1. Name Of The Medicinal Product
Denzapine 50 mg/ml Oral Suspension
As a consequence of a recent European regulatory initiative, the Denzapine Summary of Product Characteristics (SmPC) has been harmonised across Europe. The SmPC states that blood monitoring should be carried out in accordance with national-specific official recommendations. These are reproduced below.
The Denzapine Monitoring Service (DMS) was developed in order to manage the risk of agranulocytosis associated with clozapine. It is available 24 hours a day. When a monitoring service is not used, evidence suggests a mortality rate from agranulocytosis of 0.3%[1]. This is compared to a mortality rate when clozapine is used in conjunction with a Monitoring Service, of 0.01%[2].
The Denzapine Monitoring Service provides for the centralised monitoring of leucocyte and neutrophil counts which is a mandatory requirement for all patients in the UK and Ireland who are treated with Denzapine. The use of Denzapine is restricted to patients who are registered with the Denzapine Monitoring Service. In addition to registering their patients, prescribing physicians must register themselves and a nominated pharmacist with the Denzapine Monitoring Service. All Denzapine-treated patients must be under the supervision of an appropriate specialist and supply of Denzapine is restricted to hospital and retail pharmacies registered with the Denzapine Monitoring Service. Denzapine is not sold to, or distributed through wholesalers.
The patient's white cell count with a differential count must be monitored:
• At least weekly for the first 18 weeks of treatment
• At least at 2 week intervals between weeks 18 and 52
• After 1 year of treatment with stable blood counts (green range), patients may be monitored at least at 4 week intervals
• Monitoring must continue throughout treatment and for at least 4 weeks after discontinuation
If the blood result of a patient taking Denzapine is below the normal range (See Section 4.4), Genus will contact the physician and pharmacist registered to the patient on the Denzapine Monitoring Service to inform them.
The Denzapine Monitoring Service maintains a database which includes all patients who have developed abnormal leucocyte or neutrophil findings and who should not be re-exposed to Denzapine or any other brand of clozapine.
Prescribers and pharmacists should adhere to brand prescribing and dispensing of clozapine in order to prevent the disruption to effective monitoring that may be caused if patients switch brands.
Furthermore, in order to protect patient safety, at any one time patients should only be prescribed one brand of clozapine and only registered with the monitoring service connected to that brand.
For further information regarding Denzapine and the Denzapine Monitoring Service please call 0333 200 4141 (UK).
[1] De la Chapelle A, et al. Clozapine-induced agranulocytosis: a genetic and epidemiologic study. Hum Genet, 1977. 37: p. 183-194.
[2] Denzapine Monitoring Service, data on file.
DENZAPINE can cause agranulocytosis. Its use should be limited to patients:
• with schizophrenia who are non-responsive to or intolerant of antipsychotic drug treatment, or with psychosis in Parkinson's disease when other treatment strategies have failed (see point 4.1)
• who have initially normal leukocyte findings (white blood cell count of > 3500/mm3 (3.5 x 109 /L), and an absolute neutrophil count (ANC) of >2000/mm3 (2.0 x 109 /L)), and
• in whom regular white blood cell (WBC) counts and absolute neutrophil counts (ANC) can be performed as follows: weekly during the first 18 weeks of therapy, and at least every 4 weeks thereafter throughout treatment. Monitoring must continue throughout treatment and for 4 weeks after complete discontinuation of DENZAPINE.
Prescribing physicians should comply fully with the required safety measures. At each consultation, a patient receiving DENZAPINE should be reminded to contact the treating physician immediately if any kind of infection begins to develop. Particular attention should be paid to flu-like complaints such as fever or sore throat and to other evidence of infection, which may be indicative of neutropenia.
DENZAPINE must be dispensed under strict medical supervision in accordance with official recommendations.
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Myocarditis
Clozapine is associated with an increased risk of myocarditis which has, in rare cases, been fatal. The increased risk of myocarditis is greatest in the first 2 months of treatment. Fatal cases of cardiomyopathy have also been reported rarely.
Myocarditis or cardiomyopathy should be suspected in patients who experience persistent tachycardia at rest, especially in the first 2 months of treatment, and/or palpitations, arrhythmias, chest pain and other signs and symptoms of heart failure (e.g. unexplained fatigue, dyspnoea, tachypnoea) or symptoms that mimic myocardial infarction.
If myocarditis or cardiomyopathy are suspected, DENZAPINE treatment should be promptly stopped and the patient immediately referred to a cardiologist.
