Drug Description

Presentation

Indications

Adult Dosage

Route of administration: oral.

There is considerable inter-patient variation in the dosage requirements and the dosage should be individualised to meet the needs and response of each patient. In determining the initial dose, consideration should be given to the patient's age, severity of symptoms and any previous response to other anti-psychotic therapy. The dosage may be administered in single or divided doses; administration twice daily is usually sufficient.

Adults:

Psychotic conditions, behavioural or mental disorders, moderate to severe psychomotor agitation or impulsive behaviour.

The usual initial dosage ranges from 1.5 to 20mg daily, depending on the individual patient's characteristics and the severity of symptoms. It may be necessary to increase the dosage, gradually, to obtain adequate control of symptoms. The maximum daily dose should not exceed 30mg.

The usual maintenance dosage ranges from 3 to 10mg daily, and this may be achieved by gradually reducing the dosage to the lowest effective maintenance level.

Gilles de la Tourette's syndrome.

The initial dosage is usually 2mg daily. This may be increased, gradually, during the acute phase of treatment and in order to obtain maximum control of symptoms a dosage of 6 to 30mg daily may be required.

When a satisfactory response has been achieved, the dosage should be gradually reduced to the lowest effective maintenance level, which is 4mg daily for most patients.

Elderly:

Half the recommended adult starting dose may be sufficient for therapeutic response. As elderly or debilitated patients may be much more sensitive to haloperidol, the maximum and maintenance doses will generally be lower.

Anxiety.

0.5mg twice daily.

Childhood behavioural disorders and schizophrenia

Total daily maintenance dose of 0.025-0.05 mg (25 to 50 micrograms)/kg body weight per day, up to a maximum of 10 mg daily. Half the dose should be given in the morning and the other half in the evening.

Gilles de la Tourette syndrome

Oral maintenance doses of up to 10 mg/day in most patients.

Adjunct to the short-term management of anxiety

Not recommended

Contra Indications

Comatose states: Parkinson's disease; hypersensitivity to haloperidol; breast-feeding, lesions of basal ganglia, clinically significant cardiac disorders (e.g. Recent acute myocardial infarction, uncompensated heart failure, arrhythmias treated with class IA and III antiarrhythmic medicinal products), QTc interval prolongation, history of ventricular arrhythmia or Torsades de pointes, uncorrected hypokalaemia and other QT prolonging drugs.

Special Precautions

Care is required when administering haloperidol to patients with hepatic disease, renal failure, phaeochromocytoma, conditions predisposing to epilepsy (e.g. alcohol withdrawal or brain damage). Haloperidol may be given to patients with epilepsy but usual anticonvulsant therapy should be continued.

Caution is required when using haloperidol in thyrotoxic patients and those with arteriosclerosis who may have occult or manifest lesions of the basal ganglia; such patients may be more prone to develop extrapyramidal symptoms.

Haloperidol should be used with care in patients with severe cardiovascular disorders, because of the possibility of transient hypotension. Should hypotension occur and a vasopressor be required, adrenaline should not be used since haloperidol may block its vasopressor activity and paradoxical further lowering of the blood pressure may occur.

Cases of sudden death have been reported in psychiatric patients receiving antipsychotic drugs, including haloperidol.

There is an increased risk of arrhythmias when antipsychotics are given with other drugs that prolong the QT interval. Those receiving concomitant therapy with such drugs should be monitored carefully (ECGs and potassium levels).

Abrupt withdrawal of antipsychotic drugs after long-term therapy may be associated with acute withdrawal symptoms including nausea, vomiting and insomnia. Withdrawal from antipsychotics should always be gradual and closely monitored to avoid the risk of acute withdrawal syndromes or rapid relapse.

Like all other antipsychotic agents, haloperidol should not be used alone where depression is predominant. It may be combined with antidepressants to treat those conditions in which depression and psychosis co-exist. It must be kept in mind that antipsychotics are reported to increase plasma concentration of tricyclics, possibly increasing the risk of ventricular arrhythmias

Haloperidol may impair the antiparkinson effects of levodopa. If an antiparkinson agent is used concomitantly with haloperidol, both drugs should not be discontinued simultaneously, since extrapyramidal symptoms, previously controlled by antiparkinson agents, may occur due to the slower excretion rate of haloperidol.

