SMN2 Splicing Modifier (Spinal Muscular Atrophy — Oral) Pregnancy: Not recommended during pregnancy or in women of childbearing potential not using contraception — there are no data in pregnant women and animal studies have shown reproductive toxicity. Pregnancy status should be verified before starting. Female patients of childbearing potential should use highly effective contraception during treatment and for at least 1 month after the last dose; male patients and their female partners of childbearing potential should both use highly effective contraception during treatment and for at least 4 months after the last dose. It is recommended not to breastfeed during treatment. Male fertility may be compromised during treatment (§4.6).

Risdiplam

Brand names: Evrysdi

Risdiplam is an orally administered SMN2 splicing modifier used to treat spinal muscular atrophy (SMA), a hereditary neuromuscular disorder caused by deficiency of survival motor neuron (SMN) protein.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 5 mg once daily (the dose for patients aged 2 years and over weighing 20 kg or more, which covers adults)

Route: Oral — powder for oral solution, taken using the re-usable oral syringe provided; an alternative film-coated tablet form is available for patients aged 2 years and over weighing 20 kg or more

Frequency: Once daily, with or without food, at approximately the same time each day

Max: Treatment with a daily dose above 5 mg has not been studied

Treatment should be initiated by a physician with experience in the management of SMA. The powder for oral solution must be constituted by a healthcare professional (e.g. pharmacist) before being dispensed. Do not mix with milk or formula milk; take immediately after drawing it up into the oral syringe and discard if not taken within 5 minutes; drink water afterwards to ensure the dose has been completely swallowed. The powder for oral solution may be given via a nasogastric or gastrostomy tube (flush the tube with water afterwards), but the tablet or tablet mixture must not be given via an NG or G-tube. Missed dose: administer as soon as possible if still within 6 hours of the scheduled dose, otherwise skip it and give the next dose at the regularly scheduled time the next day; do not give a replacement dose if a dose is not fully swallowed or vomiting occurs. No dose adjustment is required in the elderly, or in mild or moderate hepatic impairment; patients with severe hepatic impairment have not been studied and may have increased exposure. Dose volume should be rounded to the nearest graduation mark on the selected oral syringe (1 mL syringe for 0.3-1 mL, 6 mL syringe for 1-6 mL, 12 mL syringe for 6.2-6.6 mL).

Paediatric dose

Route: Oral (powder for oral solution; may be given via nasogastric or gastrostomy tube)

Frequency: Once daily, with or without food, at approximately the same time each day

Max: Treatment with a daily dose above 5 mg has not been studied

The recommended once-daily dose is determined by age and body weight, so no single per-kg figure applies and dosePerKg is left null: under 2 months of age 0.15 mg/kg; 2 months to under 2 years of age 0.20 mg/kg; 2 years of age and over weighing under 20 kg 0.25 mg/kg; 2 years of age and over weighing 20 kg or more, a flat 5 mg. Ages are based on corrected age for preterm infants. Use for SMA in patients 2 months of age and younger is supported by pharmacokinetic and safety data from paediatric patients 16 days and older; no pharmacokinetic data are available in patients less than 16 days of age.

Dose adjustments

Renal

Risdiplam has not been studied in renal impairment; no dose adjustment is expected to be required (§4.2)

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients (§4.3)

Side effects

Pyrexia including hyperpyrexia — 54.8% in infantile-onset SMA and 21.7% in later-onset SMA (very common)
Rash — 29.0% in infantile-onset and 16.7% in later-onset SMA (very common)
Diarrhoea — 19.4% in infantile-onset and 16.7% in later-onset SMA (very common)
Headache — 20.0% in later-onset SMA (very common)
Mouth ulcerations and aphthous ulcers, nausea (later-onset), arthralgia (later-onset), urinary tract infection including cystitis — common
Cutaneous vasculitis reported post-marketing

Interactions

Avoid co-administration with substrates of the multidrug and toxin extrusion transporters MATE1 or MATE2-K (e.g. metformin), as risdiplam may increase their plasma concentrations; if co-administration cannot be avoided, monitor for drug-related toxicities and consider reducing the dose of the co-administered drug (US EVRYSDI label §7; the UK SPC §4.5 was not retrieved in this bundle)

Clinical monograph

How it works

It modifies splicing of the SMN2 gene transcript to promote inclusion of exon 7, increasing production of functional, full-length SMN protein and thereby supporting motor neuron survival.

Prescribing in practice

Because it is potentially teratogenic and may affect fertility, appropriate contraceptive and reproductive counselling is required for those of childbearing potential.
It is a daily oral medicine that should be taken consistently, and care is needed with co-administration of drugs that are substrates of certain transporters owing to potential interactions.
Prescribe within specialist neuromuscular services according to the SPC and a children's formulary, including measures to ensure accurate administration of the oral solution.

Monitoring

Monitor motor function and treatment response within a specialist service; specific reproductive-safety counselling is required for those of childbearing potential.

Counselling the patient

Explain that the medicine is taken by mouth every day at around the same time and aims to improve or preserve muscle function.
Use the device provided to measure the dose accurately and follow instructions on handling the oral solution.
Discuss contraception and pregnancy planning with the specialist team before and during treatment.

Evidence & guidelines

Risdiplam is approved for SMA on the basis of the FIREFISH and SUNFISH trials, which showed improvements in motor milestones and function across infantile- and later-onset disease, and it is available in the UK through specialist commissioning.

Reference: Mercuri et al. NEJM 2022 (SUNFISH); NICE TA700; MHRA SPC Evrysdi; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways