Migraine Prevention Access: Same Drug, Same Results, Different Fine Print by Country

What drives a migraine

The decade's change in migraine care centers on one molecule: CGRP, calcitonin gene-related peptide, which plays a key role in generating migraine symptoms in the brain. CGRP-class drugs bind the molecule or its receptor and block the action.

Two definitions matter for everything below. Chronic migraine means 15 or more headache days a month, at least 8 of them migraine; episodic migraine means fewer than 15. These thresholds are not trivia. Most countries' reimbursement rules are built on exactly this line.

What does the evidence show

CGRP-targeted therapy is reported to nearly halve headache days in both episodic and chronic migraine, with the main side effects described as mild.

The decisive item for this article's comparison is a two-country dataset. When the Korean Headache Society compared treatment experience in Korea and Japan, response rates were the same, roughly 50 percent for episodic and 40 percent for chronic migraine, and adverse-event rates were similar. Efficacy and safety did not change at the border. Which leaves one question standing: what did change? That is the next section.

How do three countries gate the same drug

Country	Coverage condition	Coverage duration	Share of use actually covered	Level of evidence
United States	By society guidance, no fail-first requirement (2024); insurer practice varies	Varies by insurer	Not obtained	Practice (society guideline)
Japan	One failed drug, or chronic migraine	No limit	Not obtained	Practice (society account; original pending)
South Korea	Chronic migraine after 3+ drugs at maximum doses, 2 months each, 6 months total	Capped at one year	About 15 percent	Practice (society statements)

Table: reimbursement conditions for CGRP-targeted migraine prevention compared. This is a comparison of access, not efficacy.

United States: the society that dropped fail-first

The American story starts with approval dates. Two antibody drugs in this class received FDA approval in 2018, about two weeks apart, opening the global market.

Then, in 2024, came a document that shows the direction of travel. The American Headache Society, updating its position statement, placed CGRP-targeted therapies among first-line preventive options and stated that initiating them should not require trying and failing nonspecific preventive approaches. That reversed its own 2021 consensus, which had required trial and failure of two or more classes of standard preventives. The fail-first requirement, the same architecture on which Korea's reimbursement rule is built, is what the American society removed in 2024.

Society guidance and insurance practice are not the same thing, and this article does not cover US insurers' prior-authorization requirements or out-of-pocket costs, which were not verified this round. But the direction is unambiguous, and it frames the two sections that follow.

Japan: one failure opens the door

The same drug gets different treatment in Japan. By the Korean Headache Society president's account, Japanese insurance covers CGRP-targeted therapy for patients who have failed a single medication or who have chronic migraine, with no limit on duration. In the two-country comparison, efficacy and adverse events were alike; only the environment of use diverged sharply.

The door a Korean patient reaches after six months across three drugs, a Japanese patient opens with one failure. And where Korea's door closes after a year, Japan's stays open.

South Korea: coverage for one in six

The Korean section reduces to one number: 15 percent. By the Korean Headache Society, that is the share of this therapy's actual use that insurance covers. The conditions explain why. Coverage applies only to chronic migraine patients who have taken three or more medications at maximum doses, each for at least two months, six months in total, without adequate result, and even then coverage is limited to one year. In early 2024 the same society noted that only 10 percent of users were receiving coverage and said it would submit an opinion to the review agency.

The history gives the number its weight. The first drug in this class entered Korea's insurance formulary in 2022. The distance between "listed for coverage" in the headlines and actually being treated under coverage is, in Korea, five patients out of six. Meanwhile the regulator has also approved a once-daily oral CGRP receptor antagonist for migraine prevention: the options are widening while the door stays narrow.

Put the three countries in a row and the conclusion writes itself. Efficacy crosses borders; reimbursement criteria do not. One country is dismantling the fail-first gate, one asks for a single failure, and one still keeps five in six patients outside the door. The same patient, moved across a border, receives different medicine.

Period pain runs on the same split, with the treatment internationally uniform and the route to it anything but: one country sold daily contraceptives over the counter for decades while another approved its first in 2023, and a third bills the same pill differently depending on why you take it.

When does a headache need a doctor

Most headaches are primary, migraine or tension-type, where the headache is itself the condition. What clinicians must not miss is the minority of secondary headaches with another cause, and there is a list used in practice to screen for them. SNNOOP10, published in Neurology in 2019, includes: systemic symptoms including fever; a history of cancer; neurological deficit including reduced consciousness; sudden or abrupt onset; onset after age 65; a change in pattern or a new headache; positional headache; headache triggered by sneezing, coughing or exercise; papilledema (a finding checked in an examination, not at home); progressive headache with atypical features; pregnancy or the postpartum period; painful eye with autonomic features; post-traumatic onset; immune-system conditions such as HIV; and painkiller overuse or a new drug at headache onset.

The authors attached a caveat that must travel with the list: prospective epidemiological studies of red flags are lacking, many secondary headaches are rare, and many questions remain unanswered pending large prospective studies. It has also been noted that the mnemonic grew from expert opinion rather than a formally derived and validated screening tool. So the list shifts probabilities; it does not deliver verdicts. If an item applies to you, the correct use is to skip self-diagnosis and get examined. Red-flag lists behave the same way one condition over: a review of 16 national back pain guidelines found 46 distinct red flags, many of them appearing in only one country's document.

And short of an emergency, there is a line worth knowing: 15 or more headache days a month meets the definition of chronic migraine. That is not a stage to keep bridging with painkillers.

Frequently asked questions

Frequently asked

What changed in US migraine guidance in 2024?

The American Headache Society moved CGRP-targeted therapies into first-line preventive options and stated that starting them should not require first trying and failing nonspecific preventives, reversing its 2021 requirement of two failed drug classes. It is a statement about access architecture, not a comparison of drug efficacy.

If the drug is the same, why is access so different between Japan and Korea?

Because reimbursement rules, not molecules, decide who gets treated. The two-country comparison found the same response and safety profile, yet Japan covers after one failed drug with no time cap while Korea requires three failed drugs over six months and caps coverage at a year, with about 15 percent of use actually covered.

What is SNNOOP10?

A clinical checklist of red and orange flags for secondary headaches, 15 items spanning systemic symptoms, neurological signs, onset patterns and personal history. Its own authors note the evidence behind individual flags is thin and prospective studies are lacking, so it is a screening prompt for clinicians, not a self-diagnosis tool.

When is a headache itself the emergency?

Sudden or abrupt onset, accompanying neurological deficit or reduced consciousness, and fever with systemic signs are the kinds of features that move a headache up the urgency ladder in clinical screening. If any of these describes your headache, the answer is an examination now, not a search engine.