Dopamine-regulating drugs.

Tetrabenazine

Each tablet contains 25mg Tetrabenazine.

Tablet

Movement disorders associated with organic central nervous system conditions, e.g. Huntington's chorea, hemiballismus and senile chorea. Xenazine™ 25 is also indicated for the treatment of moderate to severe tardive dyskinesia, which is disabling and/or socially embarrassing. The condition should be persistent despite withdrawal of antipsychotic therapy, or in cases where withdrawal of antipsychotic medication is not a realistic option; also where the condition persists despite reduction in dosage of antipsychotic medication or switching to atypical antipsychotic medication.

The tablets are for oral administration.

 Organic Central Nervous System Movement Disorders

Adults

Dosage and administration are variable and only a guide is given. An initial starting dose of 25mg three times a day is recommended. This can be increased by 25mg a day every three or four days until 200mg a day is being given or the limit of tolerance, as dictated by unwanted effects, is reached, whichever is the lower dose.

If there is no improvement at the maximum dose in seven days, it is unlikely that the compound will be of benefit to the patient, either by increasing the dose or by extending the duration of treatment.

Tardive Dyskinesia

Recommended starting dose of 12.5mg a day, subsequently titrated according to response. Medication should be discontinued if there is no clear benefit or if the side-effects cannot be tolerated

No specific dosage recommendations are made for the administration of Xenazine™ 25 to children, although it has been used without ill effect.

No specific studies have been performed in the elderly, but Xenazine™ 25 has been administered to elderly patients in standard dosage without apparent ill effect.

Xenazine™ 25 blocks the action of reserpine

Tardive Dyskinesia

The condition should be persistent despite withdrawal of antipsychotic therapy, or in cases where withdrawal of antipsychotic medication is not a realistic option; also where the condition persists despite reduction in dosage of antipsychotic medication or switching to atypical antipsychotic medication.

Levodopa should be administered with caution in the presence of Xenazine™ 25 .

Side-effects are usually mild with little hypotensive action and few digestive disorders. The main unwanted effect reported to date has been drowsiness, which occurs with higher doses. If depression occurs, it can be controlled by reducing the dose or by giving antidepressant drugs such as the monoamine oxidase inhibitors. However, Xenazine™ 25 should not be given immediately after a course of any of the monoamine oxidase inhibitors as such treatment may lead to a state of restlessness, disorientation and confusion. In man, a Parkinsonian-like syndrome has been reported on rare occasions, usually in doses above 200mg per day, but this disappears on reducing the dose.

Neuroleptic malignant syndrome (NMS) associated with the use of Tetrabenazine has been reported rarely. This may occur soon after initiation of therapy, following an increase in dosage or after prolonged treatment. The clinical features usually include hyperthermia, severe extrapyramidal symptoms including muscular rigidity, autonomic dysfunction and altered levels of consciousness. Skeletal muscle damage may occur. If NMS is suspected Xenazine™ 25 should be withdrawn and appropriate supportive therapy instituted; treatment with Dantrolene and Bromocriptine may be effective.

Cambridge Laboratories

(POM)

25 March 2009