Side Effects of Ampyra (dalfampridine)

Ampyra (dalfampridine) is a potassium channel blocker used to treat multiple sclerosis (MS). Its exact mechanism of action is unknown, but it is known to block movement of potassium between nerve cells. In animal studies Ampyra increased the conduction of nerve signals.

Common side effects of Ampyra include

• urinary tract infections (UTIs),
• nausea,
• insomnia,
• dizziness,
• headache, and
• back pain.

Serious side effects of Ampyra include

• seizures and
• severe allergic reactions (anaphylaxis).

Symptoms of anaphylaxis include

• difficulty breathing;
• itching, and
• swelling of the throat or tongue.

Drug interactions have not been identified for Ampyra. 

There are no adequate studies of Ampyra in pregnant women. It is unknown if Ampyra is excreted in breast milk. Consult your doctor before breastfeeding.

The most common side effect of Ampyra is urinary tract infections.

Other common side effects include:

• nausea,
• insomnia,
• dizziness,
• headache, and
• back pain.

Serious side effects of Ampyra include:

• seizures, and
• severe allergic reactions (anaphylaxis).

People with a history of seizures should not use Ampyra.

Signs and symptoms of anaphylaxis include

• difficulty breathing;
• itching, and
• swelling of the throat or tongue.

The following serious adverse reactions are described in more detail elsewhere in the labeling:

• Seizures
• Anaphylaxis

Clinical Trials Experience

Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice.

In three placebo-controlled clinical trials of up to 14 weeks duration, 4% (15/400) of patients treated with Ampyra 10 mg twice daily experienced one or more adverse reactions leading to discontinuation, compared to 2% (5/238) of placebo-treated patients.

The adverse reactions leading to discontinuation of at least 2 patients treated with Ampyra and that led to discontinuation more frequently compared to placebo were

• headache (Ampyra 0.5%, placebo 0%),
• balance disorder (Ampyra 0.5%, placebo 0%),
• dizziness (Ampyra 0.5%, placebo 0%), and
• confusional state (Ampyra 0.3%, placebo 0%).

Table 1 lists adverse reactions that occurred in ≥2% of patients treated with Ampyra 10 mg twice daily, and more frequently than in placebo-treated patients, in controlled clinical trials.

Table 1: Adverse Reactions with an Incidence ≥2% of Ampyra-Treated Adult MS Patients and More Frequent with Ampyra Compared to Placebo in Controlled Clinical Trials

Other Adverse Reactions

• Ampyra has been evaluated in a total of 1,952 subjects, including 917 MS patients.
• A total of 741 patients have been treated with Ampyra for over six months, 501 for over one year and 352 for over two years.
• The experience in open-label clinical trials is consistent with the safety profile observed in the placebo-controlled clinical trials.
• As in controlled clinical trials, a dose-dependent increase in the incidence of seizures has been observed in open-label clinical trials with Ampyra in patients with MS as follows:
  • Ampyra 10 mg twice daily 0.41 per 100 person-years (95% confidence interval 0.13-0.96);
  • dalfampridine 15 mg twice daily 1.7 per 100 person-years (95% confidence interval 0.21-6.28).

Postmarketing Experience

The following adverse event has been identified during post-marketing experience with dalfampridine. Because adverse events are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure: vomiting.

OCT2 Inhibitors

• Concurrent treatment with OCT2 inhibitors, such as cimetidine, may cause increased exposure to dalfampridine.
• Elevated levels of dalfampridine increase the risk of seizures.
• The potential benefits of taking OCT2 inhibitors concurrently with Ampyra should be considered against the risk of seizures in these patients.

Baclofen

• No interaction was identified between dalfampridine and baclofen.