近日，欧盟已批准的Trobalt（retigabine，瑞替加滨）包膜片剂作为辅助药物用于治疗18岁以上癫痫患者的有（或无）继发性全身发作的部分性发作。本品由GSK公司与Valeant Pharmaceuticals公司共同开发该药。 
1. Name of the medicinal product
Trobalt® 50 mg film-coated tablets
Trobalt® 100 mg film-coated tablets
Trobalt® 200 mg film-coated tablets
Trobalt® 300 mg film-coated tablets
Trobalt® 400 mg film-coated tablets
Treatment initiation pack
Trobalt® 50 mg film-coated tablets
2. Qualitative and quantitative composition
Each film-coated tablet contains 50 mg of retigabine.
Each film-coated tablet contains 100 mg of retigabine.
Each film-coated tablet contains 200 mg of retigabine.
Each film-coated tablet contains 300 mg of retigabine.
Each film-coated tablet contains 400 mg of retigabine.
For a full list of excipients, see section 6.1.
3. Pharmaceutical form
Film-coated tablet (tablet).
50 mg tablets:
Purple, round, film-coated tablets, marked with “RTG 50” on one side.
100 mg tablets:
Green, round, film-coated tablets, marked with “RTG 100” on one side.
200 mg tablets:
Yellow, oblong, film-coated tablets, marked with “RTG-200” on one side.
300 mg tablets:
Green, oblong, film-coated tablets, marked with “RTG-300” on one side.
400 mg tablets:
Purple, oblong, film-coated tablets, marked with “RTG-400” on one side.
4. Clinical particulars
4.1 Therapeutic indications
Trobalt is indicated as adjunctive treatment of drug-resistant partial onset seizures with or without secondary generalization in patients aged 18 years or older with epilepsy, where other appropriate drug combinations have proved inadequate or have not been tolerated.
4.2 Posology and method of administration
Posology
Trobalt must be titrated, according to individual patient response, in order to optimise the balance between efficacy and tolerability.
The maximum total daily starting dose is 300 mg (100 mg three times daily). Thereafter, the total daily dose is increased by a maximum of 150 mg every week, according to the individual patient response and tolerability. An effective maintenance dose is expected to be between 600 mg/day and 1,200 mg/day.
The maximum total maintenance dose is 1,200 mg/day. The safety and efficacy of doses higher than 1,200 mg/day have not been established.
If patients miss one dose or more, it is recommended that they take a single dose as soon as they remember.
After taking a missed dose, at least 3 hours should be allowed before the next dose and then the normal dosing schedule should be resumed.
When withdrawing Trobalt, the dose must be gradually reduced (see section 4.4).
Renal impairment
Retigabine and its metabolites are eliminated principally by renal excretion.
No dose adjustment is required in patients with mild renal impairment (creatinine clearance 50 to 80 ml/min; see section 5.2).
A 50% reduction in the initial and maintenance dose of Trobalt is recommended in patients with moderate or severe renal impairment (creatinine clearance <50 ml/min; see section 5.2). The total daily starting dose is 150 mg, and it is recommended that during the titration period, the total daily dose is increased by 50 mg every week, to a maximum total dose of 600 mg/day.
For patients with end-stage renal disease receiving haemodialysis, the three daily doses should be taken as usual on the dialysis day. In addition, a single supplemental dose is recommended immediately after haemodialysis. If breakthrough seizures occur towards the end of dialysis then an additional supplemental dose may be considered at the start of subsequent dialysis sessions.
Hepatic impairment
No dose reduction is required in patients with mild hepatic impairment (Child-Pugh score 5 to 6; see section 5.2).
A 50% reduction in the initial and maintenance dose of Trobalt is recommended in patients with moderate or severe hepatic impairment (Child-Pugh score ≥7; see section 5.2). The total daily starting dose is 150 mg, and it is recommended that during the titration period, the total daily dose is increased by 50 mg every week, to a maximum total dose of 600 mg/day.
Paediatric population
The safety and efficacy of retigabine in children below 18 years of age has not yet been established (see section 5.2).
