Fampridine

Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Fampyra (Biogen)
10 mg modified release tablets
Approved indication: multiple sclerosis
Australian Medicines Handbook section 16.6

Fampridine is a potassium channel blocker indicated for symptomatic improvement of walking in adults with multiple sclerosis, including relapsing remitting, secondary progressive, progressive relapsing and primary progressive. Currently there are no other drugs for this indication.

Fampridine is thought to increase conduction in demyelinated nerves by inhibiting potassium channels. It can be used on its own or with other treatments for multiple sclerosis, including immunomodulatory drugs.

The efficacy of fampridine has been studied in two phase III trials.^1,2 In the first trial, 301 patients with walking difficulties associated with multiple sclerosis were randomised to fampridine 10 mg twice daily or placebo, for 14 weeks. The primary outcome was based on changes in walking speed over 25 feet (7.6 m). A responder was defined as someone who consistently walked faster during treatment compared to baseline. In the fampridine group, 35% (78/224) of patients responded compared to only 8% (6/72) in the placebo group. The average increase in walking speed of people who responded to fampridine was 0.51 feet/second (approximately 15.5 cm/second) (25% faster).¹ These results were confirmed in a second similarly designed trial in which 43% (51/119) of patients responded to fampridine compared to only 9% (11/118) of patients to the placebo. On average, patients who responded to fampridine walked 24.7% faster.² Urinary tract infection was a very common adverse event with ampridine. Neurological effects were common and included insomnia, balance disorder, dizziness, headache and asthenia. Falls and severe anxiety were also reported. In a trial of 206 patients, serious events were more common at higher doses (4% with placebo, 0% with 10 mg, 8% with 15 mg and 12% with 20 mg fampridine). One patient discontinued the 15 mg dose of fampridine because of nausea and dizziness and five patients discontinued the 20 mg dose – two patients had seizures, one developed abnormal coordination, one had chest discomfort and headache and one patient had blurred vision, chest discomfort, balance disorder, headache and paraesthesia.³

Seizures have also occurred postmarketing and fampridine is contraindicated in patients with a history of seizures. Because of this potential toxicity, patients should not take a double or extra dose when a dose is missed. Tablets should be taken whole and not crushed or chewed.

Following oral administration, peak concentrations of fampridine are reached after 3–4 hours. It is primarily excreted unchanged in the urine. The elimination half-life is normally 5.2–6.5 hours, but is prolonged in patients with renal impairment. Fampridine is therefore contraindicated in moderate to severe renal impairment. If renal function has not been assessed, creatinine clearance should be estimated before starting treatment. This is particularly important in the elderly. In patients with mild impairment, monitoring of renal function should be considered.

This drug has not been tested in pregnant and lactating women. As fampridine is lipophilic, it may be excreted in human milk.

Fampridine is the first drug to help improve walking in patients with multiple sclerosis. However in the trials, less than half of the patients (35–43%) consistently walked faster (increase of 15.5 cm/second) after taking fampridine. Doctors and their patients have to consider whether this potential benefit is worth the risk of seizures and other serious neurological adverse effects. The safety and efficacy of fampridine during an exacerbation of multiple sclerosis is not known as these patients were excluded from the trials. Fampridine should only be continued if the patient responds within eight weeks of treatment.

manufacturer provided the product information

The Transparency Score () is explained in New drugs: transparency', Vol 37 No 1, Aust Prescr 2014;37:27.

Notes on references

At the time the comment was prepared, information about this drug was available on the web site of the Food and Drug Administration in the USA (www.fda.gov).

At the time the comment was prepared, a scientific discussion about this drug was available on the website of the European Medicines Agency (www.emea.europa.eu).