CLOZAPINE

Severe neutropenia: See Boxed Warning (5.1) Gastrointestinal Hypomotility with Severe Complications: Severe gastrointestinal adverse reactions have occurred with the use of clozapine tablets. If constipation is identified, close monitoring and prompt treatment is advised. ( 5.7 ) Eosinophilia: Assess for organ involvement (e.g., myocarditis, pancreatitis, hepatitis, colitis, nephritis). Discontinue if these occur. ( 5.8 ) QT Interval Prolongation: Can be fatal. Consider additional risk factors for prolonged QT interval (disorders and drugs). ( 5.9 ) Metabolic Changes: Atypical antipsychotic drugs have been associated with metabolic changes that may increase cardiovascular/cerebrovascular risk. These metabolic changes include: Hyperglycemia and Diabetes Mellitus: Monitor for symptoms of hyperglycemia including polydipsia, polyuria, polyphagia, and weakness. Monitor glucose regularly in patients with diabetes or at risk for diabetes. (5.10) Dyslipidemia: Undesirable alterations in lipids have occurred in patients treated with atypical antipsychotics. (5.10) Weight Gain: Significant weight gain has occurred. Monitor weight gain. (5.10) Neuroleptic Malignant Syndrome (NMS): Immediately discontinue and monitor closely. Assess for co-morbid conditions. (5.11) Hepatotoxicity: Can be fatal. Monitor for hepatotoxicity. Discontinue treatment if hepatitis or transaminase elevations combined with other symptoms occur (5.12) . Fever: Evaluate for infection and for neutropenia, NMS. (5.13) Pulmonary Embolism (PE): Consider PE if respiratory distress, chest pain, or deep-vein thrombosis occur. (5.14) Anticholinergic Toxicity: When possible, avoid use with other anticholinergic drugs and use with caution in patients with a current diagnosis or prior history of constipation, urinary retention, clinically significant prostatic hypertrophy, or other conditions in which anticholinergic effects can lead to significant adverse reactions. ( 5.15 , 7.1 ) Interference with Cognitive and Motor Performance: Advise caution when operating machinery, including automobiles. (5.16) 5.1 Severe Neutropenia Clozapine tablets has caused severe neutropenia (absolute neutrophil count (ANC) less than 500/μL) [see Adverse Reactions ( 6.1 , 6.2) ] and is associated with an increased risk of serious and potentially fatal infections. Severe neutropenia occurred in a small percentage of clozapine tablets-treated patients. The risk of severe neutropenia appears greatest during the first 18 weeks of clozapine tablets treatment. The mechanism by which clozapine tablets causes neutropenia is unknown. Neutropenia is not dose dependent. Consider a hematology consultation before initiating clozapine tablets treatment or during treatment. ANC Monitoring and Dosage Modifications Prior to initiating clozapine tablets treatment, obtain a baseline ANC. Clozapine tablets initiation is not recommended in patients with a baseline ANC less than 1500/μL. Throughout clozapine tablets treatment, regularly monitor ANC. Table 1 provides recommendations for dosage modifications (dosage interruption and treatment discontinuation), based on ANC levels, during clozapine tablets treatment and frequency of ANC monitoring [see Dosage and Administration (2.3) ]. ANC Monitoring and Dosage Modification in Patients with Benign Ethnic Neutropenia Patients with Benign Ethnic Neutropenia (BEN) (also known as Duffy-null associated neutrophil count) generally have lower baseline neutrophil counts but they are not at higher risk for developing infections, and they are not at increased risk for developing clozapine tablets-induced neutropenia. For patients with documented BEN, obtain at least two baseline ANC levels prior to clozapine tablets initiation. Clozapine tablets initiation is not recommended in patients with BEN with an ANC less than 1000/μL. There are different ANC dosage modification recommendations in clozapine tablets-treated patients with BEN due to their lower baseline ANC levels. Table 2 provides recommendations on dosage modifications (dosage interruption and treatment discontinuation), based on ANC monitoring, during clozapine tablets treatment in patients with BEN and recommended frequency of ANC testing [see Dosage and Administration (2.4) ]. Management of Clozapine Tablets-Treated Patients Who Develop a Fever For patients who develop a fever during clozapine tablets treatment: Interrupt