverse reaction of tetrabenazine tablets. In a 12-week, double-blind, placebo-controlled trial in patients with chorea associated with HD, sedation/somnolence occurred in 17/54 (31%) of tetrabenazine tablets-treated patients and in 1 (3%) of placebo-treated patient. Sedation was the reason upward titration of tetrabenazine tablets was stopped and/or the dose of tetrabenazine tablets was decreased in 15/54 (28%) patients. In all but one case, decreasing the dose of tetrabenazine tablets resulted in decreased sedation. In 48-week and 80-week, open-label studies, sedation/somnolence occurred in 17% and 57% of tetrabenazine-treated patients, respectively. In some patients, sedation occurred at doses that were lower than recommended doses. Patients should not perform activities requiring mental alertness to maintain the safety of themselves or others, such as operating a motor vehicle or operating hazardous machinery, until they are on a maintenance dose of tetrabenazine and know how the drug affects them. 5.8 QTc Prolongation Tetrabenazine tablets causes a small increase (about 8 msec) in the corrected QT (QTc) interval. QT prolongation can lead to development of torsade de pointes-type ventricular tachycardia with the risk increasing as the degree of prolongation increases [see Clinical Pharmacology (12.2) ] . The use of tetrabenazine tablets should be avoided in combination with other drugs that are known to prolong QTc, including antipsychotic medications (e.g., chlorpromazine, haloperidol, thioridazine, ziprasidone), antibiotics (e.g., moxifloxacin), Class 1A (e.g., quinidine, procainamide) and Class III (e.g., amiodarone, sotalol) antiarrhythmic medications or any other medications known to prolong the QTc interval [see Drug Interactions (7.5) ] . Tetrabenazine tablets should also be avoided in patients with congenital long QT syndrome and in patients with a history of cardiac arrhythmias. Certain circumstances may increase the risk of the occurrence of torsade de pointes and/or sudden death in association with the use of drugs that prolong the QTc interval, including (1) bradycardia; (2) hypokalemia or hypomagnesemia; (3) concomitant use of other drugs that prolong the QTc interval; and (4) presence of congenital prolongation of the QT interval [see Clinical Pharmacology (12.2) ] . 5.9 Hypotension and Orthostatic Hypotension Tetrabenazine tablets induced postural dizziness in healthy volunteers receiving single doses of 25 or 50 mg. One subject had syncope, and one subject with postural dizziness had documented orthostasis. Dizziness occurred in 4% of tetrabenazine tablets-treated patients (vs. none on placebo) in the 12-week, controlled trial; however, blood pressure was not measured during these events. Monitoring of vital signs on standing should be considered in patients who are vulnerable to hypotension. 5.10 Hyperprolactinemia Tetrabenazine tablets elevates serum prolactin concentrations in humans. Following administration of 25 mg to healthy volunteers, peak plasma prolactin levels increased 4- to 5-fold. Tissue culture experiments indicate that approximately one third of human breast cancers are prolactin‑ dependent in vitro , a factor of potential importance if tetrabenazine tablets is being considered for a patient with previously detected breast cancer. Although amenorrhea, galactorrhea, gynecomastia, and impotence can be caused by elevated serum prolactin concentrations, the clinical significance of elevated serum prolactin concentrations for most patients is unknown. Chronic increase in serum prolactin levels (although not evaluated in the tetrabenazine tablets development program) has been associated with low levels of estrogen and increased risk of osteoporosis. If there is a clinical suspicion of symptomatic hyperprolactinemia, appropriate laboratory testing should be done and consideration should be given to discontinuation of tetrabenazine tablets. 5.11 Binding to Melanin-Containing Tissues Since tetrabenazine or its metabolites bind to melanin-containing tissues, it could accumulate in these tissues over time. This raises the possibility that tetrabenazine tablets may cause toxicity in these tissues after extended use. Neither ophthalmologic nor microscopic examination of the eye has been conducted in the chronic toxicity studies in a pigmented species, such as dogs. Ophthalmologic monitoring in humans was inadequate to exclude the possibility of injury occurring after long-term exposure. The clinical relevance of tetrabenazine’s binding to melanin-containing tissues is unknown. Although there are no specific recommendations for periodic ophthalmologic monitoring, prescribers should be aware of the possibility of long-term ophthalmologic effects [see Clinical Pharmacology (12.2) ] .
