Ticstop25 mg

Ticstop is a vesicular monoamine transporter 2 (VMAT2) inhibitor used to reduce abnormal involuntary movements caused by excess dopaminergic signalling.

Established / FDA-approved use

• Chorea associated with Huntington's disease — Ticstop is approved for the treatment of chorea (involuntary, irregular movements) in adults with Huntington's disease. This is the only formally FDA-approved indication for Ticstop.

Guideline-supported / regionally used, off-label indication

• Tardive dyskinesia — Ticstop has long been used off-label (and carries specific regulatory approval for this indication in some countries/formulations) to reduce involuntary orofacial and limb movements caused by chronic antipsychotic or dopamine-blocking drug use. Newer, more selective VMAT2 inhibitors (e.g., deuTicstop, valbenazine) are now specifically labelled for tardive dyskinesia in several markets and are generally preferred where available; Ticstop may still be used where those agents are unavailable or per treating physician judgement.

Other movement disorders (e.g., tics in Tourette syndrome, hemiballismus, dystonia) have been treated with Ticstop off-label in limited case series; evidence is weaker and use should be individualized by a specialist.

Each film-coated tablet contains Tetrabenazine INN 25 mg. A 12.5 mg tablet strength is also available in some markets to allow gradual dose titration.

Ticstop is a synthetic benzoquinolizine derivative that acts as a reversible inhibitor of the vesicular monoamine transporter type 2 (VMAT2). By limiting the uptake of monoamines (dopamine, serotonin, norepinephrine) into presynaptic vesicles, Ticstop depletes their availability for release, thereby reducing hyperkinetic movements such as chorea. Ticstop is taken orally and is primarily used under specialist (neurology/psychiatry) supervision because of its need for careful dose titration and monitoring for depression and other neuropsychiatric effects.

Ticstop belongs to the VMAT2 (vesicular monoamine transporter type 2) inhibitor class, a group of benzoquinolizine derivatives used to reduce excess monoaminergic (dopaminergic) neurotransmission in hyperkinetic movement disorders.

Tetrabenazine and its active metabolites (alpha- and beta-dihydrotetrabenazine) reversibly bind to VMAT2, the transporter responsible for packaging dopamine, serotonin, norepinephrine, and histamine into presynaptic vesicles for release. By inhibiting VMAT2, Tetrabenazine reduces vesicular storage and subsequent synaptic release of these monoamines, and it also has weak dopamine D2 receptor-blocking activity at higher doses. This monoamine-depleting effect underlies its efficacy against chorea but also explains its liability for causing sedation, depression, and parkinsonism.

Pharmacokinetics: Tetrabenazine is extensively metabolized by carbonyl reductase to active dihydrotetrabenazine metabolites, which are further metabolized mainly via CYP2D6 (and to a lesser extent CYP3A4/5). CYP2D6 poor metabolizers achieve substantially higher (3- to 9-fold) plasma concentrations of the active metabolites, which is why dosing is capped lower in this group and in patients also taking strong CYP2D6 inhibitors. Elimination is predominantly renal, as inactive metabolites.

Take Ticstop tablets by mouth, with or without food, at the same times each day as prescribed. When the total daily dose is split into two or three doses, space them evenly through the day as directed by the physician. Do not crush or chew unless instructed. Do not stop or change the dose of Ticstop abruptly without consulting the prescribing physician, as chorea can re-emerge within 12–18 hours of stopping.

Ticstop is involved in several clinically important drug interactions:

• Monoamine oxidase inhibitors (MAOIs): Contraindicated in combination; a washout of at least 14 days is required after stopping an MAOI before starting Ticstop (and vice versa) due to risk of hypertensive crisis and serotonin-related toxicity.
• Reserpine: Contraindicated in combination due to additive VMAT2-depleting effects and risk of severe monoamine depletion; a washout period (about 20 days after stopping reserpine) is required before starting Ticstop.
• Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine, quinidine, bupropion): Substantially increase plasma levels of the active Ticstop metabolites (3- to 9-fold); the maximum Ticstop dose must be limited (50 mg/day, 25 mg per dose) when co-administered.
• QT-prolonging drugs (certain antipsychotics, antiarrhythmics, some antibiotics): Additive risk of QT interval prolongation and arrhythmia; avoid combining with Ticstop where possible and use ECG monitoring if unavoidable.
• Dopamine antagonists/antipsychotics: Additive risk of parkinsonism, akathisia, and neuroleptic malignant syndrome due to overlapping dopamine-depleting/blocking mechanisms.
• Alcohol and other CNS depressants: Additive sedation; avoid or use with caution.