clozapine tablets in those who develop a temperature of 101.3 °F (38.5 °C) or greater and obtain an ANC level. If the ANC is less than 1000/μL in patients without BEN, initiate appropriate workup and treatment for infection. Refer to Table 1 or Table 2 for dosage modifications based on ANC monitoring [see Dosage and Administration ( 2.3 , 2.4 )] . In patients with fever and a normal neutrophil count, see Warnings and Precautions (5.11) for neuroleptic malignant syndrome and Warnings and Precautions (5.13) for fever. Restarting Clozapine Tablets in Patients Who Recovered from Severe Neutropenia Generally, do not rechallenge patients with clozapine tablets in those who experienced severe neutropenia. However, for some patients who had resolution of their clozapine tablets-related severe neutropenia after stopping clozapine tablets, the risk of schizophrenia exacerbation from not restarting clozapine tablets treatment may be greater than the risk of neutropenia reoccurrence from restarting clozapine tablets (e.g., patients who have no treatment options other than clozapine tablets). Concomitant Use of clozapine tablets with Other Drugs Known to Cause Neutropenia If clozapine tablets are used concomitantly with another drug known to cause neutropenia, consider more frequently ANC monitoring than the recommendations provided in Table 1 and Table 2. 5.2 Orthostatic Hypotension, Bradycardia, and Syncope Hypotension, bradycardia, syncope, and cardiac arrest have occurred with clozapine treatment. The risk is highest during the initial titration period, particularly with rapid dose-escalation. These reactions can occur with the first dose, at doses as low as 12.5 mg. These reactions can be fatal. The syndrome is consistent with neurally mediated reflex bradycardia (NMRB). Treatment must begin at a maximum dose of 12.5 mg once daily or twice daily. The total daily dose can be increased in increments of 25 mg to 50 mg per day, if well-tolerated, to a target dose of 300 mg to 450 mg per day (administered in divided doses) by the end of 2 weeks. Subsequently, the dose can be increased weekly or twice weekly, in increments of up to 100 mg. The maximum dose is 900 mg per day. Use cautious titration and a divided dosage schedule to minimize the risk of serious cardiovascular reactions [see Dosage and Administration (2.2)]. Consider reducing the dose if hypotension occurs. When restarting clozapine tablets in patients who have had even a brief interruption in treatment with clozapine tablets, the dosage must be reduced. This is necessary to minimize the risk of hypotension, bradycardia, and syncope [see Dosage and Administration (2.6) ]. Use clozapine tablets cautiously in patients with cardiovascular disease (history of myocardial infarction or ischemia, heart failure, or conduction abnormalities), cerebrovascular disease, and conditions which would predispose patients to hypotension (e.g., concomitant use of antihypertensives, dehydration and hypovolemia). 5.3 Falls Clozapine tablets may cause somnolence, postural hypotension, motor and sensory instability, which may lead to falls and, consequently, fractures or other injuries. For patients with diseases, conditions, or medications that could exacerbate these effects, complete fall risk assessments when initiating antipsychotic treatment and recurrently for patients on long-term antipsychotic therapy. 5.4 Seizures Seizure has been estimated to occur in association with clozapine use at a cumulative incidence at one year of approximately 5%, based on the occurrence of one or more seizures in 61 of 1743 patients exposed to clozapine during its clinical testing prior to domestic marketing (i.e., a crude rate of 3.5%). The risk of seizure is dose-related. Initiate treatment with a low dose (12.5 mg), titrate slowly, and use divided dosing. Use caution when administering clozapine tablets to patients with a history of seizures or other predisposing risk factors for seizure (e.g., head trauma or other CNS pathology, use of medications that lower the seizure threshold, or alcohol abuse). Because of the substantial risk of seizure associated with clozapine tablets use, caution patients about engaging in any activity where sudden loss of consciousness could cause serious risk to themselves or others (e.g., driving an automobile, operating complex machinery, swimming, climbing). 