When Will Gefapixant Be Available?

Gefapixant is already available by prescription in Japan and Switzerland, where it was approved for refractory or unexplained chronic cough, but it has not been approved in the United States, the European Union, or Canada. The U.S. Food and Drug Administration, the European Medicines Agency, and Health Canada have all been weighing the drug for several years without granting marketing authorization, largely because of concerns about a very common side effect: altered taste. For the millions of people living with a chronic cough that nothing else has helped, the wait has been frustrating, and the timeline remains uncertain.

Where Gefapixant Is Already on the Market

Japan became the first country to approve gefapixant, granting marketing authorization under the brand name Lyfnua in early 2022. The approval covered adult patients whose chronic cough had not responded to other treatments or had no identifiable underlying cause. Switzerland followed with its own approval shortly after. In both countries, the drug is prescribed at a dose of 45 mg taken twice daily.¹

These approvals were based on the same large phase 3 trials, known as COUGH-1 and COUGH-2, that have been submitted to regulators elsewhere. The fact that Japan moved first reflects differences in how national regulatory agencies weigh efficacy against side effects, and in how much unmet medical need factors into the approval decision. Japan has a sizable population of patients with unexplained chronic cough and relatively few approved treatment options, which likely influenced the faster green light.

Why the FDA Has Not Approved It

The FDA has not publicly issued a formal rejection of gefapixant, but the drug’s regulatory path in the U.S. has been notably slow. The core issue is the balance between how well the drug works and how often it causes taste-related problems. In the phase 3 trials, taste disturbance was reported frequently enough, and was bothersome enough, that regulators appear to have struggled with whether the cough reduction justifies the trade-off.

Merck (known as MSD outside the U.S.), which developed gefapixant, submitted a New Drug Application to the FDA. The agency issued a Complete Response Letter, which essentially means it did not approve the drug in its current application and requested additional information or actions. Complete Response Letters do not always end a drug’s chances. Companies often address the FDA’s concerns and resubmit. But each cycle of questions and responses adds months or years to the timeline, and Merck has not publicly committed to a firm resubmission date.

A systematic review published in JAMA confirmed that as of its writing, Japan and Switzerland had licensed gefapixant while the FDA, EMA, Health Canada, and other major regulatory authorities were still deliberating.²

What the Clinical Trials Actually Showed

The two pivotal trials, COUGH-1 and COUGH-2, enrolled patients with refractory chronic cough (cough persisting despite treatment of any identified causes) or unexplained chronic cough (no identifiable cause found after a thorough workup). Patients were randomly assigned to receive gefapixant at 15 mg twice daily, 45 mg twice daily, or a placebo.

At the higher dose, gefapixant reduced 24-hour cough frequency by about 18.5% more than placebo at 12 weeks in COUGH-1, and by about 14.6% more than placebo at 24 weeks in COUGH-2. Both results were statistically significant. The lower 15 mg dose, however, did not produce a significant reduction in cough frequency compared with placebo in either trial.³

Those numbers deserve some context. A roughly 15-to-19 percent reduction in cough frequency over placebo is meaningful for someone who coughs dozens or hundreds of times per day, but it is not a dramatic suppression. For comparison, many patients and clinicians hoped for larger effect sizes from a first-in-class mechanism. That modest efficacy, set against the high rate of side effects, is a significant part of why regulators outside Japan have hesitated. A drug that cuts coughing by a fifth but causes an unpleasant taste change in half of patients faces a harder approval calculus than one that halves coughing with mild side effects.

The Taste Problem

Gefapixant works by blocking a receptor called P2X3, which sits on sensory nerves involved in the cough reflex. The trouble is that gefapixant is not perfectly selective for the P2X3 receptor alone. It also blocks a closely related receptor, P2X2/3, which plays a role in how you perceive taste. When that receptor gets blocked in taste buds, people experience anything from a metallic or bitter taste to a reduced ability to taste food at all.

A meta-analysis of randomized trials found that about half of patients taking gefapixant experienced some form of taste disturbance, compared with only around 8% among patients taking newer, more selective P2X3 antagonists that spare the taste-related receptor.⁴ The dose-response meta-analysis published in JAMA similarly found a dose-dependent increase in the risk for taste-related side effects tied to gefapixant’s unselective blocking of both P2X3 and P2X2/3 receptors.⁵

For many patients, the taste change was enough to make them stop taking the drug during trials. This is a real problem for a medication intended for long-term use. People with chronic cough often deal with their symptoms for years; asking them to trade persistent coughing for persistent taste distortion is a hard sell. Some patients in clinical practice have found the trade-off worthwhile, particularly those whose cough was severe enough to interfere with sleep, work, and social life. But the high dropout rate from taste issues weakened the overall case for approval in some regulators’ eyes.

What Living with Refractory Chronic Cough Is Like

The reason there is so much interest in gefapixant despite its drawbacks is that refractory chronic cough is genuinely debilitating and has almost no approved treatments. A qualitative study examining the burden of the condition found that chronic cough affects nearly every aspect of daily life, from physical movement and concentration to sleep, meals, work, relationships, hobbies, and finances. Patients also reported a heavy emotional toll and the burden of repeated hospital visits searching for answers.⁶

Chronic cough that persists for more than eight weeks and does not respond to treatment of common causes like asthma, acid reflux, or postnasal drip gets labeled “refractory” or, if no cause is found, “unexplained.” Estimates vary, but it likely affects several percent of the adult population, with a higher prevalence among women and people in middle age and beyond. Many patients describe being dismissed by doctors who run out of things to try, and the social isolation from coughing constantly in public can be profound. This is the population gefapixant was designed to serve, and their lack of alternatives is why even a modestly effective drug with real side effects generates intense interest.