Older people (65 years of age and above)
There are only limited data on the safety and efficacy of retigabine in patients aged 65 years and above. A reduction in the initial and maintenance dose of Trobalt is recommended in older patients. The total daily starting dose is 150 mg/day and during the titration period the total daily dose should be increased by a maximum of 150 mg every week, according to the individual patient response and tolerability. Doses greater than 900 mg/day are not recommended (see sections 4.4 and 5.2).
Method of administration
Trobalt must be taken orally in three divided doses each day. It may be taken with or without food (see section 5.2). The tablets should be swallowed whole, and not chewed, crushed or divided.
4.3 Contraindications
Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.
4.4 Special warnings and precautions for use
Eye disorders
Pigment changes (discolouration) of ocular tissues, including the retina have been reported in long-term clinical studies with Trobalt, sometimes but not always in conjunction with pigment changes of the skin, lips or nails (see below paragraph and section 4.8). The long-term prognosis of these findings is currently unknown, but some of the reports have been associated with visual impairment. A comprehensive ophthalmological examination (including visual acuity, slit-lamp examination, and dilated fundoscopy) should be performed at baseline and at least every 6 months thereafter while treatment is ongoing. If retinal pigment or vision changes are detected, treatment with Trobalt should only be continued after a careful re-assessment of the balance of benefits and risks. Trobalt should be discontinued unless no other suitable treatment options are available. If continued, the patient should be monitored more closely.
Skin disorders
Pigment changes (discolouration) of the skin, lips or nails have been reported in long-term clinical studies with Trobalt, sometimes but not always in conjunction with pigment changes of ocular tissues (see above paragraph and section 4.8). In patients who develop these changes, treatment with Trobalt should only be continued after a careful re-assessment of the balance of benefits and risks.
Urinary retention
Urinary retention, dysuria and urinary hesitation were reported in controlled clinical studies with retigabine, generally within the first 8 weeks of treatment (see section 4.8). Trobalt must be used with caution in patients at risk of urinary retention, and it is recommended that patients are advised about the risk of these possible effects.
QT interval
A study of cardiac conduction in healthy subjects has demonstrated that retigabine titrated to 1,200 mg/day produced a QT-prolonging effect. A mean increase in Individual Corrected QT Interval (QTcI) of up to 6.7 ms (upper bound of 95% one-sided CI 12.6 ms) was observed within 3 hours of dosing. Caution should be taken when Trobalt is prescribed with medicinal products known to increase QT interval and in patients with known prolonged QT interval, congestive cardiac failure, ventricular hypertrophy, hypokalaemia or hypomagnesaemia and in patients initiating treatment who are 65 years of age and above.
In these patients it is recommended that an electrocardiogram (ECG) is recorded before initiation of treatment with Trobalt and in those with a corrected QT interval >440ms at baseline, an ECG should be recorded on reaching the maintenance dose.
Psychiatric disorders
Confusional state, psychotic disorders and hallucinations were reported in controlled clinical studies with retigabine (see section 4.8). These effects generally occurred within the first 8 weeks of treatment, and frequently led to treatment withdrawal in affected patients. It is recommended that patients are advised about the risk of these possible effects.
Suicide risk
Suicidal ideation and behaviour have been reported in patients treated with antiepileptic agents in several indications. A meta-analysis of randomised placebo-controlled trials of antiepileptic drugs has also shown a small increased risk of suicidal ideation and behaviour. The mechanism of this risk is not known and the available data do not exclude the possibility of an increased risk for Trobalt.
Therefore patients should be monitored for signs of suicidal ideation and behaviours and appropriate treatment should be considered. Patients (and caregivers of patients) should be advised to seek medical advice if signs of suicidal ideation or behaviour emerge.
Older people (65 years of age and above)
Older patients may be at increased risk of central nervous system events, urinary retention and atrial fibrillation. Trobalt must be used with caution in this population and a reduced initial and maintenance dose is recommended (see sections 4.2 and 5.2).
