Pharmacologic class (EPC) · 3 drug pages

Potassium channel blocker: adverse event reports filed with FDA

64,845 reports list a drug in this class as a suspect or interacting product, 2010–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

64,845
reports across the class: 0.3% of all reports; 1,334
reports, 12 months to June 2026: 975 in the 12 months before; 26.9%
marked serious by the reporter: 57.4% across all reports; 3
drugs with a page: brand and generic names counted separately

Potassium channel blocker is a pharmacologic class (an FDA Established Pharmacologic Class) with 3 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 64,845 adverse event reports received by FDA, 0.3% of the database, from April 2010 to June 2026.

1,334 reports arrived in the 12 months to June 2026, up 37% from 975 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 26.9% of the class's reports are marked serious, 2.7% record death among the outcomes and 13.3% record hospitalisation, as reported.

Across the class the reactions recorded most often are gait disturbance (15.3%), drug ineffective (12.6%) and fall (10%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
AmpyraDalfampridine	brand	56,261	295	23%	Gait disturbance
Dalfampridine	generic	5,760	301	51.9%	Fall
FirdapseAmifampridine phosphate	brand	2,824	738	51.9%	Asthenia

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Gait disturbancedifficulty walking15.3%9,920
Drug ineffectivethe medicine did not work as expected12.6%8,187
Falla fall10%6,474
Therapy cessation7.5%4,879
Fatiguetiredness6.8%4,405
Balance disorderproblems with balance6.7%4,363
Condition aggravatedthe condition being treated got worse5.8%3,781
Multiple sclerosis relapsea flare of multiple sclerosis5.8%3,735
Dizzinesslight-headedness or unsteadiness5.7%3,710
Urinary tract infectionbladder or urinary infection4.9%3,168
Insomniadifficulty sleeping4.8%3,087
Astheniaweakness or lack of energy4.7%3,079
Headachehead pain4.4%2,828
Mobility decreasedreduced ability to move about4.1%2,686
Nauseafeeling sick3.9%2,513
Multiple sclerosis3.8%2,450
Muscular weaknessmuscle weakness3.7%2,407
Memory impairmentmemory problems3.1%1,986
Drug dose omissiona dose was missed3%1,930
Paraesthesiatingling or pins and needles2.8%1,803
Painpain, site not specified2.7%1,719
Hypoaesthesianumbness2.6%1,708
Flushingsudden reddening or warmth of the skin2.6%1,705
Back painback pain2.6%1,691
Inappropriate schedule of drug administrationthe medicine was taken at the wrong times2.6%1,663

Solid bar: share of all class reports. Hollow bar: the median share across the 3 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death2.7%1,764

Life-threatening0.3%192

Hospitalisation (initial or prolonged)13.3%8,636

Disability2.2%1,397

Congenital anomaly0%7

Other serious15.6%10,119

Not serious73.1%47,428

Patient age

Under 20%10

2 to 110%21

12 to 170%22

18 to 446.2%4,024

45 to 6425.5%16,539

65 to 748.2%5,322

75 and over1.8%1,196

Age not given58.2%37,711

Who reported

Physician5.3%3,464

Pharmacist5.8%3,784

Other health professional7.3%4,705

Lawyer0%1

Consumer or non-health professional75.1%48,722

Not given6.4%4,169

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about Potassium channel blocker reports

Which drugs are in the Potassium channel blocker class on this site?

Ampyra, Dalfampridine and Firdapse. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

64,845 reports through June 2026, 1,334 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

gait disturbance (15.3%), drug ineffective (12.6%), fall (10%), therapy cessation (7.5%) and fatigue (6.8%).

Can the members table be used to rank the drugs?

No. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. See the guide on how to report.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.