Patients who develop clozapine-induced myocarditis or cardiomyopathy should not be re-exposed to clozapine.
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2. Qualitative And Quantitative Composition
Each 1ml of oral suspension contains 50mg of Clozapine.
Excipients:
Each 1ml of oral suspension also contains 150mg sorbitol, 2mg sodium methyl parahydroxybenzoate and 0.2mg sodium propyl parahydroxybenzoate.
For full list of excipients, see section 6.1.
3. Pharmaceutical Form
Oral suspension
Free-flowing yellow suspension
4. Clinical Particulars
4.1 Therapeutic Indications
DENZAPINE is indicated in treatment-resistant schizophrenic patients and in schizophrenia patients who have severe, untreatable neurological adverse reactions to other antipsychotic agents, including atypical antipsychotics.
Treatment resistance is defined as a lack of satisfactory clinical improvement despite the use of adequate doses of at least two different antipsychotic agents, including an atypical antipsychotic agent, prescribed for adequate duration.
DENZAPINE is also indicated in psychotic disorders occurring during the course of Parkinson's disease, in cases where standard treatment has failed.
4.2 Posology And Method Of Administration
Method of Administration - Oral
When first dispensed or when there is visible settling of the suspension, Clozapine Suspension should be shaken well for 90 seconds before being dispensed or used. In all other instances the bottle should be shaken for 10 seconds before a dose is dispensed.
If dilution is required, the suspension may be mixed with water but not fruit juice or any other form of liquid.
The dosage must be adjusted individually. For each patient the lowest effective dose should be used.
Initiation of DENZAPINE treatment must be restricted to those patients with a WBC count over 3500/mm3 (3.5 x 109/L) and an absolute neutrophil count (ANC) greater than 2000/mm3 (2.0 x 109/L) within standardised normal limits.
Dose adjustment is indicated in patients who are also receiving medicinal products that have pharmacodynamic and pharmacokinetic interactions with DENZAPINE, such as benzodiazepines or selective serotonin re-uptake inhibitors (see section 4.5 Interaction with other medicinal products and other forms of interaction).
The following dosages are recommended:
Treatment-resistant schizophrenic patients
Starting therapy
12.5 mg (0.25 ml of suspension) once or twice on the first day, followed by 25 mg (0.5 ml of suspension) or 50mg (1.0 ml of suspension) on the second day. If well tolerated, the daily dose may then be increased slowly in increments of 25 to 50 mg (0.5 ml to 1.0 ml of suspension) in order to achieve a dose level of up to 300 mg/day within 2 to 3 weeks. Thereafter, if required, the daily dose may be further increased in increments of 50 to 100 mg (1.0 ml to 2.0 ml of suspension) at half-weekly or, preferably, weekly intervals.
Use in children
Not Recommended in Children.
Use in the elderly
Initiation of treatment is recommended at a particularly low dose (12.5 mg given once on the first day), with subsequent dose increments restricted to 25 mg/day.
Therapeutic dose range
In most patients, antipsychotic efficacy can be expected with 200 to 450 mg/day (4 ml to 9 ml/day) given in divided doses. The total daily dose may be divided unevenly, with the larger portion at bedtime. For maintenance dose, see below.
Maximum dose
To obtain full therapeutic benefit, a few patients may require larger doses, in which case judicious increments (i.e. not exceeding 100 mg or 2 ml) are permissible up to 900 mg/day (18 ml). The possibility of increased adverse reactions (in particular seizures) occurring at doses over 450 mg/day (9 ml/day) must be borne in mind.
Maintenance dose
After achieving maximum therapeutic benefit, many patients can be maintained effectively on lower doses. Careful downward titration is therefore recommended. Treatment should be maintained for at least 6 months. If the daily dose does not exceed 200 mg, once daily administration in the evening may be appropriate.
Ending therapy
In the event of planned termination of DENZAPINE therapy, a gradual reduction in dose over a 1- to 2-week period is recommended. If abrupt discontinuation is necessary (e.g. because of leucopoenia), the patient should be carefully observed for the recurrence of psychotic symptoms and symptoms related to cholinergic rebound, such as profuse sweating, headache, nausea, vomiting and diarrhoea.