Withdrawal seizures
As with other antiepileptic drugs, Trobalt must be withdrawn gradually to minimise the potential for rebound seizures. It is recommended that the Trobalt dose is reduced over a period of at least 3 weeks, unless safety concerns require an abrupt withdrawal.
4.5 Interaction with other medicinal products and other forms of interaction
Interaction studies have only been performed in adults.
Other antiepileptic drugs
In vitro data indicated a low potential for interaction with other antiepileptic drugs (see section 5.2). The drug interaction potential was therefore eva luated based on a pooled analysis across clinical studies and whilst not considered as robust as stand-alone clinical interaction studies, the results support the in vitro data.
Based on these pooled data, retigabine did not cause clinically significant effects on the plasma trough concentrations of the following antiepileptic drugs:
- carbamazepine, clobazam, clonazepam, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, phenobarbital, phenytoin, pregabalin, topiramate, valproate, zonisamide.
Further, based on pooled data, there were no clinically significant effects of the following antiepileptic drugs on retigabine pharmacokinetics:
- lamotrigine, levetiracetam, oxcarbazepine, topiramate, valproate.
This analysis also showed no clinically significant effect of the inducers (phenytoin, carbamazepine and phenobarbital) on retigabine clearance.
However, steady-state data from a limited number of patients in smaller phase II studies indicated that:
- phenytoin can reduce retigabine systemic exposure by 35%
- carbamazepine can reduce retigabine systemic exposure by 33%
Interaction with digoxin
Data from an in vitro study showed that the N-acetyl metabolite of retigabine (NAMR) inhibited P-glycoprotein-mediated transport of digoxin in a concentration-dependent manner.
Based on a study conducted in healthy volunteers, therapeutic doses of Trobalt (600-1,200 mg/day) resulted in a minor (8-18%) increase in digoxin AUC following a single oral dose of digoxin. The increase did not appear to be dependent on Trobalt dose and is not considered clinically relevant. There was no meaningful change in digoxin Cmax. No dose adjustment of digoxin is needed.
Interaction with anaesthetics
Trobalt may increase the duration of anesthesia induced by some anaesthetics (for example thiopental sodium; see section 5.1).
Interaction with alcohol
Co-administration of ethanol (1.0 g/kg) with retigabine (200 mg) resulted in an increase in visual blurring in healthy volunteers. It is recommended that patients are advised about the possible effects on vision if they take Trobalt with alcohol.
Laboratory tests
Retigabine has been shown to interfere with clinical laboratory assays of both serum and urine bilirubin, which can result in falsely elevated readings.
Oral contraceptives
At retigabine doses of up to 750 mg/day, there was no clinically significant effect of retigabine on the pharmacokinetics of the estrogen (ethinyl estradiol) or progestogen (norethindrone) components of the oral contraceptive pill. In addition, there was no clinically significant effect of the low dose combination oral contraceptive pill on the pharmacokinetics of retigabine.
4.6 Fertility, pregnancy and lactation
Pregnancy
Risk related to antiepileptic drugs in general
Specialist advice should be given to women who are of childbearing potential. The need for treatment with antiepileptic drugs should be reviewed when a woman is planning to become pregnant. In women being treated for epilepsy, sudden discontinuation of antiepileptic drug therapy should be avoided as this may lead to breakthrough seizures that could have serious consequences for the woman and the unborn child.
The risk of congenital malformations is increased by a factor of 2 to 3 in the offspring of mothers treated with antiepileptic drugs compared with the expected incidence in the general population of approximately 3%. The most frequently reported defects are cleft lip, cardiovascular malformations and neural tube defects. Therapy with multiple antiepileptic drugs is associated with a higher risk of congenital malformations than monotherapy and therefore monotherapy should be used whenever possible.
Risk related to Trobalt
There are no adequate data from the use of retigabine in pregnant women. Animal studies are insufficient with respect to reproductive toxicity because the plasma levels achieved in these studies were less than those reached in humans at recommended doses (see section 5.3). In a developmental study in rats whose mothers were treated with retigabine during pregnancy, there was a delay in auditory startle response development of the offspring (see section 5.3). The clinical significance of this finding is not known.
