RUZURGI
Clinical safety rating: caution
Comprehensive clinical and safety monograph for RUZURGI (RUZURGI).
Amifampridine blocks voltage-gated potassium channels, thereby prolonging the action potential duration and increasing calcium influx at the nerve terminal. This enhances acetylcholine release at the neuromuscular junction, improving muscle strength.
| Metabolism | Primarily metabolized by N-acetyltransferase 2 (NAT2) to N-acetylamifampridine. Polymorphisms in NAT2 may affect drug exposure. |
| Excretion | Primarily renal excretion of unchanged drug (~60%) with minor fecal elimination (~30%); <10% metabolized. |
| Half-life | Terminal elimination half-life is approximately 4.5 hours (range 3.5–5.5 h), supporting twice-daily dosing. |
| Protein binding | Approximately 85% bound to serum albumin. |
| Volume of Distribution | Volume of distribution is about 0.8 L/kg, indicating distribution into total body water. |
| Bioavailability | Oral bioavailability is approximately 70%. |
| Onset of Action | Oral: Onset within 30–60 minutes post-dose; peak plasma concentration at 1–2 hours. |
| Duration of Action | Duration of clinical effect is approximately 8–12 hours, consistent with dosing every 12 hours. |
32 mg orally three times daily (total daily dose 96 mg), to be taken with food.
| Dosage form | TABLET |
| Renal impairment | For GFR 30-59 mL/min: 32 mg twice daily. For GFR 15-29 mL/min: 32 mg once daily. For GFR <15 mL/min or on dialysis: not recommended. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: 16 mg twice daily. Child-Pugh Class C: not recommended. |
| Pediatric use | Safety and efficacy not established in pediatric patients. |
| Geriatric use | No specific dose adjustment recommended; monitor renal function and adjust based on GFR as per adult renal guidelines. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for RUZURGI (RUZURGI).
| Breastfeeding | Not recommended. Unknown if excreted in human milk; M/P ratio not established. Consider alternative treatments due to potential for serious adverse reactions in nursing infants. |
| Teratogenic Risk | Pregnancy Category C. First trimester: increased risk of major congenital malformations based on animal studies (cleft palate, skeletal defects). Second/third trimester: risk of fetal growth restriction and neurobehavioral effects. Avoid unless benefit outweighs risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Concurrent use of amifampridine with other potassium channel blockers such as 4-aminopyridine (4-AP)"]
| Precautions | ["Seizures: increased risk in patients with prior seizure history or conditions predisposing to seizures","Hypersensitivity reactions including anaphylaxis","Fetal harm: based on animal data, advise females of reproductive potential of potential risk"] |
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| Monitor maternal blood pressure and heart rate regularly. Fetal ultrasound for growth and anatomy. Consider nonstress test and biophysical profile in third trimester. Monitor for signs of placental insufficiency. |
| Fertility Effects | Animal studies show impaired fertility in females (reduced conception rates) at clinically relevant doses. Human data lacking; may cause menstrual irregularities. Males: possible reduced sperm motility and count. |