Re-starting therapy
In patients in whom the interval since the last dose of DENZAPINE suspension exceeds 2 days, treatment should be re-initiated with 12.5 mg (0.25 ml) given once or twice on the first day. If this dose is well tolerated, it may be feasible to titrate the dose to the therapeutic level more quickly than is recommended for initial treatment. However, in any patient who has previously experienced respiratory or cardiac arrest with initial dosing (see section 4.4 Special warnings and precautions for use), but was then able to be successfully titrated to a therapeutic dose, re-titration should be carried out with extreme caution.
Switching from a previous antipsychotic therapy to DENZAPINE
It is generally recommended that DENZAPINE should not be used in combination with other antipsychotics, including depot preparations, which may have a myelosuppressive effect. When DENZAPINE therapy is to be initiated in a patient undergoing oral antipsychotic therapy, it is recommended that the other antipsychotic should first be discontinued by tapering the dosage downwards.
Psychotic disorders occurring during the course of Parkinson's disease, in cases where standard treatment has failed
The starting dose must not exceed 12.5 mg/day (0.25 ml) taken in the evening. Subsequent dose increases must be by 12.5 mg increments (0.25 ml), with a maximum of two increments a week up to a maximum of 50 mg (1 ml), a dose that cannot be reached until the end of the second week. The total daily amount should preferably be given as a single dose in the evening.
The mean effective dose is usually between 25 and 37.5 mg/day (0.5 and 0.75 ml/day). In the event that treatment for at least one week with a dose of 50 mg (1 ml) fails to provide a satisfactory therapeutic response, dosage may be cautiously increased by increments of 12.5 mg/week (0.25 ml/week).
The dose of 50 mg/day (1 ml/day) should only be exceeded in exceptional cases, and the maximum dose of 100 mg/day (2 ml/day) must never be exceeded.
Dose increases should be limited or deferred if orthostatic hypotension, excessive sedation or confusion occurs. Blood pressure should be monitored during the first weeks of treatment.
When there has been complete remission of psychotic symptoms for at least 2 weeks, an increase in anti-parkinsonian medication is possible if indicated on the basis of motor status. If this approach results in the recurrence of psychotic symptoms, DENZAPINE dosage may be increased by increments of 12.5 mg/week (0.25 ml/week) up to a maximum of 100 mg/day (2 ml/day), taken in one or two divided doses (see above).
Ending therapy: A gradual reduction in dose by steps of 12.5 mg (0.25 ml) over a period of at least one week (preferably two) is recommended.
Treatment must be discontinued immediately in the event of neutropenia or agranulocytosis as indicated in section 4.4 (Special warnings and precautions for use). In this situation, careful psychiatric monitoring of the patient is essential since symptoms may recur quickly.
4.3 Contraindications
• Hypersensitivity to the active substance or to any of the excipients.
• Patients with known or suspected hereditary problems of fructose intolerance should not take this oral suspension
• Patients unable to undergo regular blood tests.
• History of toxic or idiosyncratic granulocytopenia/agranulocytosis (with the exception of granulocytopenia/agranulocytosis from previous chemotherapy).
• History of DENZAPINE -induced agranulocytosis.
• Impaired bone marrow function.
• Uncontrolled epilepsy.
• Alcoholic and other toxic psychoses, drug intoxication, comatose conditions.
• Circulatory collapse and/or CNS depression of any cause.
• Severe renal or cardiac disorders (e.g. myocarditis).
• Active liver disease associated with nausea, anorexia or jaundice; progressive liver disease, hepatic failure.
• Paralytic ileus.
• DENZAPINE treatment must not be started concurrently with drugs known to have a substantial potential for causing agranulocytosis; concomitant use of depot antipsychotics is to be discouraged.
4.4 Special Warnings And Precautions For Use
Precautions
DENZAPINE can cause agranulocytosis. The incidence of agranulocytosis and the fatality rate in those developing agranulocytosis have decreased markedly since the institution of WBC counts and ANC monitoring. The following precautionary measures are therefore mandatory and should be carried out in accordance with official recommendations.
Because of the risks associated with DENZAPINE, its use is limited to patients in whom therapy is indicated as set out in section 4.1 (Therapeutic indications) and:
• who have initially normal leukocyte findings (WBC count greater than 3500/mm3 (3.5 x 109/L) and ANC above 2000/mm3 (2.0 x 109/L), and
• in whom regular WBC counts and ANC can be performed weekly for the first 18 weeks and at least 4-week intervals thereafter. Monitoring must continue throughout treatment and for 4 weeks after complete discontinuation of DENZAPINE.