5.5 Myocarditis, Pericarditis, Cardiomyopathy and Mitral Valve Incompetence Myocarditis, pericarditis, and cardiomyopathy have occurred with the use of clozapine. These reactions can be fatal. Discontinue clozapine and obtain a cardiac evaluation upon suspicion of myocarditis, pericarditis, or cardiomyopathy. Generally, patients with a history of clozapine-associated myocarditis, or cardiomyopathy should not be rechallenged with clozapine. However, if the benefit of clozapine tablets treatment is judged to outweigh the potential risks of recurrence, the clinician may consider rechallenge with clozapine tablets in consultation with a cardiologist. Myocarditis and pericarditis most frequently present within the first 2 months of clozapine treatment. Symptoms of cardiomyopathy generally occur later than clozapine-associated myocarditis or pericarditis and usually after 8 weeks of treatment. However, myocarditis, pericarditis, and cardiomyopathy can occur at any period during treatment with clozapine. In patients who are diagnosed with cardiomyopathy while taking clozapine tablets mitral valve incompetence has been reported. 5.6 Increased Mortality in Elderly Patients with Dementia-Related Psychosis Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death. Analyses of 17 placebo-controlled trials (modal duration of 10 weeks), largely in patients taking atypical antipsychotic drugs, revealed a risk of death in drug-treated patients of between 1.6 to 1.7 times the risk of death in placebo-treated patients. Over the course of a typical 10-week controlled trial, the rate of death in drug-treated patients was about 4.5%, compared to a rate of about 2.6% in the placebo group. Although the causes of death were varied, most of the deaths appeared to be either cardiovascular (e.g., heart failure, sudden death) or infectious (e.g., pneumonia) in nature. Observational studies suggest that, similar to atypical antipsychotic drugs, treatment with conventional antipsychotic drugs may increase mortality in this population. The extent to which the findings of increased mortality in observational studies may be attributed to the antipsychotic drug as opposed to some characteristic(s) of the patients is not clear. Clozapine tablets are not approved for the treatment of patients with dementia-related psychosis [see Boxed Warning ] . 5.7 Gastrointestinal Hypomotility with Severe Complications Severe gastrointestinal adverse reactions have occurred with the use of clozapine, primarily due to its potent anticholinergic effects and resulting gastrointestinal hypomotility. In post marketing experience, reported effects range from constipation to paralytic ileus. Increased frequency of constipation and delayed diagnosis and treatment increased the risk of severe complications of gastrointestinal hypomotility, which can result in fecal impaction, megacolon, and intestinal obstruction, ischemia, infarction, perforation, ulceration, or necrosis [see Adverse Reaction (6.2) ] . These reactions have resulted in hospitalization, surgery, and death. The risk of severe adverse reactions is further increased with anticholinergic medications (and other medications that decrease gastrointestinal peristalsis); therefore, concomitant use should be avoided when possible [see Warnings and Precautions (5.15) , Drug Interactions (7.1) ] . Prior to initiating clozapine, screen for constipation and treat as necessary. Subjective symptoms of constipation may not accurately reflect the degree of gastrointestinal hypomotility in clozapine tablets treated patients. Therefore, reassess bowel function frequently with careful attention to any changes in the frequency or character of bowel movements, as well as signs and symptoms of complications of hypomotility (e.g., nausea, vomiting, abdominal distension, abdominal pain). If constipation or gastrointestinal hypomotility are identified, monitor closely and treat promptly with appropriate laxatives, as necessary, to prevent severe complications. Consider prophylactic laxatives in high risk patients. 