The physician should keep in mind the possibility of additive antimuscarinic effects when haloperidol is used with antiparkinson drugs with antimuscarinic effects. Concomitant use of two or more drugs having antimuscarinic effects can increase side-effects such as dry mouth, urine retention, and constipation.

The risk-benefit of haloperidol treatment should be fully assessed before treatment is commenced and patients with risk factors for ventricular arrhythmias such as cardiac disease, family history of sudden death and/or QT prolongation; uncorrected electrolyte disturbances; subarachnoid haemorrhage, starvation or alcohol abuse should be monitored carefully (ECGs and potassium levels), particularly during the initial phase of treatment to obtain steady plasma levels.

Haloperidol should be used in caution in patients known to be slow metabolisers of CYP2D6, and during the use of cytochrome P450 inhibitors. Concomitant use of anti-psychotics should be avoided.

Baseline ECG is recommended prior to treatment in all patients, especially in the elderly and patients with a positive personal or family history of cardiac diseases or abnormal findings on cardiac clinical examination. During therapy, the need for ECG monitoring (e.g. at dose escalation) should be assessed on an individual basis. Whilst on therapy, the dose should be reduced if QT is prolonged, and haloperidol should be discontinued if the QTc exceeds 500ms.

Periodic electrolyte monitoring is recommended, especially for patients taking diuretics, or during intercurrent illness.

Interactions

Following interactions have been reported with haloperidol:

Adrenergic blocking agents: Haloperidol may reverse the blood-pressure-lowering effects of adrenergic-blocking agents such as guanethidine.

Antiarrhythmics & other drugs that prolong QT interval: There is increased risk of ventricular arrhythmias when antipsychotics that prolong the QT interval given with anti-arrhythmics that prolong the QT interval. Concomitant use of haloperidol with amiodarone should be avoided. Amiodarone has a long half-life; there is a potential for drug interactions to occur for several weeks (or even months) after treatment with it has been stopped.

Anticonvulsant: Antipsychotics antagonise anticonvulsant effect of drugs such as carbamazepine, phenytoin, primidone which can result in lowering of convulsive threshold. Dosage of anticonvulsants may need to be increased.

Antimuscarinic drugs: Effects of haloperidol may be reduced by these drugs. There is also a possibility of increase in side-effects such as dry mouth, urine retention, and constipation due to additive antimuscarinic effects; concomitant use can also lead to confusion in the elderly.

Antidepressants, tricyclics: Haloperidol may impair the metabolism of tricyclic antidepressants and increase plasma concentration of tricyclics, possibly increasing risk of ventricular arrhythmia

CNS depressants: Haloperidol may enhance the central nervous system depressant effects of other CNS-depressant drugs including alcohol, hypnotics, sedatives or strong analgesics.

Enzyme inducers: Co-administration of enzyme-inducing drugs such as carbamazepine, phenobarbitone and rifampicin with haloperidol may result in a significant reduction of haloperidol plasma levels. Haloperidol dose may therefore need to be increased, according to the patient's response. After stopping such drugs, it may be necessary to re-adjust the dosage of haloperidol.

Levodopa: Haloperidol may impair the antiparkinson effects of levodopa.

Lithium: In rare cases, an encephalopathy-like syndrome has been reported in combination with lithium and haloperidol. Signs of encephalopathy-like syndrome include confusion, disorientation, headache, disturbances of balance and drowsiness. When lithium and haloperidol therapy are used concomitantly, haloperidol should be given in the lowest effective dose and lithium levels should be monitored and kept below 1 mmol/l. If symptoms of encephalopathy-like syndrome occur, therapy should be stopped immediately.

Methyldopa: Enhanced CNS effects have been reported when haloperidol is used in combination with methyldopa.

Phenindione: Antagonism of the effect of phenindione has been reported.

Sympathomimetics: Haloperidol may antagonize the action of adrenaline and other sympathomimetic agents.

In pharmacokinetic studies, increased haloperidol levels have been reported when haloperidol was given concomitantly with the following drugs: quinidine, buspirone and fluoxetine. Haloperidol plasma levels should therefore be monitored and reduced if necessary.