Before initiating clozapine therapy patients should have a blood test (see “agranulocytosis”) and a history and physical examination. Patients with history of cardiac illness or abnormal cardiac findings on physical examination should be referred to a specialist for other examinations that might include an ECG, and the patient treated only if the expected benefits clearly outweigh the risks (see Section 4.3). The treating physician should consider performing a pre-treatment ECG. Caution should be exercised in patients with cardiovascular disease or a family history of QT prolongation.
As with other antipsychotics, caution should be exercised when clozapine is prescribed with medicines known to increase QTc interval
The concomitant administration of neuroleptic medicines should be avoided.
Prescribing physicians should comply fully with the required safety measures.
Prior to treatment initiation, physicians must ensure, to the best of their knowledge, that the patient has not previously experienced an adverse haematological reaction to clozapine that necessitated its discontinuation. Prescriptions should not be issued for periods longer than the interval between two blood counts.
Immediate discontinuation of DENZAPINE is mandatory if either the WBC count is less than 3000/mm3 (3.0 x 109 /L) or the ANC is less than 1500/mm3 (1.5 x 109 /L) at any time during DENZAPINE treatment. Patients in whom DENZAPINE has been discontinued as a result of either WBC or ANC deficiencies must not be re-exposed to DENZAPINE.
At each consultation, a patient receiving DENZAPINE should be reminded to contact the treating physician immediately if any kind of infection begins to develop. Particular attention should be paid to flu-like complaints such as fever or sore throat and to other evidence of infection, which may be indicative of neutropenia. Patients and their caregivers must be informed that, in the event of any of these symptoms, they must have a blood cell count performed immediately. Prescribers are encouraged to keep a record of all patients' blood results and to take any steps necessary to prevent these patients from accidentally being rechallenged in the future.
Patients with a history of primary bone marrow disorders may be treated only if the benefit outweighs the risk. They should be carefully reviewed by a haematologist prior to starting DENZAPINE.
Patients who have low WBC counts because of benign ethnic neutropenia should be given special consideration and may be started on DENZAPINE with the agreement of a haematologist.
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WBC Counts and ANC Monitoring
WBC and differential blood counts must be performed within 10 days prior to initiating DENZAPINE treatment to ensure that only patients with normal WBC counts (WBC count greater than 3500/mm3 (3.5 x 109/L) and ANC above 2000/mm3 (2.0 x 109/L)) will receive the drug. After the start of DENZAPINE treatment the WBC count and ANC must be monitored weekly for the first 18 weeks, and at least at four-week intervals thereafter.
Monitoring must continue throughout treatment and for 4 weeks after complete discontinuation of DENZAPINE or until haematological recovery has occurred (see below Low WBC count/ANC). At each consultation, the patient should be reminded to contact the treating physician immediately if any kind of infection, fever, sore throat or other flu-like symptoms develop. WBC and differential blood counts must be performed immediately if any symptoms or signs of an infection occur.
Low WBC count/ANC
If, during DENZAPINE therapy, either the WBC count falls to between 3500/mm3 (3.5 x 109/L) and 3000/mm3 (3.0 x 109/L) or the ANC falls to between 2000/mm3 (2.0 x 109/L) and 1500/mm3 (1.5 x 109/L), haematological evaluations must be performed at least twice weekly until the patient's WBC count and ANC stabilise within the range 3000-3500/mm3 (3.0 - 3.5 x 109/L) and 1500 - 2000/mm3 (1.5 - 2.0 x 109/L), respectively, or higher.
Immediate discontinuation of DENZAPINE treatment is mandatory if either the WBC count is less than 3000/mm3 (3.0 x 109/L) or the ANC is less than 1500/mm3 (1.5 x 109/L) during DENZAPINE treatment. WBC counts and differential blood counts should then be performed daily and patients should be carefully monitored for flu-like symptoms or other symptoms suggestive of infection. Confirmation of the haematological values is recommended by performing two blood counts on two consecutive days; however, DENZAPINE should be discontinued after the first blood count.
Following discontinuation of DENZAPINE, haematological evaluation is required until haematological recovery has occurred.