5.8 Eosinophilia Eosinophilia, defined as a blood eosinophil count of greater than 700/µL, has occurred with clozapine tablets treatment. In clinical trials, approximately 1% of patients developed eosinophilia. Clozapine-related eosinophilia usually occurs during the first month of treatment. In some patients, it has been associated with myocarditis, pancreatitis, hepatitis, colitis, and nephritis. Such organ involvement could be consistent with a drug reaction with eosinophilia and systemic symptoms syndrome (DRESS), also known as drug induced hypersensitivity syndrome (DIHS). If eosinophilia develops during clozapine tablets treatment, evaluate promptly for signs and symptoms of systemic reactions, such as rash or other allergic symptoms, myocarditis, or other organ-specific disease associated with eosinophilia. If clozapine-related systemic disease is suspected, discontinue clozapine tablets immediately. If a cause of eosinophilia unrelated to clozapine tablets are identified (e.g., asthma, allergies, collagen vascular disease, parasitic infections, and specific neoplasms), treat the underlying cause and continue clozapine. Clozapine-related eosinophilia has also occurred in the absence of organ involvement and can resolve without intervention. There are reports of successful rechallenge after discontinuation of clozapine without recurrence of eosinophilia. In the absence of organ involvement, continue clozapine tablets under careful monitoring. If the total eosinophil count continues to increase over several weeks in the absence of systemic disease, the decision to interrupt clozapine tablets therapy and rechallenge after the eosinophil count decreases should be based on the overall clinical assessment, in consultation with an internist or hematologist. 5.9 QT Interval Prolongation QT prolongation, Torsade de Pointes and other life-threatening ventricular arrhythmias, cardiac arrest, and sudden death have occurred with clozapine tablets treatment. When prescribing clozapine, consider the presence of additional risk factors for QT prolongation and serious cardiovascular reactions. Conditions that increase these risks include the following: history of QT prolongation, long QT syndrome, family history of long QT syndrome or sudden cardiac death, significant cardiac arrhythmia, recent myocardial infarction, uncompensated heart failure, treatment with other medications that cause QT prolongation, treatment with medications that inhibit the metabolism of clozapine, and electrolyte abnormalities. Prior to initiating treatment with clozapine, perform a careful physical examination, medical history, and concomitant medication history. Consider obtaining a baseline ECG and serum chemistry panel. Correct electrolyte abnormalities. Discontinue clozapine tablets if the QTc interval exceeds 500 msec. If patients experience symptoms consistent with Torsades de Pointes, or other arrhythmias (e.g., syncope, presyncope, dizziness, or palpitations), obtain a cardiac evaluation and discontinue clozapine. Use caution when administering concomitant medications that prolong the QT interval or inhibit the metabolism of clozapine. Drugs that cause QT prolongation include: specific antipsychotics (e.g., ziprasidone, iloperidone, chlorpromazine, thioridazine, mesoridazine, droperidol, pimozide), specific antibiotics (e.g., erythromycin, gatifloxacin, moxifloxacin, sparfloxacin), Class 1A antiarrhythmic medications (e.g., quinidine, procainamide) or Class III antiarrhythmics (e.g., amiodarone, sotalol), and others (e.g., pentamidine, levomethadyl acetate, methadone, halofantrine, mefloquine, dolasetron mesylate, probucol or tacrolimus). Clozapine is primarily metabolized by CYP isoenzymes 1A2, 2D6, and 3A4. Concomitant treatment with inhibitors of these enzymes can increase the concentration of clozapine tablets [see Drug Interactions (7.1) and Clinical Pharmacology (12.3) ] . Hypokalemia and hypomagnesemia increase the risk of QT prolongation. Hypokalemia can result from diuretic therapy, diarrhea, and other causes. Use caution when treating patients at risk for significant electrolyte disturbance, particularly hypokalemia. Obtain baseline measurements of serum potassium and magnesium levels, and periodically monitor electrolytes. Correct electrolyte abnormalities before initiating treatment with clozapine tablets. 