Use of haloperidol with concomitant QT prolonging drugs could induce torsade de pointes and is contraindicated. These include class IA and III anti arrhythmics, neuroleptics, antidepressive agents (tricyclics and venlafaxine), certain antibiotics including some agents of the following classes: macrolides, fluoroquinolones, imidazole, and triazole antifungal agents, antimalarials, certain non-sedating antihistaminics (terfenadine, astemizole), 5-HT3 receptor antagonists, arsenic trioxide.

Concomitant use of drugs that cause electrolyte imbalance or that are metabolic inhibitors of cytochrome CYP2D6 may increase the risk of ventricular arrhythmias. If the benefit is considered to outweigh the risk in the individual patient, co-administration should be undertaken with caution and ECG monitoring should be considered.

Adverse Reactions

Central Nervous System: In common with all neuroleptics, extrapyramidal symptoms may occur, e.g. tremor, oculogyric crisis and laryngeal dystonia. Anti- Parkinson agents should not be prescribed routinely.

As with all antipsychotics agents, tardive dyskinesia may appear in some patients on long term therapy or after drug discontinuation. The syndrome is mainly characterised by rhythmical involuntary movements of the tongue, face, mouth or jaw. The manifestations may be permanent in some patients. The syndrome may be masked when treatment is reinstituted, when the dosage is increased or when a switch is made to a different antipsychotic drug. Treatment should be discontinued as soon as possible. However, since its occurrence may be related to duration of treatment, as well as daily dose, Haldol should be given in the minimum effective dose for the minimum possible time, unless it is established that long term administration for the treatment of schizophrenia is required.

It has been reported that fine vermicular movements of the tongue may be an early warning sign of tardive dyskinesia and that the full syndrome may not develop if the medication is stopped at that time.

The following effects have been reported rarely; confusional states or epileptic fits, depression, sedation, agitation, insomnia, headache, vertigo and apparent exacerbation of psychotic symptoms.

In common with other antipsychotic drugs, haloperidol has been associated with neuroleptic malignant syndrome (NMS). An idiosyncratic response characterised by hyperthermia, generalised muscle rigidity, autonomic instability, altered consciousness, coma and elevated CPK. Signs of autonomic dysfunction such as tachycardia, labile arterial pressure and sweating may precede onset of hyperthermia, acting as early warning signs. Antipsychotic treatment should be withdrawn immediately and appropriate supportive therapy and careful monitoring instituted. Haloperidol, even in low dosage in susceptible (especially non-psychotic) individuals may cause unpleasant subjective feelings of being mentally dulled or slowed down, dizziness, headache or paradoxical effects of excitement, agitation or insomnia.

Gastro-intestinal System: gastro-intestinal symptoms, nausea, loss of appetite, constipation and dyspepsia have been reported.

Endocrinal System: Hormonal effects of antipsychotic neuroleptic drugs include hyperprolactinaemia, which may cause galactorrhoea, gynaecomastia and oligo- or amenorrhoea. Hypoglycaemia and the syndrome of inappropriate antidiuretic hormone secretion have been reported rarely. Impairment of sexual function including erection and ejaculation has also been occasionally reported.

Cardiovascular System: Tachycardia and dose related hypotension are uncommon, but can occur, particularly in the elderly, who are more susceptible to the sedative and hypotensive effects. Less commonly, hypertension has also been reported.

Cardiac effects such as QT-interval prolongation, Torsade de Pointes, ventricular arrhythmias, including ventricular fibrillation and ventricular tachycardia and cardiac arrest have been reported rarely. Cases of sudden unexpected death have also occurred. These effects may occur more frequently with high doses, intravenous administration and in predisposed patients ( see 4.4. Special Warnings and Special Precautions for use).

Autonomic Nervous System: Dry mouth as well as excessive salivation, blurred vision, urinary retention and hyperhidrosis have been reported.

Other Adverse Reactions: The following effects have been reported rarely: Jaundice, cholestatic hepatitis, or transient abnormalities of liver function in the absence of jaundice; priapism and weight changes. Temperature disorders may also occur, characteristically hyperthermia associated with NMS, although hypothermia has also been reported. The following have been reported very rarely: blood dyscrasia, including agranulocytosis, thrombocytopenia and transient leucopenia, hypersensitivity reactions including anaphylaxis.

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