Blood cell count
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Action required
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WBC/mm3 (/L)
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ANC/mm3 (/L)
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>3500 (3.5 x 109)
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>2000 (2.0 x 109)
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Continue DENZAPINE treatment
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3000- 3500
(3.0 x 109 - 3.5 x 109)
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1500-2000
(1.5 x 109 - 2.0 x 109)
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Continue DENZAPINE treatment, sample blood twice weekly until counts stabilise or increase
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< 3000 ( < 3.0 x 109)
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< 1500 ( < 1.5 x 109)
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Immediately stop DENZAPINE treatment, sample blood daily until haematological abnormality is resolved, monitor for infection. Do not re-expose the patient.
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If DENZAPINE has been withdrawn and either a further drop in the WBC count below 2000/mm3 (2.0 x 109/L) occurs or the ANC falls below 1000/mm3 (1.0 x 109/L), the management of this condition must be guided by an experienced haematologist.
Discontinuation of therapy for haematological reasons
Patients in whom DENZAPINE has been discontinued as a result of either WBC or ANC deficiencies (see above) must not be re-exposed to DENZAPINE.
Prescribers are encouraged to keep a record of all patients' blood results and to take any steps necessary to prevent the patient being accidentally rechallenged in the future.
Discontinuation of therapy for other reasons
Patients who have been on DENZAPINE for more than 18 weeks and have had their treatment interrupted for more than 3 days but less than 4 weeks should have their WBC count and ANC monitored weekly for an additional 6 weeks. If no haematological abnormality occurs, monitoring at intervals not exceeding 4 weeks may be resumed. If DENZAPINE treatment has been interrupted for 4 weeks or longer, weekly monitoring is required for the next 18 weeks of treatment and the dose should be re-titrated (see section 4.2 Posology and method of administration).
Other precautions
In the event of eosinophilia, discontinuation of DENZAPINE is recommended if the eosinophil count rises above 3000/mm3 (3.0 x 109/L); therapy should be restarted only after the eosinophil count has fallen below 1000/mm3 (1.0 x 109/L).
In the event of thrombocytopenia, discontinuation of DENZAPINE therapy is recommended if the platelet count falls below 50 000/mm3 (50 x 109/L).
Orthostatic hypotension, with or without syncope, can occur during DENZAPINE treatment. Rarely, collapse can be profound and may be accompanied by cardiac and/or respiratory arrest. Such events are more likely to occur with concurrent use of benzodiazepines or any other psychotropic agent (see section 4.5 Interaction with other medicinal products and other forms of interaction) and during initial titration in association with rapid dose escalation; on very rare occasions they may occur even after the first dose. Therefore, patients commencing DENZAPINE treatment require close medical supervision. Monitoring of standing and supine blood pressure is necessary during the first weeks of treatment in patients with Parkinson's disease.
Analysis of safety databases suggests that the use of clozapine is associated with an increased risk of myocarditis especially during, but not limited to, the first two months of treatment. Some cases of myocarditis have been fatal.
Pericarditis/pericardial effusion and cardiomyopathy have also been reported in association with clozapine use; these reports also include fatalities. Myocarditis or cardiomyopathy should be suspected in patients who experience persistent tachycardia at rest, especially in the first two months of treatment, and/or palpitations, arrhythmias, chest pain and other signs and symptoms of heart failure (e.g. unexplained fatigue, dyspnoea, tachypnoea), or symptoms that mimic myocardial infarction. Other symptoms which may be present in addition to the above include flu-like symptoms. If myocarditis or cardiomyopathy are suspected, DENZAPINE treatment should be promptly stopped and the patient immediately referred to a cardiologist.
Patients with clozapine-induced myocarditis or cardiomyopathy should not be re-exposed to DENZAPINE.
Patients with a history of epilepsy should be closely observed during DENZAPINE therapy since dose-related convulsions have been reported. In such cases, the dose should be reduced (see section 4.2 Posology and method of administration) and, if necessary, an anti-convulsant treatment should be initiated.
Patients with stable pre-existing liver disorders may receive DENZAPINE, but need regular liver function tests. Liver function tests should be performed in patients in whom symptoms of possible liver dysfunction, such as nausea, vomiting and/or anorexia, develop during DENZAPINE therapy. If the elevation of the values is clinically relevant (more than 3 times the UNL) or if symptoms of jaundice occur, treatment with DENZAPINE must be discontinued. It may be resumed (see “Re-starting therapy” under section 4.2) only when the results of liver function tests are normal. In such cases, liver function should be closely monitored after re-introduction of the drug.