5.10 Metabolic Changes Atypical antipsychotic drugs, including clozapine tablets have been associated with metabolic changes that can increase cardiovascular and cerebrovascular risk. These metabolic changes include hyperglycemia, dyslipidemia, and body weight gain. While atypical antipsychotic drugs may produce some metabolic changes, each drug in the class has its own specific risk profile. Hyperglycemia and Diabetes Mellitus Hyperglycemia, in some cases extreme and associated with ketoacidosis or hyperosmolar coma or death, has been reported in patients treated with atypical antipsychotics including clozapine. Assessment of the relationship between atypical antipsychotic use and glucose abnormalities is complicated by the possibility of an increased background risk of diabetes mellitus in patients with schizophrenia and the increasing incidence of diabetes mellitus in the general population. Given these confounders, the relationship between atypical antipsychotic use and hyperglycemia-related adverse reactions is not completely understood. However, epidemiological studies suggest an increased risk of treatment-emergent, hyperglycemia-related adverse reactions in patients treated with the atypical antipsychotics. Precise risk estimates for hyperglycemia-related adverse reactions in patients treated with atypical antipsychotics are not available. Patients with an established diagnosis of diabetes mellitus who are started on clozapine tablets should be monitored regularly for worsening of glucose control. Patients with risk factors for diabetes mellitus (e.g., obesity, family history of diabetes) who are starting treatment with atypical antipsychotics should undergo fasting blood glucose testing at the beginning of treatment and periodically during treatment. Any patient treated with atypical antipsychotics should be monitored for symptoms of hyperglycemia including polydipsia, polyuria, polyphagia, and weakness. Patients who develop symptoms of hyperglycemia during treatment with atypical antipsychotics should undergo fasting blood glucose testing. In some cases, hyperglycemia has resolved when the atypical antipsychotic was discontinued; however, some patients required continuation of antidiabetic treatment despite discontinuation of the suspect drug. In a pooled data analysis of 8 studies in adult subjects with schizophrenia, the mean changes in fasting glucose concentration in the clozapine and chlorpromazine groups were +11 mg/dL and +4 mg/dL respectively. A higher proportion of the clozapine group demonstrated categorical increases from baseline in fasting glucose concentrations, compared to the chlorpromazine group ( Table 4 ). The clozapine doses were 100 mg to 900 mg per day (mean modal dose: 512 mg per day). The maximum chlorpromazine dose was 1800 mg per day (mean modal dose: 1029 mg per day). The median duration of exposure was 42 days for clozapine and chlorpromazine. Table 4. Categorical Changes in Fasting Glucose Level in Studies in Adult Subjects with Schizophrenia Laboratory Parameter Category Change (at least once) from baseline Treatment Arm N n (%) Fasting Glucose Normal (<100 mg/dL) to High (≥126 mg/dL) Clozapine 198 53 (27) Chlorpromazine 135 14 (10) Borderline (100 to 125 mg/dL) to High (≥126 mg/dL) Clozapine 57 24 (42) Chlorpromazine 43 12 (28) Dyslipidemia Undesirable alterations in lipids have occurred in patients treated with atypical antipsychotics, including clozapine. Clinical monitoring, including baseline and periodic follow-up lipid evaluations in patients using clozapine, is recommended. In a pooled data analysis of 10 studies in adult subjects with schizophrenia, clozapine treatment was associated with increases in serum total cholesterol. No data were collected on LDL and HDL cholesterol. The mean increase in total cholesterol was 13 mg/dL in the clozapine group and 15 mg/dL in the chlorpromazine group. In a pooled data analysis of 2 studies in adult subjects with schizophrenia, clozapine treatment was associated with increases in fasting serum triglyceride. The mean increase in fasting triglyceride was 71 mg/dL (54%) in the clozapine group and 39 mg/dL (35%) in the chlorpromazine group ( Table 5 ). In addition, clozapine treatment was associated with categorical increases in serum total cholesterol and triglyceride, as illustrated in Table 6 . The proportion of patients with categorical increases in total cholesterol or fasting triglyceride increased with the duration of exposure. The median duration of clozapine and chlorpromazine exposure was 45 days and 38 days, respectively. The clozapine dose range was 100 mg to 900 mg daily; the maximum chlorpromazine dose was 1800 mg daily. Table 5. Mean Changes in Total Cholesterol and Triglyceride Concentration in Studies in Adult Subjects with Schizophrenia