Boxed Warning
DEPRESSION AND SUICIDALITY Tetrabenazine can increase the risk of depression and suicidal thoughts and behavior (suicidality) in patients with Huntington’s disease. Anyone considering the use of tetrabenazine tablets must balance the risks of depression and suicidality with the clinical need for control of chorea. Close observation of patients for the emergence or worsening of depression, suicidality, or unusual changes in behavior should accompany therapy. Patients, their caregivers, and families should be informed of the risk of depression and suicidality and should be instructed to report behaviors of concern promptly to the treating physician. Particular caution should be exercised in treating patients with a history of depression or prior suicide attempts or ideation, which are increased in frequency in Huntington’s disease. Tetrabenazine tablets are contraindicated in patients who are actively suicidal, and in patients with untreated or inadequately treated depression [see Contraindications (4) , Warnings and Precautions (5.1) ] . WARNING: DEPRESSION AND SUICIDALITY See full prescribing information for complete boxed warning. • Increases the risk of depression and suicidal thoughts and behavior (suicidality) in patients with Huntington’s disease (5.1) • Balance risks of depression and suicidality with the clinical need for control of chorea when considering the use of tetrabenazine (5.2) • Monitor patients for the emergence or worsening of depression, suicidality, or unusual changes in behavior (5.1) • Inform patients, caregivers and families of the risk of depression and suicidality and instruct to report behaviors of concern promptly to the treating physician (5.1) • Exercise caution when treating patients with a history of depression or prior suicide attempts or ideation (5.1) • Tetrabenazine is contraindicated in patients who are actively suicidal, and in patients with untreated or inadequately treated depression (4 , 5.1)
Contraindications
Tetrabenazine tablets are contraindicated in patients: • Who are actively suicidal, or in patients with untreated or inadequately treated depression [see Warnings and Precautions (5.1) ] . • With hepatic impairment [see Use in Specific Populations (8.6) , Clinical Pharmacology (12.3) ] . • Taking monoamine oxidase inhibitors (MAOIs). Tetrabenazine tablets should not be used in combination with an MAOI, or within a minimum of 14 days of discontinuing therapy with an MAOI [see Drug Interactions (7.3) ] . • Taking reserpine. At least 20 days should elapse after stopping reserpine before starting tetrabenazine tablets [see Drug Interactions (7.2) ] . • Taking deutetrabenazine or valbenazine [see Drug Interactions (7.7) ]. • Actively suicidal, or who have depression which is untreated or undertreated (4 , 5.1) • Hepatic impairment (4 , 8.6 , 12.3) • Taking monoamine oxidase inhibitors (MAOIs) or reserpine (4 , 7.2 , 7.3) • Taking deutetrabenazine or valbenazine (4 , 7.7)
Adverse Reactions
The following serious adverse reactions are described below and elsewhere in the labeling: • Depression and Suicidality [see Warnings and Precautions (5.1) ] • Neuroleptic Malignant Syndrome (NMS) [see Warnings and Precautions (5.4) ] • Akathisia, Restlessness, and Agitation [see Warnings and Precautions (5.5) ] • Parkinsonism [see Warnings and Precautions (5.6) ] • Sedation and Somnolence [see Warnings and Precautions (5.7) ] • QTc Prolongation [see Warnings and Precautions (5.8) ] • Hypotension and Orthostatic Hypotension [see Warnings and Precautions (5.9) ] • Hyperprolactinemia [see Warnings and Precautions (5.10) ] • Binding to Melanin-Containing Tissues [see Warnings and Precautions (5.11) ] Most common adverse reactions (greater than 10% and at least 5% greater than placebo) were: