Tetrabenazine

Contraindications ( 4 ) 9/2017 Warnings and Precautions, Tardive Dyskinesia (5.12-removal) 9/2017

1 INDICATIONS AND 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 )

2 DOSAGE AND ADMINISTRATION Individualization of dose with careful weekly titration is required. The 1 st week’s starting dose is 12.5 mg daily; 2 nd 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 tablets. ( 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 tablets 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 one 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 mg 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 tablets 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 tablets 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 …

3 DOSAGE FORMS AND STRENGTHS Tetrabenazine tablets are available in the following strengths: Tetrabenazine tablets 12.5 mg are available for oral administration as white to off-white, round, flat face, bevelled edge, unscored tablets, engraved “T12.5” on one side, “APO” on the other side. Tetrabenazine tablets 25 mg are available for oral administration as yellow, round, flat face, bevelled edge tablets with functional scoring on one side, engraved “APO” over “T25” on the other side. Tablets: 12.5 mg non-scored and 25 mg with functional score ( 3 )

4 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 )

6 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 Oceanside Pharmaceuticals at 1-800-321-4576 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 were administered to 773 unique subjects and patients. The conditions and duration of exposure to tetrabenazine 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 tablets 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 Greater Than or Equal to 4% of Patients The number and percentage of the most common adverse reactions that occurred at any time during the study in greater than or equal to 4% of tetrabenazine tablet-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 tablet-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 …

7 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 tablets 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 Sedating 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 cause 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 tablets 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.

Drug Interactions CYP2D6 Inhibitors In vitro studies indicate that α-HTBZ and β-HTBZ are substrates for CYP2D6. The effect of CYP2D6 inhibition on the pharmacokinetics of tetrabenazine and its metabolites was studied in 25 healthy subjects following a single 50 mg dose of tetrabenazine given after 10 days of administration of the strong CYP2D6 inhibitor paroxetine 20 mg daily. There was an approximately 30% increase in C max and an approximately 3-fold increase in AUC for α-HTBZ in subjects given paroxetine prior to tetrabenazine compared to tetrabenazine given alone. For β-HTBZ, the C max and AUC were increased 2.4- and 9-fold, respectively, in subjects given paroxetine prior to tetrabenazine given alone. The elimination half-life of α-HTBZ and β-HTBZ was approximately 14 hours when tetrabenazine was given with …

8 USE IN SPECIFIC POPULATIONS Pregnancy: Based on animal data, may cause fetal harm. ( 8.1 ) 8.1 Pregnancy Risk Summary There are no adequate data on the developmental risk associated with the use of tetrabenazine in pregnant women. Administration of tetrabenazine to rats throughout pregnancy and lactation resulted in an increase in stillbirths and postnatal offspring mortality. Administration of a major human metabolite of tetrabenazine to rats during pregnancy or during pregnancy and lactation produced adverse effects on the developing fetus and offspring (increased mortality, decreased growth, and neurobehavioral and reproductive impairment). The adverse developmental effects of tetrabenazine and a major human metabolite of tetrabenazine in rats occurred at clinically relevant doses [see Data]. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown. Data Animal Data Tetrabenazine had no clear effects on embryofetal development when administered to pregnant rats throughout the period of organogenesis at oral doses up to 30 mg/kg/day (or 3 times the maximum recommended human dose [MRHD] of 100 mg/day on a mg/m 2 basis). Tetrabenazine had no effects on embryofetal development when administered to pregnant rabbits during the period of organogenesis at oral doses up to 60 mg/kg/day (or 12 times the MRHD on a mg/m 2 basis). When tetrabenazine (5 mg/kg/day, 15 mg/kg/day, and 30 mg/kg/day) was orally administered to pregnant rats from the beginning of organogenesis through the lactation period, an increase in stillbirths and offspring postnatal mortality was observed at 15 mg/kg/day and 30 mg/kg/day and delayed pup maturation was observed at all doses. A no-effect dose for pre-and postnatal developmental toxicity in rats was not identified. The lowest dose tested (5 mg/kg/day) was less than the MRHD on a mg/m 2 basis. Because rats dosed orally with tetrabenazine do not produce 9-desmethyl-β-DHTBZ, a major human metabolite of tetrabenazine, the metabolite was directly administered to pregnant and lactating rats. Oral administration of 9-desmethyl-β-DHTBZ (8 mg/kg/day, 15 mg/kg/day, and 40 mg/kg/day) throughout the period of organogenesis produced increases in embryofetal mortality at 15 mg/kg/day and 40 mg/kg/day and reductions in fetal body weights at 40 mg/kg/day, which was also maternally toxic. When 9-desmethyl-β-DHTBZ (8 mg/kg/day, 15 mg/kg/day, and 40 mg/kg/day) was orally administered to pregnant rats from the beginning of organogenesis through the lactation period, increases in gestation duration, stillbirths, and offspring postnatal mortality (40 mg/kg/day); decreases in pup weights (40 mg/kg/day); and neurobehavioral (increased activity, learning and memory deficits) and reproductive (decreased litter size) impairment (15 mg/kg/day and 40 mg/kg/day) were observed. Maternal toxicity was seen at the highest dose. The no-effect dose for developmental toxicity in rats (8 mg/kg/day) was associated with plasma exposures (AUC) of 9-desmethyl-β-DHTBZ in pregnant rats lower than that in humans at the MRHD. 8.2 Lactation Risk Summary There are no data on the presence of tetrabenazine or its metabolites in human milk, the effects on the breastfed infant, or the effects of the drug on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for tetrabenazine and any potential adverse effects on the breastfed infant from tetrabenazine or from the underlying maternal condition. 8.4 Pediatric Use Safety and effectiveness in pediatric patients have not been established. 8.5 Geriatric Use The pharmacokinetics of tetrabenazine and its primary metabolites have not been formally studied in geriatric subjects. 8.6 Hepatic Impairment Because the safety …