Treatment Arm Baseline total cholesterol concentration (mg/dL) Change from baseline mg/dL (%) Clozapine (N=334) 184 +13 (7) Chlorpromazine (N=185) 182 +15 (8) Baseline triglyceride concentration (mg/dL) Change from baseline mg/dL (%) Clozapine (N=6) 130 +71 (54) Chlorpromazine (N=7) 110 +39 (35) Table 6. Categorical Changes in Lipid Concentrations in Studies in Adult Subjects with Schizophrenia Laboratory Parameter Category Change (at least once) from baseline Treatment Arm N n (%) Total Cholesterol (random or fasting) Increase by ≥40 mg/dL Clozapine 334 111 (33) Chlorpromazine 185 46 (25) Normal (<200 mg/dL) to High (≥240 mg/dL) Clozapine 222 18 (8) Chlorpromazine 132 3 (2) Borderline (200 to 239 mg/dL) to High (≥240 mg/dL) Clozapine 79 30 (38) Chlorpromazine 34 14 (41) Triglycerides (fasting) Increase by ≥50 mg/dL Clozapine 6 3 (50) Chlorpromazine 7 3 (43) Normal (<150 mg/dL) to High (≥200 mg/dL) Clozapine 4 0 (0) Chlorpromazine 6 2 (33) Borderline (≥150 mg/dL and <200 mg/dL) to High (≥200 mg/dL) Clozapine 1 1 (100) Chlorpromazine 1 0 (0) Weight Gain Weight gain has occurred with the use of antipsychotics, including clozapine. Monitor weight during treatment with clozapine. Table 7 summarizes the data on weight gain by the duration of exposure pooled from 11 studies with clozapine and active comparators. The median duration of exposure was 609, 728, and 42 days, in the clozapine, olanzapine, and chlorpromazine group, respectively. Table 7. Mean Change in Body Weight (kg) by Duration of Exposure from Studies in Adult Subjects with Schizophrenia Metabolic parameter Exposure duration Clozapine (N=669) Olanzapine (N=442) Chlorpromazine (N=155) n Mean n Mean n Mean Weight change from baseline 2 weeks (Day 11 to 17) 6 +0.9 3 +0.7 2 -0.5 4 weeks (Day 21 to 35) 23 +0.7 8 +0.8 17 +0.6 8 weeks (Day 49 to 63) 12 +1.9 13 +1.8 16 +0.9 12 weeks (Day 70 to 98) 17 +2.8 5 +3.1 0 0 24 weeks (Day 154 to 182) 42 -0.6 12 +5.7 0 0 48 weeks (Day 322 to 350) 3 +3.7 3 +13.7 0 0 Table 8 summarizes pooled data from 11 studies in adult subjects with schizophrenia demonstrating weight gain ≥7% of body weight relative to baseline. The median duration of exposure was 609, 728, and 42 days, in the clozapine, olanzapine, and chlorpromazine group, respectively. Table 8. Proportion of Adult Subjects in Schizophrenia Studies with Weight Gain ≥7% Relative to Baseline Body Weight Weight change Clozapine Olanzapine Chlorpromazine N 669 442 155 ≥7% (inclusive) 236 (35%) 203 (46%) 13 (8%) 5.11 Neuroleptic Malignant Syndrome Antipsychotic drugs including clozapine can cause a potentially fatal symptom complex referred to as Neuroleptic Malignant Syndrome (NMS). Clinical manifestations of NMS include hyperpyrexia, muscle rigidity, altered mental status, and autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, and cardiac dysrhythmias). Associated findings can include elevated creatine phosphokinase (CPK), myoglobinuria, rhabdomyolysis, and acute renal failure. The diagnostic evaluation of patients with this syndrome is complicated. It is important to consider the presence of other serious medical conditions (e.g., severe neutropenia, infection, heat stroke, primary CNS pathology, central anticholinergic toxicity, extrapyramidal symptoms, and drug fever). The management of NMS should include (1) immediate discontinuation of antipsychotic drugs and other drugs not essential to concurrent therapy, (2) intensive symptomatic treatment and medical monitoring, and (3) treatment of comorbid medical conditions. There is no general agreement about specific pharmacological treatments for NMS. If a patient requires antipsychotic drug treatment after recovery from NMS, the potential reintroduction of drug therapy should be carefully considered. NMS can recur. Monitor closely if restarting treatment with antipsychotics. NMS has occurred with clozapine monotherapy and with concomitant CNS-active medications, including lithium. 5.12 Hepatotoxicity Severe, life threatening, and in some cases fatal hepatotoxicity including hepatic failure, hepatic necrosis, and hepatitis have been reported in post marketing studies in patients treated with clozapine [see Adverse Reactions (6.2)]. Monitor for the appearance of signs and symptoms of hepatotoxicity such as fatigue, malaise, anorexia, nausea, jaundice, bilirubinemia, coagulopathy, and hepatic encephalopathy. Perform serum tests for liver injury and consider permanently discontinuing treatment if hepatitis or transaminase elevations combined with other systemic symptoms are due to clozapine. 