Sulthiame

Ospolot (international)

Antiseizure indications · UK product label

Indication / use

Label / evidence summary: No US antiseizure indication. In the UK, Ospolot 20 mg/mL oral suspension is indicated for Rolandic epilepsy (benign childhood epilepsy with centrotemporal spikes), now termed self-limited epilepsy with centrotemporal spikes (SeLECTS). The UK label is not U.S. approval.
Role: Maintenance · UK-labeled SeLECTS use
Class: Carbonic anhydrase inhibitor — sulfonamide

UK SmPC and patient-leaflet PDF checked 26 September 2026. The cited UK product is Ospolot 20 mg/mL oral suspension. Its indication and weight criteria do not establish U.S. approval or apply automatically to other formulations.

Ospolot 20 mg/mL oral suspension · UK UK label
Self-limited epilepsy with centrotemporal spikes (SeLECTS) · Children and adolescents weighing at least 12 kg; no numerical minimum age specified · Maintenance
UK label for Rolandic epilepsy / SeLECTS. Requires an experienced pediatric neurologist; weight must be at least 12 kg. The label notes limited controlled-trial evidence. No US antiseizure indication.

Formulations & strengths

International products; no U.S. FDA-approved label identified. Strengths are per unit or stated volume.

Oral suspension — UK

Strengths: 20 mg/mL
Product note: International product; shake 30 seconds.

Ospolot 20 mg/mL — UK SmPC, updated February 2026 ↗

Brand & formulation labels

Each link names the product and formulation it covers. Archived labels do not establish current availability.

Dosing & administration

Adult / product-specific schedule: The cited UK indication and dosing guidance concern pediatric Rolandic epilepsy / SeLECTS; no adult regimen is summarized.
Pediatric: UK SmPC: maintenance approximately 5–10 mg/kg/day, usually divided into three doses, for children and adolescents weighing at least 12 kg.
Titration / repeat dosing: UK SmPC: titrate individually over about one week; its starting-dose examples use 2.5 mg/kg/day. An experienced pediatric neurologist determines treatment duration and withdrawal; do not stop abruptly.
Dose basis: UK Ospolot oral-suspension SmPC; international labeling, not a U.S. indication.

Practical administration

Product instructions: UK oral suspension: 20 mg/mL. Shake well for at least 30 seconds, then draw up the dose immediately with the supplied oral syringe. See the product instructions for administration and feeding-tube use.

Ospolot 20 mg/mL oral suspension · UK SmPC (emc) ↗

Ospolot 20 mg/mL · UK patient leaflet (PDF) ↗

Dose adjustment & concentrations

Renal impairment: Caution: substantial urinary elimination; no validated renal dose table in the cited UK label. Closely monitor renal function and interacting phenytoin.
Hepatic impairment: Monitor liver enzymes; no validated hepatic dose algorithm in the cited UK label.
Serum reference information: No validated routine therapeutic range in the cited label. Use clinical response; monitor affected partner-drug levels when indicated.

Safety

Boxed warning: No U.S. boxed warning because no U.S. approved label was identified. International serious precautions still apply.
Contraindications: UK SmPC: hypersensitivity to sulthiame, other sulfonamides or excipients; hyperthyroidism; arterial hypertension; acute porphyria.
Serious precautions & monitoring: Monitor for metabolic acidosis, hyperventilation, paresthesias, renal stones, severe skin reactions and blood/liver/renal toxicity. The UK SmPC recommends CBC, liver enzymes and renal function before treatment, weekly for the first month, monthly for the first 6 months, then 2–4 times yearly. Stop for a persistent creatinine increase; severe hypersensitivity or symptomatic progressive thrombocytopenia/leukopenia also requires discontinuation. Exercise particular caution in renal impairment, psychiatric disease and Leber hereditary optic neuropathy.

Ospolot 20 mg/mL — UK SmPC, updated February 2026 ↗

Common / selected adverse effects

GI upset, nausea/vomiting
Paresthesias, dizziness, headache or diplopia
Reduced appetite and weight loss
Tachypnea/hyperpnea; consider acidosis
Mood/behavior changes

Ospolot 20 mg/mL — UK SmPC, updated February 2026 ↗

Drug interactions: toxicity & clinical action

Partner / combination	Clinical effect	Clinical action
Phenytoin	Can markedly increase phenytoin concentration/toxicity.	Frequent phenytoin monitoring, especially with renal impairment; adjust to levels and clinical signs.
Carbamazepine	May lower sulthiame concentration.	Monitor seizure control and adjust only under specialist supervision.
Lamotrigine / clobazam / other CYP2C19 substrates	Reported lamotrigine increases; active clobazam metabolite may rise.	Monitor concentration when useful and watch for rash, diplopia, ataxia or prolonged sedation.
Primidone / other carbonic anhydrase inhibitors	Primidone increases adverse-effect burden; topiramate/zonisamide/acetazolamide add acidosis/stone risk.	Review combinations; monitor bicarbonate, electrolytes and renal symptoms as indicated.
Alcohol	Potential disulfiram-like reaction and CNS effects.	Avoid alcohol per the UK SmPC.