12.1 Mechanism of Action The precise mechanism by which tetrabenazine exerts its anti-chorea effects is unknown but is believed to be related to its effect as a reversible depletor of monoamines (such as dopamine, serotonin, norepinephrine, and histamine) from nerve terminals. Tetrabenazine reversibly inhibits the human vesicular monoamine transporter type 2 (VMAT2) (K i ≈ 100 nM), resulting in decreased uptake of monoamines into synaptic vesicles and depletion of monoamine stores. Human VMAT2 is also inhibited by dihydrotetrabenazine (HTBZ), a mixture of α-HTBZ and β-HTBZ. α-and β-HTBZ, major circulating metabolites in humans, exhibit high in vitro binding affinity to bovine VMAT2. Tetrabenazine exhibits weak in vitro binding affinity at the dopamine D2 receptor (K i = 2100 nM). i ≈ 100 nM), resulting in decreased uptake of monoamines into synaptic vesicles and depletion of monoamine stores. Human VMAT2 is also inhibited by dihydrotetrabenazine (HTBZ), a mixture of α-HTBZ and β-HTBZ. α- and β-HTBZ, major circulating metabolites in humans, exhibit high in vitro binding affinity to bovine VMAT2. Tetrabenazine exhibits weak in vitro binding affinity at the dopamine D2 receptor (K i = 2100 nM).

11 DESCRIPTION Tetrabenazine is a monoamine depletor for oral administration. The molecular weight of tetrabenazine is 317.43; the pKa is 6.51. Tetrabenazine is a hexahydro-dimethoxy-benzoquinolizine derivative and has the following chemical name: cis rac –1,3,4,6,7,11bhexahydro-9,10-dimethoxy-3-(2-methylpropyl)-2H-benzo[a]quinolizin-2-one. The molecular formula C 19 H 27 NO 3 is represented by the following structural formula: Tetrabenazine is off-white to pale yellow powder that is sparingly soluble in methanol and soluble in chloroform. 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, ferric oxide yellow, corn starch, pregelatinized starch, magnesium stearate and talc. The 12.5 mg tetrabenazine tablets are light yellow to yellow colored, round, flat faced beveled edge, non-scored tablets debossed with ‘T1’ on one side and plain on other side. The 25 mg tetrabenazine tablets are light yellow to yellow colored, round, flat faced beveled edge, functionally scored tablets debossed with ‘T’ on both side of scored line and plain on other side. structure

10 OVERDOSAGE Three episodes of overdose occurred in the open-label trials performed in support of registration. Eight cases of overdose with tetrabenazine tablets have been reported in the literature. The dose of tetrabenazine tablets in these patients ranged from 100 mg to 1 g. Adverse reactions associated with tetrabenazine tablets overdose include acute dystonia, oculogyric crisis, nausea and vomiting, sweating, sedation, hypotension, confusion, diarrhea, hallucinations, rubor, and tremor. Treatment should consist of those general measures employed in the management of overdosage with any CNS-active drug. General supportive and symptomatic measures are recommended. Cardiac rhythm and vital signs should be monitored. In managing overdosage, the possibility of multiple drug involvement should always be considered. The physician should consider contacting a poison control center on the treatment of any overdose.

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 available for oral administration as white to off-white, round, flat face, bevelled edge, unscored tablets, engraved "T12.5" on one side, "APO" on the other side. They are supplied as follows: Bottles of 112 NDC 51407-480-12 Tetrabenazine tablets 25 mg are available for oral administration as yellow, round, flat face, bevelled edge tablets with functional scoring on one side, engraved "APO" over "T25" on the other side. They are supplied as follows: Bottles of 112 NDC 51407-481-12 16.2 Storage Store at 20oC to 25oC (68oF to 77oF); excursions permitted from 15oC to 30oC (59oF to 86oF) [see USP Controlled Room Temperature].