5.13 Fever During clozapine therapy, patients have experienced transient, clozapine-related fever. The peak incidence is within the first 3 weeks of treatment. While this fever is generally benign and self-limited, it may necessitate discontinuing treatment. The fever can be associated with an increase or decrease in WBC count. Carefully evaluate patients with fever to rule out severe neutropenia or infection. Consider the possibility of NMS [see Warnings and Precautions (5.11)]. 5.14 Pulmonary Embolism Pulmonary embolism and deep-vein thrombosis have occurred in patients treated with clozapine. Consider the possibility of pulmonary embolism in patients who present with deep-vein thrombosis, acute dyspnea, chest pain, or with other respiratory signs and symptoms. Whether pulmonary embolus and deep-vein thrombosis can be attributed to clozapine or some characteristic(s) of patients is not clear. 5.15 Anticholinergic Toxicity Clozapine tablets has potent anticholinergic effects. Treatment with clozapine tablets can result in CNS and peripheral anticholinergic toxicity, especially at higher dosages, or in overdose situations [see Overdosage (10)] . Use with caution in patients with a current diagnosis or prior history of constipation, urinary retention, clinically significant prostatic hypertrophy, or other conditions in which anticholinergic effects can lead to significant adverse reactions. When possible, avoid concomitant use, with other anticholinergic medications because the risk for anticholinergic toxicity or severe gastrointestinal adverse reactions is increased [see Warnings and Precautions (5.7), Drug Interactions (7.1) ] . 5.16 Interference with Cognitive and Motor Performance Clozapine tablets can cause sedation and impairment of cognitive and motor performance. Caution patients about operating hazardous machinery, including automobiles, until they are reasonably certain that clozapine tablets does not affect them adversely. These reactions may be dose-related. Consider reducing the dose if they occur. 5.17 Tardive Dyskinesia Tardive dyskinesia (TD) has occurred in patients treated with antipsychotic drugs, including clozapine. The syndrome consists of potentially irreversible, involuntary, dyskinetic movements. The risk of TD and the likelihood that it will become irreversible are believed to increase with greater durations of treatment and higher total cumulative doses. However, the syndrome can develop after relatively brief treatment periods at low doses. Prescribe clozapine tablets in a manner that is most likely to minimize the risk of developing TD. Use the lowest effective dose and the shortest duration necessary to control symptoms. Periodically assess the need for continued treatment. Consider discontinuing treatment if TD occurs. However, some patients may require treatment with clozapine tablets despite the presence of the syndrome. TD may remit partially or completely if treatment is discontinued. Antipsychotic treatment, itself, may suppress (or partially suppress) the signs and symptoms, and it has the potential to mask the underlying process. The effect of symptom suppression on the long-term course of TD is unknown. 5.18 Cerebrovascular Adverse Reactions In controlled trials, elderly patients with dementia-related psychosis treated with some atypical antipsychotics had an increased risk (compared to placebo) of cerebrovascular adverse reactions (e.g., stroke, transient ischemic attack), including fatalities. The mechanism for this increased risk is not known. An increased risk cannot be excluded for clozapine tablets or other antipsychotics or other patient populations. Clozapine tablets should be used with caution in patients with risk factors for cerebrovascular adverse reactions. 5.19 Recurrence of Psychosis and Cholinergic Rebound after Abrupt Discontinuation of Clozapine Tablets If abrupt discontinuation of clozapine tablets are necessary (because of severe neutropenia or another medical condition, for example) [see Dosage and Administration (2.5) , Warnings and Precautions (5.1) ] , monitor carefully for the recurrence of psychotic symptoms and adverse reactions related to cholinergic rebound, such as profuse sweating, headache, nausea, vomiting and diarrhea.