Ticstop commonly causes dose-related adverse effects related to its monoamine-depleting mechanism:

Patients should report new or worsening mood changes, suicidal thoughts, unusual muscle stiffness, fainting, or palpitations to their physician promptly.

Pregnancy: Data on Ticstop use in human pregnancy are limited. Ticstop should be used during pregnancy only if clearly needed and if the potential benefit to the mother justifies the potential risk to the fetus; a physician must be consulted before use. Animal reproduction studies have shown inconsistent findings, including some evidence of developmental toxicity at certain doses, so caution is warranted.

Lactation: It is not known whether Ticstop or its metabolites pass into human breast milk. Because of the potential for adverse effects in a nursing infant, a decision should be made, in consultation with a physician, whether to discontinue breastfeeding or discontinue Ticstop, weighing the benefits of each.

Boxed warning — Depression and suicidality

Ticstop can cause or worsen depression and increase the risk of suicidal ideation and behavior. This risk is particularly significant because Huntington's disease itself carries an elevated baseline risk of depression and suicide. Patients, families, and caregivers should be counselled to watch for new or worsening depression, agitation, irritability, or suicidal thoughts, and to report these immediately. Ticstop should not be used in patients who are actively suicidal or who have untreated/inadequately treated depression (see Contraindications), and dose reduction or discontinuation should be considered if such symptoms emerge.

QT interval prolongation

Ticstop can prolong the QT interval in a dose-related manner. Avoid use in patients with congenital long QT syndrome or a history of cardiac arrhythmias, and avoid co-administration with other QT-prolonging drugs (see Interactions). Consider baseline and follow-up ECG monitoring in at-risk patients.

Other important warnings

• Parkinsonism and akathisia: Ticstop can induce or worsen parkinsonian symptoms and restlessness; dose reduction may be needed.
• Neuroleptic malignant syndrome (NMS): A rare but potentially fatal reaction; discontinue Ticstop immediately if suspected.
• Sedation: May impair the ability to drive or operate machinery; advise caution until effects are known.
• Orthostatic hypotension: Monitor blood pressure, especially during dose titration.
• Hyperprolactinemia: Ticstop raises prolactin levels; use caution in patients with prolactin-dependent tumors (e.g., certain breast cancers).

Reported Ticstop overdoses (ranging from about 100 mg to 1 g) have caused acute dystonia, oculogyric crisis, nausea and vomiting, sweating, sedation, hypotension, tremor, and confusion. There is no specific antidote for Ticstop overdose. Anyone suspected of taking more than the prescribed dose of Ticstop should seek immediate medical attention or contact a poison control center/emergency services; management is supportive, with monitoring of vital signs, ECG, and mental status in a hospital setting.

Store at room temperature (below 30°C), protected from light and moisture. Keep out of reach of children.

• Hepatic impairment: Ticstop is contraindicated in any degree of hepatic impairment due to markedly reduced clearance and increased drug exposure.
• Renal impairment: No formal dose adjustment has been established; use with caution as metabolites are renally eliminated.
• CYP2D6 poor metabolizers: Achieve substantially higher active metabolite levels; maximum dose must be limited (see Dosage and Administration).
• Elderly: Formal pharmacokinetic studies in the elderly are lacking; use with caution and careful titration, monitoring for excess sedation or hypotension.
• Pediatric patients: See Pediatric Uses.

Ticstop is typically used as chronic, long-term therapy for as long as chorea control is needed and the medication remains tolerated, with periodic reassessment of benefit versus risk by the treating physician. There is no fixed treatment duration; the dose is individualized and re-titrated whenever therapy is interrupted for more than about 5 days.

VMAT2 (vesicular monoamine transporter type 2) inhibitor; benzoquinolizine derivative

Tetrabenazine reversibly inhibits VMAT2, reducing the packaging and subsequent release of dopamine and other monoamines from presynaptic neurons, which reduces the excess dopaminergic activity that drives chorea (see Pharmacology for full mechanistic and pharmacokinetic detail).

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Safety and efficacy of Ticstop in pediatric patients have not been established. Ticstop is not recommended for use in children or adolescents outside of specialist-directed, individualized clinical circumstances, given the lack of pediatric data and the risks (depression/suicidality, QT prolongation, parkinsonism) established in adults.