sedation/somnolence, fatigue, insomnia, depression, akathisia, anxiety/anxiety aggravated, nausea. (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Slate Run Pharmaceuticals, LLC at 1-888-341-9214 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. During its development, tetrabenazine tablets was administered to 773 unique subjects and patients. The conditions and duration of exposure to tetrabenazine tablets varied greatly, and included single-dose and multiple-dose clinical pharmacology studies in healthy volunteers (n=259) and open-label (n=529) and double-blind studies (n=84) in patients. In a randomized, 12-week, placebo-controlled clinical trial of HD patients, adverse reactions were more common in the tetrabenazine group than in the placebo group. Forty-nine of 54 (91%) patients who received tetrabenazine tablets experienced one or more adverse reactions at any time during the study. The most common adverse reactions (over 10%, and at least 5% greater than placebo) were sedation/somnolence, fatigue, insomnia, depression, akathisia, anxiety/anxiety aggravated, and nausea. Adverse Reactions Occurring in ≥4% of Patients The number and percentage of the most common adverse reactions that occurred at any time during the study in ≥4% of tetrabenazine tablets-treated patients, and with a greater frequency than in placebo-treated patients, are presented in Table 1. Table 1: Adverse Reactions in a 12-Week, Double-Blind, Placebo-Controlled Trial in Patients with Huntington's Disease Adverse Reaction Tetrabenazine Tablets N=54 % Placebo N=30 % Sedation/somnolence 31 3 Insomnia 22 0 Fatigue 22 13 Depression 19 0 Akathisia 19 0 Anxiety/anxiety aggravated 15 3 Fall 15 13 Nausea 13 7 Upper respiratory tract infection 11 7 Irritability 9 3 Balance difficulty 9 0 Parkinsonism/bradykinesia 9 0 Vomiting 6 3 Laceration (head) 6 0 Ecchymosis 6 0 Decreased appetite 4 0 Obsessive reaction 4 0 Dizziness 4 0 Dysarthria 4 0 Unsteady gait 4 0 Headache 4 3 Shortness of breath 4 0 Bronchitis 4 0 Dysuria 4 0 Dose escalation was discontinued or dosage of study drug was reduced because of one or more adverse reactions in 28 of 54 (52%) patients randomized to tetrabenazine tablets. These adverse reactions consisted of sedation (15), akathisia (7), parkinsonism (4), depression (3), anxiety (2), fatigue (1) and diarrhea (1). Some patients had more than one AR and are, therefore, counted more than once. Adverse Reactions Due to Extrapyramidal Symptoms Table 2 describes the incidence of events considered to be extrapyramidal adverse reactions which occurred at a greater frequency in tetrabenazine tablets-treated patients compared to placebo- treated patients. Table 2: Adverse Reactions Due to Extrapyramidal Symptoms in a 12-Week, Double- Blind, Placebo-Controlled Trial in Patients with Huntington’s Disease Tetrabenazine Tablets n = 54 % Placebo n = 30 % Akathisia* 19 0 Extrapyramidal event† 15 0 Any extrapyramidal event 33 0 *Patients with the following adverse event preferred terms were counted in this category: akathisia, hyperkinesia, restlessness. † Patients with the following adverse event preferred terms were counted in this category: bradykinesia, parkinsonism, extrapyramidal disorder, hypertonia. Patients may have had events in more than one category. Dysphagia Dysphagia is a component of HD. However, drugs that reduce dopaminergic transmission have been associated with esophageal dysmotility and dysphagia. Dysphagia may be associated with aspiration pneumonia. In a 12-week, double-blind, placebo-controlled study in patients with chorea associated with HD, dysphagia was observed in 4% of tetrabenazine tablets-treated patients and 3% of placebo-treated patients. In 48-week and 80-week, open-label studies, dysphagia was observed in 10% and 8% of tetrabenazine tablets-treated patients, respectively. Some of the cases of dysphagia were associated with aspiration pneumonia. Whether these events were related to treatment is unknown. 