DENZAPINE exerts anticholinergic activity, which may produce undesirable effects throughout the body. Careful supervision is indicated in the presence of prostatic enlargement and narrow-angle glaucoma. Probably on account of its anticholinergic properties, clozapine has been associated with varying degrees of impairment of intestinal peristalsis, ranging from constipation to intestinal obstruction, faecal impaction and paralytic ileus (see section 4.8 Undesirable effects). On rare occasions these cases have been fatal. Particular care is necessary in patients who are receiving concomitant medications known to cause constipation (especially those with anticholinergic properties such as some antipsychotics, antidepressants and antiparkinsonian treatments), have a history of colonic disease or a history of lower abdominal surgery as these may exacerbate the situation. It is vital that constipation is recognised and actively treated.
During DENZAPINE therapy, patients may experience transient temperature elevations above 38°C, with the peak incidence within the first 3 weeks of treatment. This fever is generally benign. Occasionally, it may be associated with an increase or decrease in the WBC count. Patients with fever should be carefully evaluated to rule out the possibility of an underlying infection or the development of agranulocytosis. In the presence of high fever, the possibility of neuroleptic malignant syndrome (NMS) must be considered.
Impaired glucose tolerance and/or development or exacerbation of diabetes mellitus has been reported rarely during treatment with clozapine. A mechanism for this possible association has not yet been determined. Cases of severe hyperglycaemia with ketoacidosis or hyperosmolar coma have been reported very rarely in patients with no prior history of hyperglycaemia, some of which have been fatal. When follow-up data were available, discontinuation of clozapine resulted mostly in resolution of the impaired glucose tolerance, and reinstitution of clozapine resulted in its reoccurrence. The discontinuation of clozapine should be considered in patients where active medical management of their hyperglycaemia has failed.
Since DENZAPINE may be associated with thromboembolism, immobilisation of patients should be avoided.
Cases of venous thromboembolism (VTE) have been reported with antipsychotic drugs. Since patients treated with antipsychotics often present with acquired risk factors for VTE, all possible risk factors for VTE should be identified before and during treatment with DENZAPINE and preventive measures undertaken
Use in the elderly
Initiation of treatment in the elderly is recommended at a lower dose (see section 4.2 Posology and method of administration).
Orthostatic hypotension can occur with DENZAPINE treatment and there have been reports of tachycardia, which may be sustained. Elderly patients, particularly those with compromised cardiovascular function, may be more susceptible to these effects.
Elderly patients may also be particularly susceptible to the anticholinergic effects of DENZAPINE, such as urinary retention and constipation.
An approximately 3-fold increased risk of cerebrovascular adverse events has been seen in randomised placebo controlled clinical trials in the dementia population with some atypical antipsychotics. The mechanism for this increased risk is not known. An increased risk cannot be excluded for other antipsychotics or other patient populations. Clozapine should be used with caution in patients with risk factors for stroke.
Increased mortality in elderly people with dementia:
Data from two large observational studies showed that elderly people with dementia who are treated with antipsychotics are at a small increased risk of death compared with those who are not treated. There are insufficient data to give a firm estimate of the precise magnitude of the risk and the cause of the increased risk is not known.
DENZAPINE is not approved for the treatment of dementia-related behavioural disturbances.
4.5 Interaction With Other Medicinal Products And Other Forms Of Interaction
Contraindication of concomitant use
Drugs known to have a substantial potential to depress bone marrow function should not be used concurrently with DENZAPINE (see section 4.3 Contraindications). These include co-trimoxazole, chloramphenicol, sulphonamides, pyrazolone analgesics e.g. phenylbutazone, penicillamine, carbamazepine or cytotoxic agents.
Long-acting depot antipsychotics (which have myelosuppressive potential) should not be used concurrently with DENZAPINE because these cannot be rapidly removed from the body in situations where this may be required, e.g. neutropenia (see section 4.3 Contraindications).
Alcohol should not be used concomitantly with DENZAPINE due to possible potentiation of sedation.
Precautions including dose adjustment
DENZAPINE may enhance the central effects of CNS depressants such as narcotics, antihistamines, and benzodiazepines. Particular caution is advised when DENZAPINE therapy is initiated in patients who are receiving a benzodiazepine or any other psychotropic drug. These patients may have an increased risk of circulatory collapse, which, on rare occasions, can be profound and may lead to cardiac and/or respiratory arrest. It is not clear whether cardiac or respiratory collapse can be prevented by dose adjustment.
Because of the possibility of additive effects, caution is essential in the concomitant administration of drugs possessing anticholinergic, hypotensive, or respiratory depressant effects.