Trobalt is not recommended during pregnancy and in women of childbearing age, not using contraception.
Breastfeeding
It is unknown whether retigabine is excreted in human breast milk. Animal studies have shown excretion of retagabine and/or its metabolites in breast milk. A decision on whether to continue/discontinue breast-feeding or to continue/discontinue therapy with Trobalt should be made taking into account the benefit of breast-feeding to the child and the benefit of Trobalt therapy to the woman.
Fertility
There were no treatment-related effects of retigabine on fertility in animal studies. However, the plasma levels achieved in these studies were less than those reached in humans at recommended doses (see section 5.3).
The effect of retigabine on human fertility has not been established.
4.7 Effects on ability to drive and use machines
Adverse reactions such as dizziness, somnolence, diplopia and blurred vision were reported in controlled clinical studies, particularly during titration (see section 4.8). It is recommended that patients are advised about the risk of such adverse reactions at treatment initiation and following each titration step, and that they are advised not to drive or operate machinery until they have established how Trobalt affects them.
As there is individual variation in response to all antiepileptic drug therapy, it is recommended that prescribers discuss with patients the specific issues of epilepsy and driving.
4.8 Undesirable effects
In pooled safety data from three multicentre, randomised, double-blind, placebo-controlled studies, adverse reactions were generally mild to moderate in intensity, and were most commonly reported in the first 8 weeks of treatment. There was an apparent dose-relationship for dizziness, somnolence, confusional state, aphasia, coordination abnormal, tremor, balance disorder, memory impairment, gait disturbance, blurred vision and constipation.
Adverse reactions that were most frequently reported to lead to discontinuation were dizziness, somnolence, fatigue and confusional state.
The following convention has been used for the classification of adverse reactions:
Very common:  ≥1/10
Common:  ≥1/100 to <1/10
Uncommon:  ≥1/1,000 to <1/100
Rare:  ≥1/10,000 to <1/1,000
Very rare:  <1/10,000.
Within each frequency grouping, adverse reactions are presented in order of decreasing seriousness.

1 Data from older patients indicates that they may be more likely to experience certain central nervous system events.
Description of selected adverse reactions
Adverse reactions related to voiding dysfunction, including urinary retention, were reported in 5% of retigabine-treated patients in the pooled safety dataset (see section 4.4). The majority of events occurred in the first 8 weeks of treatment, and there was no apparent dose-relationship.
In retigabine-treated patients in the pooled dataset, confusional state was reported in 9% of patients, hallucinations in 2% of patients and psychotic disorders in 1% of patients (see section 4.4). The majority of adverse reactions occurred in the first 8 weeks of treatment, and there was an apparent dose-relationship for confusional state only.
Adverse event data from clinical trial subjects showed a rate of event of discolouration of the nails, lips, skin and/or mucosa per patient year of exposure of 3.6%. The cumulative incidences of an event at 1 year, 2 years, 3 years, 4 years and 5 years of exposure are approximately 1%, 1.8%, 4.4%, 10.2% and 16.7% respectively.
Approximately 30-40% of clinical trial subjects who were being treated with retigabine and underwent a skin and/or ophthalmological examination had findings of discolouration of nails, lips, skin and/or mucosa or non-retinal ocular pigmentation, and approximately 15-30% of clinical trial subjects who were being treated with retigabine and underwent an ophthalmological examination had retinal pigmentation findings.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via:
Ireland
HPRA Pharmacovigilance, Earlsfort Terrace, IRL - Dublin 2; Tel: +353 1 6764971; Fax: +353 1 6762517. Website: www.hpra.ie; E-mail:medsafety@hpra.ie.
United Kingdom
the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.
4.9 Overdose
Symptoms and signs
There is limited experience of overdose with retigabine.
Retigabine overdoses in excess of 2,500 mg/day were reported during clinical studies. In addition to adverse reactions seen at therapeutic doses, symptoms of retigabine overdose included agitation, aggressive behaviour and irritability. There were no reported sequelae.