6.2 Postmarketing Experience The following adverse reactions have been identified during post-approval use of tetrabenazine tablets. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Nervous system disorders: tremor Psychiatric disorders: confusion, worsening aggression Respiratory, thoracic and mediastinal disorders: pneumonia Skin and subcutaneous tissue disorders: hyperhidrosis, skin rash
Drug Interactions
7.1 Strong CYP2D6 Inhibitors In vitro studies indicate that α-HTBZ and β-HTBZ are substrates for CYP2D6. Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine, quinidine) markedly increase exposure to these metabolites. A reduction in tetrabenazine dose may be necessary when adding a strong CYP2D6 inhibitor (e.g., fluoxetine, paroxetine, quinidine) in patients maintained on a stable dose of tetrabenazine tablets. The daily dose of tetrabenazine tablets should not exceed 50 mg per day and the maximum single dose of tetrabenazine tablets should not exceed 25 mg in patients taking strong CYP2D6 inhibitors [see Dosage and Administration (2.3) , Warnings and Precautions (5.3) , Use in Specific Populations (8.7) , Clinical Pharmacology (12.3) ] . 7.2 Reserpine Reserpine binds irreversibly to VMAT2, and the duration of its effect is several days. Prescribers should wait for chorea to re-emerge before administering tetrabenazine tablets to avoid overdosage and major depletion of serotonin and norepinephrine in the CNS. At least 20 days should elapse after stopping reserpine before starting tetrabenazine tablets. Tetrabenazine tablets and reserpine should not be used concomitantly [see Contraindications (4) ] . 7.3 Monoamine Oxidase Inhibitors (MAOIs) Tetrabenazine tablets are contraindicated in patients taking MAOIs. Tetrabenazine tablets should not be used in combination with an MAOI, or within a minimum of 14 days of discontinuing therapy with an MAOI [see Contraindications (4) ] . 7.4 Alcohol or Other Sedation Drugs Concomitant use of alcohol or other sedating drugs may have additive effects and worsen sedation and somnolence [see Warnings and Precautions (5.7) ]. 7.5 Drugs That Cause QTc Prolongation Tetrabenazine tablets causes a small prolongation of QTc (about 8 msec), concomitant use with other drugs that are known to cause QTc prolongation should be avoided, these including antipsychotic medications (e.g., chlorpromazine, haloperidol, thioridazine, ziprasidone), antibiotics (e.g., moxifloxacin), Class 1A (e.g., quinidine, procainamide) and Class III (e.g., amiodarone, sotalol) antiarrhythmic medications or any other medications known to prolong the QTc interval. Tetrabenazine should be avoided in patients with congenital long QT syndrome and in patients with a history of cardiac arrhythmias. Certain conditions may increase the risk for torsade de pointes or sudden death such as (1) bradycardia; (2) hypokalemia or hypomagnesemia; (3) concomitant use of other drugs that prolong the QTc interval; and (4) presence of congenital prolongation of the QT interval [see Warnings and Precautions (5.8) , Clinical Pharmacology (12.2) ] . 7.6 Neuroleptic Drugs The risk for Parkinsonism, NMS, and akathisia may be increased by concomitant use of tetrabenazine tablets and dopamine antagonists or antipsychotics (e.g., chlorpromazine, haloperidol, olanzapine, risperidone, thioridazine, ziprasidone) [see Warnings and Precautions (5.4 , 5.5 , 5.6) ]. 7.7 Concomitant Deutetrabenazine or Valbenazine Tetrabenazine tablets are contraindicated in patients currently taking deutetrabenazine or valbenazine.
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