Owing to its anti-α-adrenergic properties, DENZAPINE may reduce the blood-pressure-increasing effect of norepinephrine or other predominantly α-adrenergic agents and reverse the pressor effect of epinephrine.
Concomitant administration of drugs known to inhibit the activity of some cytochrome P450 isozymes may increase the levels of clozapine, and the dose of clozapine may need to be reduced to prevent undesirable effects. This is more important for CYP 1A2 inhibitors such as caffeine (see below) and the selective serotonin reuptake inhibitors fluvoxamine and (more controversial) paroxetine. Some of the other serotonin reuptake inhibitors such as fluoxetine, paroxetine and to a lesser degree sertraline are CYP 2D6 inhibitors and, as a consequence, major pharmacokinetic interactions with clozapine are less likely. Similarly, pharmacokinetic interactions with CYP 3A4 inhibitors such as azole antimycotics, cimetidine, erythromycin, and protease inhibitors are unlikely, although some have been reported. Because the plasma concentration of clozapine is increased by caffeine intake and decreased by nearly 50% following a 5-day caffeine-free period, dosage changes of clozapine may be necessary when there is a change in caffeine-drinking habit. In cases of sudden cessation of smoking, the plasma clozapine concentration may be increased, thus leading to an increase in adverse effects.
Cases have been reported of an interaction between citalopram and clozapine, which may increase the risk of adverse events associated with clozapine. The nature of this interaction has not been fully elucidated.
Concomitant administration of drugs known to induce cytochrome P450 enzymes may decrease the plasma levels of clozapine, leading to reduced efficacy. Drugs known to induce the activity of cytochrome P450 enzymes and with reported interactions with clozapine include, for instance, carbamazepine (not to be used concomitantly with clozapine, due to its myelosuppresive potential), phenytoin and rifampicin. Known inducers of CYP1A2 such as omeprazole, may lead to decreased clozapine levels. The potential for reduced efficacy of clozapine should be considered when it is used in combination with these drugs.
Others
Concomitant use of lithium or other CNS-active agents may increase the risk of development of neuroleptic malignant syndrome (NMS).
Concomitant use of clozapine with drugs known to prolong the QT interval may increase the risk of ventricular arrhythmias, including Torsades de pointes. Therefore concomitant use of these products is not recommended. Examples include certain antiarrhythmics, such as those of Class 1A (such as quinidine, disopyramide and procainamide) and Class III (such as amiodarone, sotalol and dofetilide), certain antimicrobials (sparfloxacin, moxifloxacin, erythromycin IV), tricyclic antidepressants (such as amitriptyline), certain tetracyclic antidepressants (such as maprotiline), other neuroleptics (e.g. phenothiazines, pimozide, sertindole and haloperidol), certain antihistamines (such as terfenadine), cisapride, bretylium and certain antimalarials such as quinine and mefloquine. This list is not comprehensive.
Concurrent use of drugs causing electrolyte imbalance is not recommended. Diuretics, in particular those causing hypokalemia, should be avoided but, if necessary, potassium-sparing diuretics are preferred.
Rare but serious reports of seizures, including onset of seizures in non-epileptic patients, and isolated cases of delirium where DENZAPINE was co-administered with valproic acid have been reported. These effects are possibly due to a pharmacodynamic interaction, the mechanism of which has not been determined.
Caution is called for in patients receiving concomitant treatment with other drugs which are either inhibitors or inducers of the cytochrome P450 isozymes. With tricyclic antidepressants, phenothiazines and type IC anti-arrhythmics, which are known to bind to cytochrome P450 2D6, no clinically relevant interactions have been observed thus far.
An outline of drug interactions believed to be most important with DENZAPINE is given in Table 1 below (this is not an exhaustive list).
Table 1: Reference to the most common drug interactions with DENZAPINE
Drug
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Interactions
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Comments
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Bone marrow suppressants (e.g. carbamazapine, chloramphenicol, sulphonamides (e.g. co-trimoxazole), pyrazolone analgesics (e.g. phenylbutazone), penicillamine, cytotoxic agents and long-acting depot injections of antipsychotics
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Interact to increase the risk and/or severity of bone marrow suppression
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DENZAPINE should not be used concomitantly with other agents having a well known potential to suppress bone marrow function (see Section 4.3 Contraindications )
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Benzodiazepines
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Concomitant use may increase risk of circulatory collapse, which may lead to cardiac and/or respiratory arrest
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Whilst the occurrence is rare, caution is advised when using these drugs together. Reports suggest that respiratory depression and collapse are more likely to occur at the start of this combination or when DENZAPINE is added to an established benzodiazepine regimen.