In a study in volunteers, cardiac arrhythmia (cardiac arrest/asystole or ventricular tachycardia) occurred in two subjects within 3 hours of receiving a single 900 mg retigabine dose. The arrhythmias spontaneously resolved, and both volunteers recovered without sequelae.
Management
In the event of overdose, it is recommended that the patient is given appropriate supportive therapy as clinically indicated, including electrocardiogram (ECG) monitoring. Further management should be as recommended by the national poisons centre, where available.
Haemodialysis has been shown to reduce the plasma concentrations of retigabine and NAMR by approximately 50%.
5. Pharmacological properties
5.1 Pharmacodynamic properties
Pharmacotherapeutic group: antiepileptics, other antiepileptics, ATC code: N03AX21.
Mechanism of action
Potassium channels are one of the voltage-gated ion channels found in neuronal cells and are important determinants of neuronal activity. In vitro studies indicate that retigabine acts primarily through opening neuronal potassium channels (KCNQ2 [Kv7.2] and KCNQ3 [Kv7.3]). This stabilises the resting membrane potential and controls the sub-threshold electrical excitability in neurons, thus preventing the initiation of epileptiform action potential bursts. Mutations in the KCNQ channels underlie several human inheritable disorders, including epilepsy (KCNQ2 and 3). The mechanism of action of retigabine on potassium channels has been well documented, however other mechanisms by which retigabine may assert an antiepileptic effect have yet to be fully elucidated.
In a range of seizure models, retigabine increased the threshold for seizure induction produced by maximal electroshock, pentylenetetrazol, picrotoxin and N-methyl-D-aspartate (NMDA). Retigabine also displayed inhibitory properties in multiple kindling models, for example, in the fully kindled state and in some cases during the kindling development. In addition, retigabine was effective in preventing status epilepticus seizures in rodents with cobalt-induced epileptogenic lesions, and inhibiting tonic extensor seizures in genetically susceptible mice. The relevance of these models to human epilepsy, however, is not known.
Pharmacodynamic effects
In rats, retigabine increased the sleep time induced by thiopental sodium from approximately 4 min to 53 min, and the propofol-induced sleep time from approximately 8 min to 12 min. There was no effect on sleep time induced by halothane or methohexital sodium. Trobalt may increase the duration of anesthesia induced by some anaesthetics (for example thiopental sodium).
Clinical efficacy of adjunctive retigabine therapy in partial onset seizures
Three multicentre, randomized, double-blind, placebo-controlled studies in a total of 1239 adult patients have been conducted to assess the efficacy of retigabine as adjunctive therapy of partial onset seizures, with or without secondary generalisation. All patients enrolled were to have had seizures that were not adequately controlled with 1 to 3 concomitant antiepileptic drugs, and more than 75% of all patients were taking ≥2 concurrent antiepileptic drugs. Across all studies, patients had a mean duration of epilepsy of 22 years and a median baseline seizure frequency ranging from 8 to 12 per 28 days. Patients were randomized to placebo or retigabine at 600, 900 or 1,200 mg/day (see Table 1). During an 8-week baseline period, patients had to experience ≥4 partial onset seizures per 28 days. Patients could not be seizure-free for ≥21 days. The duration of the maintenance phase was 8 or 12 weeks.
The primary efficacy endpoints were:
- percentage change in the 28-day total partial seizure frequency from baseline to the double-blind phase (titration and maintenance phases combined) in all three studies
- responder rate (defined as the percentage of patients with a ≥50% reduction in 28-day total partial seizure frequency) from baseline to the maintenance phase (Studies 301 and 302 only).
Retigabine was effective in adjunctive treatment of adults with partial onset seizures in three clinical studies (Table 1). Retigabine was statistically significantly superior to placebo at 600 mg/day (one study), 900 mg/day (two studies) and 1,200 mg/day (two studies).
The studies were not designed to eva luate specific combinations of antiepileptic drugs. Consequently, the efficacy and safety of retigabine when taken concomitantly with antiepileptic drugs that were less commonly used as background treatment in the clinical studies, including levetiracetam, has not been definitely shown.
Table 1. Summary of percentage changes in 28-day total partial seizure frequency and responder rates