Ospolot 20 mg/mL — UK SmPC, updated February 2026 ↗

Pregnancy & contraception

Fetal / neonatal risk: Human sulthiame pregnancy data are limited; animal embryotoxicity is reported. The UK SmPC does not recommend use during pregnancy.
Contraception: The UK SmPC also does not recommend sulthiame in people who could become pregnant and are not using contraception.
Pregnancy / postpartum monitoring: If treatment is necessary during pregnancy, the UK SmPC recommends the lowest seizure-controlling dose, preferably as monotherapy, and prenatal assessment for malformations.

UK SmPC — pregnancy and interactions ↗

Clinical evidence

Research summaries describe studied populations and outcomes; they do not add indications or constitute treatment recommendations.

Randomized controlled trial Guideline-supported off-label use

Trial summary

Primary endpoint: Six-month randomized placebo-controlled SeLECTS study (66 children, ages 3–11): treatment failure included a seizure after the 7-day run-in, intolerable adverse events, another epilepsy syndrome, or withdrawal requested by the family.
Results: No treatment-failure event: 25/31 (81%) with sulthiame versus 10/35 (29%) with placebo. This composite is not a pure seizure-freedom rate; this was not a U.S. registration trial.
Confidence intervals: A confidence interval is not reported in the PubMed abstract.
Discontinuations: No participant withdrew for adverse events in the published abstract; two placebo families requested withdrawal and four participants stopped for administrative reasons.
Exposure duration: Six months; sulthiame 5 mg/kg/day versus placebo in the published trial.
Seizure-frequency results: The UK SmPC states that controlled-trial evidence is limited and does not report a registration-style median seizure-frequency reduction.
Responder rate: No 50% responder rate is reported in the cited UK SmPC.
Seizure freedom: No seizure-freedom rate is reported in the cited UK SmPC; SeLECTS also has a high spontaneous-remission rate, so uncontrolled outcomes require caution.

Ospolot 20 mg/mL — UK SmPC, updated February 2026 ↗

Trial publications

PubMed · Controlled trial · SeLECTS (formerly BECTS) (2000) ↗

Comparative evidence

Findings: NICE places sulthiame after unsuccessful trials of lamotrigine and levetiracetam; this sequence is guideline positioning, not head-to-head evidence of superiority. The UK SmPC notes limited controlled-trial evidence and a high spontaneous-remission rate in SeLECTS.

Mechanism of action

Inhibits carbonic anhydrase; altered acid–base regulation is associated with reduced neuronal excitability. The complete clinical antiseizure mechanism is not established.
This is not a benzodiazepine or a direct GABA-A receptor modulator. Carbonic-anhydrase effects also explain acidosis and kidney-stone concerns.

Ospolot 20 mg/mL — UK SmPC, updated February 2026 ↗

Pharmacology

Adult values unless specified. Vd/F denotes apparent oral distribution volume.

Pharmacokinetics

Bioavailability: Rapid oral absorption; a reliable absolute bioavailability value is not provided in the UK SmPC or the cited human pilot study.
Elimination half-life: Approximately 12 hours after a single dose in healthy adults (UK SmPC); shorter values may occur in children. The small pilot study found nonlinear plasma/erythrocyte disposition.
Volume of distribution: Pilot adult model: apparent plasma compartment approximately 64.8 L, plus a saturable erythrocyte compartment of 3.3 L. These are model estimates from four volunteers, not validated pediatric dosing constants.
Active metabolite(s): No clinically established active metabolite contribution reported in the cited sources.
Active-metabolite half-life: Not established in the cited human/product sources.
Protein binding: Approximately 29% in the UK SmPC.
Metabolism / elimination: Approximately 32% excreted unchanged in urine within 24 hours; urinary and fecal elimination contribute.

International drug: pharmacokinetic evidence remains limited; do not assume linear kinetics or equate plasma and whole-blood concentrations.

Molecular structure

Principal compound; salt and product forms may differ.
NIH PubChem structure and record ↗

Product history

Initial U.S. approval: No US antiseizure indication or FDA-approved sulthiame product identified as of 26 September 2026.
Market / formulation history: Ospolot oral suspension: UK; film-coated tablets: Australia and other markets. Access is jurisdiction-specific.
Brands: Ospolot (international)
Manufacturer / marketer: Desitin (UK suspension); Phebra (Australian tablets)
Generic availability: Country-dependent; no U.S. approved generic identified.
Related drugs: See mechanism and syndrome guidance.

Sources & review status

UK SmPC and patient-leaflet PDF checked: 2026-09-26. Other profile sources reviewed: 2026-09-15 · label revision noted at that review: See linked product label. This is a draft reference; final review is pending.