Amifampridine (Firdapse) is a potassium channel blocker primarily indicated for the treatment of Lambert-Eaton Myasthenic Syndrome (LEMS). 

Dosage and Administration of Amifampridine (Firdapse)

The following is detailed information regarding the dosage and administration of amifampridine.

1. Dosage Information

Table 1 outlines the recommended dosage regimens of amifampridine for adult patients and pediatric patients aged 6 years and older. The recommended dosage regimen for pediatric patients is determined by the patient's body weight. Dosage should be increased every 3-4 days based on clinical response and tolerability.

2. Patients with Renal Impairment

For patients with renal impairment, the recommended starting dose is the lowest recommended initial daily dose (i.e., 15 mg per day for pediatric patients weighing ≥ 45 kg and adult patients, and 5 mg per day for pediatric patients weighing < 45 kg), administered in divided oral doses. There is no recommended dosage of amifampridine for patients with end-stage renal disease.

3. Patients with Hepatic Impairment

For patients with hepatic impairment of any severity, the recommended starting dose of amifampridine is the lowest recommended initial daily dose (i.e., 15 mg per day for pediatric patients weighing ≥ 45 kg and adult patients, and 5 mg per day for pediatric patients weighing < 45 kg), administered in divided oral doses.

4. Patients with Known Poor N-Acetyltransferase 2 (NAT2) Metabolism

For patients with known poor N-acetyltransferase 2 (NAT2) metabolism, the recommended starting dose is the lowest recommended initial daily dose (i.e., 15 mg per day for pediatric patients weighing ≥ 45 kg and adult patients, and 5 mg per day for pediatric patients weighing < 45 kg), administered in divided oral doses.

5. Medication Instructions

Amifampridine can be taken on an empty stomach.

When a patient requires a dose of less than 5 mg/mL, has difficulty swallowing tablets, or needs a feeding tube, a 1 mg/mL suspension can be prepared (e.g., place the required number of tablets in a 50 to 100 mL container, add 10 mL of sterile water per tablet, wait for 5 minutes, then shake thoroughly for 30 seconds).

Tablets do not need to be crushed before preparing the suspension. After preparation, the correct dose of the suspension can be drawn up using an oral syringe and administered either orally or via a feeding tube.

Storage of the 1 mg/mL suspension: Refrigerate the suspension and shake it well before each administration. The suspension can be stored under refrigeration at 2°C to 8°C (36°F to 46°F) for up to 24 hours. Any unused portion of the suspension must be discarded after 24 hours.