SPINRAZA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SPINRAZA (SPINRAZA).
SPINRAZA (nusinersen) is an antisense oligonucleotide that modifies splicing of pre-messenger RNA of the survival motor neuron 2 (SMN2) gene to increase production of full-length SMN protein, which is deficient in spinal muscular atrophy (SMA).
| Metabolism | Nusinersen is metabolized via exonuclease (3' and 5')-mediated hydrolysis and not by cytochrome P450 enzymes. |
| Excretion | Primarily metabolized via exonuclease-mediated hydrolysis; renal excretion of intact drug is negligible (<1%). No biliary or fecal elimination is documented. |
| Half-life | Terminal elimination half-life in cerebrospinal fluid (CSF) is 135–177 days; in plasma, it is 63–87 days. The long CSF half-life supports monthly intrathecal dosing. |
| Protein binding | Approximately 77–94% bound to plasma proteins (primarily albumin and, to a lesser extent, α1-acid glycoprotein). |
| Volume of Distribution | Volume of distribution in plasma is approximately 0.25 L/kg after intrathecal administration; this reflects limited distribution to peripheral tissues. The drug is primarily distributed within the CNS. |
| Bioavailability | Not applicable for systemic routes; designed for intrathecal administration. Bioavailability via other routes is negligible and not used clinically. |
| Onset of Action | Intrathecal administration: Clinical improvement in motor function may be observed as early as 2–4 months after initiation, though the onset is variable and may require up to 6 months. |
| Duration of Action | Sustained clinical effect with continued dosing; due to the long half-life, therapeutic SMN protein levels in spinal motor neurons are maintained with 4-month maintenance dosing intervals. Cessation may lead to gradual loss of benefit over months. |
Loading dose: 12 mg (5 mL) intrathecally on days 0, 14, 28, and 63. Maintenance dose: 12 mg (5 mL) intrathecally once every 4 months.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for renal impairment. Safety and efficacy not established in severe renal impairment. |
| Liver impairment | No dose adjustment required for hepatic impairment. Not studied in Child-Pugh classes B or C. |
| Pediatric use | Weight-based dosing not required. Use same dosing regimen as adults: 12 mg intrathecally on days 0, 14, 28, 63, then every 4 months. For infants, volume may be reduced to 2 mL (12 mg/mL concentration) to limit CSF volume displacement. |
| Geriatric use | No specific dose adjustment recommended. Limited data in patients aged ≥65 years; use with caution due to potential comorbidities and reduced physiological reserve. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SPINRAZA (SPINRAZA).
| Breastfeeding | No data on presence in human milk, effects on breastfed infant, or milk production. Consider developmental and health benefits of breastfeeding alongside maternal need for Spinraza. |
| Teratogenic Risk | No human data available; animal studies show no evidence of teratogenicity at doses up to 5.4 mg/kg in monkeys. Risk cannot be excluded; use only if benefit outweighs potential risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
Thrombocytopenia, including acute severe thrombocytopenia, and coagulation abnormalities have been observed after administration; risk of renal toxicity including fatal glomerulonephritis.
| Serious Effects |
["Hypersensitivity to nusinersen or any excipients","Patients with unstable thrombocytopenia or coagulopathy"]
| Precautions | ["Thrombocytopenia and coagulation abnormalities","Renal toxicity","Post-lumbar puncture syndrome including headache","Hydrocephalus","Serious infections including meningitis"] |
Loading safety data…
| No specific monitoring required; standard prenatal care. |
| Fertility Effects | No human data; animal studies in mice showed no adverse effects on male or female fertility at doses up to 3.7 mg/kg. |