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Anticholinergics
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DENZAPINE potentiates the action of these drugs through additive anticholinergic activity
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Observe patients for anticholinergic side - effects, e.g. constipation, especially when using to help control hypersalivation
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Antihypertensives
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DENZAPINE can potentiate the hypotensive effects of these drugs due to its sympathomimetic antagonistic effects
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Caution is advised if DENZAPINE is used concomitantly with antihypertensive agents. Patients should be advised of the risk of hypotension, especially during the period of initial dose titration
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Alcohol, MAOIs, CNS depressants, including narcotics and benzodiazepines
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Enhanced central effects. Additive CNS depression and cognitive and motor performance interference when used in combination with these drugs
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Caution is advised if DENZAPINE is used concomitantly with other CNS active agents. Advise patients of the possible additive sedative effects and caution them not to drive or operate machinery
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Highly protein bound drugs
(e.g. warfarin and digoxin)
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DENZAPINE may cause an increase in plasma concentration of these drugs due to displacement from plasma proteins
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Patients should be monitored for the occurrence of side effects associated with these drugs, and doses of the protein bound drug adjusted, if necessary
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Phenytoin
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Addition of phenytoin to DENZAPINE drug regimen may cause a decrease in the clozapine plasma concentrations
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If phenytoin must be used, the patient should be monitored closely for a worsening or recurrence of psychotic symptoms
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Lithium
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Concomitant use can increase the risk of development of neuroleptic malignant syndrome (NMS)
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Observe for signs and symptoms of NMS
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CYP1A2 inducing substances (e.g. omeprazole)
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Concomitant use may decrease clozapine levels
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Potential for reduced efficacy of clozapine should be considered.
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CYP1A2 inhibiting substances (e.g. fluvoxamine, caffeine, ciprofloxacin)
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Concomitant use may increase clozapine levels
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Potential for increase in adverse effects. Care is also required upon cessation of concomitant CYP1A2 inhibiting medications as there will be a decrease in clozapine levels.
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4.6 Pregnancy And Lactation
Pregnancy
For clozapine, there are only limited clinical data on exposed pregnancies. Animal studies do not indicate direct or indirect harmful effects with respect to pregnancy, embryonal/foetal development, parturition or postnatal development (see 5.3). Caution should be exercised when prescribing to pregnant women.
Lactation
Animal studies suggest that clozapine is excreted in breast milk and has an effect in the nursing infant; therefore, mothers receiving DENZAPINE should not breast-feed.
Women of child-bearing potential
A return to normal menstruation may occur as a result of switching from other antipsychotics to DENZAPINE. Adequate contraceptive measures must therefore be ensured in women of childbearing potential.
4.7 Effects On Ability To Drive And Use Machines
Owing to the ability of DENZAPINE to cause sedation and lower the seizure threshold, activities such as driving or operating machinery should be avoided, especially during the initial weeks of treatment.
4.8 Undesirable Effects
For the most part, the adverse event profile of clozapine is predictable from its pharmacological properties. An important exception is its propensity to cause agranulocytosis (see section 4.4 Special warnings and precautions for use). Because of this risk, its use is restricted to treatment-resistant schizophrenia and psychosis occurring during the course of Parkinson's disease in cases where standard treatment has failed. While blood monitoring is an essential part of the care of patients receiving clozapine, the physician should be aware of other rare but serious adverse events, which may be diagnosed in the early stages only by careful observation and questioning of the patient in order to prevent morbidity and mortality.
Blood and lymphatic system
Development of granulocytopenia and agranulocytosis is a risk inherent to DENZAPINE treatment. Although generally reversible on withdrawal of treatment, agranulocytosis may result in sepsis and can prove fatal. Because immediate withdrawal of the drug is required to prevent the development of life-threatening agranulocytosis, monitoring of the WBC count is mandatory (see section 4.4 Special warnings and precautions for use). Table 2 below summarises the estimated incidence of agranulocytosis for each DENZAPINE treatment period.
Table 2: Estimated incidence of agranulocytosis1
Treatment period
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Incidence of agranulocytosis per 100,000 person-weeks2 of observation
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Weeks 0 - 18
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32.0
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Weeks 19 - 52
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2.3
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Weeks 53 and higher
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