Adult: Initially, 300 mg daily for 1 wk; thereafter, the total daily dose is adjusted by max wkly increments of 150 mg, according to response and tolerability, to a usual maintenance dose of 600-1,200 mg daily. Doses are to be given in 3 divided doses daily. Elderly: ≥65 yr Initially, 150 mg daily, followed by max wkly increments of 150 mg to a max maintenance of 900 mg daily.
Renal Impairment
CrCl (mL/min)
Dosage
<50
Initially, 150 mg daily, followed by max wkly increments of 50 mg to max of 600 mg daily.
Hepatic Impairment
Moderate to severe: Initially, 150 mg daily, followed by max wkly increments of 50 mg to max of 600 mg daily.
Administration
May be taken with or without food. Swallow whole, do not chew/crush.
Special Precautions
Patient w/ known QT interval prolongation, CHF, ventricular hypertrophy, hypokalaemia, hypomagnesaemia and those at risk of urinary retention. Avoid abrupt withdrawal. Moderate to severe hepatic or renal impairment (CrCl <50 mL/min). Elderly. Pregnancy and lactation.
Adverse Reactions
Dizziness, somnolence, fatigue, confusional state, aphasia, abnormal coordination, tremor, balance disorder, memory impairment, gait disturbance, blurred vision, constipation, anxiety, psychotic disorders, paraesthesia, wt gain, nausea, dyspepsia, urinary retention and hesitation, dysuria; discolouration of ocular tissues (including the retina), skin, lips, and nails; prolongation of QT interval.
Patient Counseling Information
This drug may cause dizziness, somnolence, diplopia and blurred vision, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor electrolytes and bilirubin levels, renal and hepatic function, urologic symptoms. Observe patient for excessive sedation, confusion, psychotic symptoms and hallucinations; suicidality; discolouration of skin, lips and nails. Perform ECG before starting therapy (in patients w/ risk factors for QT prolongation); baseline and periodic (6 mthly) ophthalmological exam.
Overdosage
Symptoms: Agitation, aggressive behaviour, irritability; cardiac arrhythmia (cardiac arrest/asystole or ventricular tachycardia) may occur. Management: Supportive treatment. Ensure an adequate airway, ventilation and oxygenation.
Drug Interactions
May prolong the effect of some anaesth (e.g. thiopental Na). Additive effects w/ drugs that prolong QT interval including class Ia/III antiarrhythmics (e.g. quinidine, amiodarone), some antipsychotic agents (e.g. chlorpromazine), and some antimicrobial agents (e.g. clarithromycin). Reduced plasma levels w/ phenytoin or carbamazepine.
Food Interaction
Increased incidence of blurred vision w/ alcohol.
Lab Interference
May falsely elevate serum and urine bilirubin assays.
Action
Description: Retigabine activates specific voltage-gated K channels in the brain known as the KCNQ (Kv7.2-7.5) family of ion channels, thereby stabilising the K channels in open formation, enhancing the M-type current and exerting a hyperpolarising effect on neuronal cells, resulting to stabilisation of the resting membrane potential and suppression of seizure activity. Pharmacokinetics: Absorption: Readily absorbed. Bioavailability: Approx 60%. Time to peak plasma concentration: Approx 0.5-2 hr. Distribution: Well distributed in the body. Volume of distribution: 2-3 L/kg. Plasma protein binding: Approx 80%. Metabolism: Extensively metabolised, mainly via glucuronidation by the uridine diphosphate glucuronosyltransferase 1A4 (UGT1A4) to form inactive N-glucuronides (major metabolites); also undergoes acetylation by N-acetyltransferase 2 (NAT2) to form an active, but less potent, N-acetyl metabolite (NAMR) that is subsequently glucuronidated. Excretion: Via urine, approx 85% (36% as unchanged drug, 18% as NAMR, and 24% as N-glucuronides); faeces (approx 14%, w/ 3% as unchanged drug). Elimination half-life: Approx 6-11 hr (retigabine and NAMR).
Chemical Structure
Retigabine Source: National Center for Biotechnology Information. PubChem Database. Retigabine, CID=121892, https://pubchem.ncbi.nlm.nih.gov/compound/Retigabine (accessed on Jan. 22, 2020)
N03AX21 - retigabine ; Belongs to the class of other antiepileptics.
References
Anon. Ezogabine . Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 01/04/2016.Buckingham R (ed). Retigabine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/04/2016.McEvoy GK, Snow EK, Miller J et al (eds). Ezogabine. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 01/04/2016.Potiga Tablet, Film Coated (GlaxoSmithKline LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 01/04/2016.
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