What Patients Are Using in the Meantime

Without gefapixant on the market in most countries, people with refractory chronic cough rely on a patchwork of off-label treatments. Speech-language pathology and specialized cough-suppression therapy, which teach patients techniques to control the urge to cough, have some evidence behind them. On the medication side, several neuromodulators originally developed for other conditions have shown benefit. A review of randomized trials and other studies found that amitriptyline, gabapentin, pregabalin, and baclofen all reduced cough severity or improved cough-specific quality of life in patients with chronic idiopathic cough.⁷

These medications work by dampening nerve signaling, and they can help, but they also come with their own side effects like drowsiness, dizziness, and weight gain. They are not approved specifically for chronic cough in most countries, meaning their use relies on individual clinician judgment. Low-dose morphine has also been studied and shows cough reduction, but the obvious concerns about opioid use make it a last resort. The bottom line is that treatment for refractory chronic cough before gefapixant-class drugs existed was improvised, and largely remains so outside Japan and Switzerland.

Competitors That May Arrive Sooner, or Instead

Gefapixant’s taste problem has motivated the development of more selective P2X3 receptor blockers that do not interfere with taste perception. The idea is straightforward: if you can block P2X3 without also blocking P2X2/3, you should keep the cough-suppressing effect while sparing the taste buds. Several pharmaceutical companies have pursued this approach.

One of the furthest along was eliapixant, developed by Bayer. In a phase 2b trial called PAGANINI, eliapixant showed efficacy in refractory chronic cough with a much better taste-side-effect profile than gefapixant. But the program was shut down entirely, across all indications, after cases of drug-induced liver injury emerged. The liver signal led to intensified monitoring and ultimately the decision to discontinue development.⁸

Other selective P2X3 antagonists remain in development from companies including Shionogi and Bellus Health (now acquired by GSK). Sivopixant, from Shionogi, has advanced through early clinical trials. BLU-5937 (camlipixant), from the Bellus/GSK pipeline, showed promising phase 2 results with lower rates of taste disturbance and moved into phase 3 trials. If any of these more selective drugs succeed, they could reach the market with a cleaner side-effect profile than gefapixant, potentially leapfrogging it in countries where it has not yet been approved.

This competitive landscape may actually affect gefapixant’s own path. If the FDA believes a better-tolerated drug is close behind, it faces less pressure to approve a first-in-class drug with known tolerability issues. On the other hand, if the newer competitors hit snags similar to eliapixant’s liver problems, gefapixant’s existing data set becomes more valuable again. The chronic cough treatment pipeline is genuinely uncertain.

How Cough Trials Measure Success

One underappreciated aspect of the gefapixant story is the technology used to measure whether the drug is working. Unlike many conditions where you can draw blood or take an image, cough is counted. Patients in the gefapixant trials wore ambulatory cough monitors that recorded sounds over 24 hours, and algorithms identified and tallied each cough. This approach, measuring 24-hour cough frequency, has become the gold standard primary endpoint for chronic cough clinical trials. It has also been used in other settings, like tracking infectiousness in tuberculosis and monitoring recovery from flare-ups of chronic lung disease.⁹

This matters because cough frequency and how much a cough bothers someone are not always the same thing. A patient might cough 15% less but feel dramatically better if the coughs that disappeared were the ones that woke them at night. Or they might cough 15% less and barely notice a difference. The phase 3 trials measured both cough frequency and patient-reported quality-of-life outcomes, and the drug performed somewhat differently on each. Regulators care about both, and the gap between a statistically significant frequency reduction and a clinically meaningful quality-of-life improvement is part of the approval debate.

What You Can Do If You Are Waiting

If you live outside Japan or Switzerland and have refractory chronic cough, your options are limited but not zero. The neuromodulators mentioned earlier, particularly gabapentin, have the most evidence and are commonly prescribed off-label by cough specialists. Speech therapy programs that focus on cough suppression techniques have shown real benefits in controlled trials, and some patients find them more helpful than medication. If you have not seen a specialist in chronic cough specifically, rather than a general pulmonologist or allergist, that is worth pursuing, since these specialists are more likely to be up to date on the latest off-label treatments and clinical trial opportunities.

Some patients have explored medical tourism to obtain gefapixant from Japan, though this involves obvious hurdles around cost, language, prescribing regulations, and follow-up care. Online patient communities for chronic cough sometimes discuss this route, but it is not straightforward and carries its own risks. If you are interested in the newer P2X3 antagonists, searching clinical trial registries for active or recruiting studies in your region is the most practical step. Phase 3 trials for competing drugs are ongoing, and enrollment typically provides the drug at no cost with close medical monitoring.

The honest answer to “when will gefapixant be available” in the U.S. or Europe is that nobody outside Merck and the regulatory agencies knows with confidence. The drug has not been withdrawn from consideration, but the path forward depends on whether Merck can address the FDA’s and EMA’s concerns, likely related to the benefit-risk balance given the taste disturbance rate. That could mean additional data, a more restricted indication, stronger risk-management plans, or simply waiting for the regulatory process to run its course. If a more selective competitor clears phase 3 trials with better tolerability, the commercial case for gefapixant in the remaining markets weakens further, but for patients with severe chronic cough who have exhausted every other option, even a drug with imperfect tolerability would be welcome.