Botox vs CGRP Injections for Migraines: Key Differences

Both Botox and CGRP monoclonal antibodies are FDA-approved for chronic migraine prevention, and both cut monthly headache days in large placebo-controlled trials. They are not interchangeable. Botox (onabotulinumtoxinA) is injected into 31 specific head and neck muscle sites by a clinician every 12 weeks; CGRP monoclonal antibodies are monthly or quarterly self-injections targeting a single signaling molecule. Neither is clearly "better" for everyone — the choice depends on insurance coverage, whether you have already tried one option, how you feel about self-injecting at home, and how your body responds.

This explainer draws on peer-reviewed research from three leading headache specialists in the Convene directory: Peter Goadsby at UCLA, who co-discovered CGRP's role in migraine; Charles Argoff at Albany Medical Center, whose American Academy of Neurology reviews helped define the evidence standards for both treatments; and Richard Lipton at Montefiore, whose population research showed how many migraine patients qualify for prevention and how few actually receive it.

What is chronic migraine?

Migraine becomes classified as chronic when it crosses a threshold of 15 or more headache days per month, with at least 8 of those days carrying migraine features such as pulsing pain, nausea, or light sensitivity. This is a meaningful cutoff: people below it have episodic migraine, and only a subset of preventive treatments are approved specifically for the chronic form. About 2 to 3 percent of people with migraine have the chronic pattern at any given time, but because migraine is so common, that still translates to millions of Americans.

Lipton's 2007 study in Neurology documented how large this undertreated population is. Among people with migraine who meet standard criteria for preventive therapy, fewer than half ever receive it [7]. A separate paper from the same group introduced the Migraine Disability Assessment questionnaire, which quantifies how many days of school, work, or household activity are lost per month to migraine — a tool that now helps clinicians and patients decide when to escalate treatment [8]. Those numbers help explain why the arrival of Botox and then CGRP injections was such a significant development: they gave neurologists two new options with strong trial evidence to offer the large group of patients for whom older daily pills were not working or not tolerable.

How Botox works for migraine

OnabotulinumtoxinA, sold as Botox, was FDA-approved for chronic migraine in 2010 following the PREEMPT clinical program. The injections are given into 31 fixed sites across the forehead, temples, back of the head, neck, and upper shoulders — a protocol designed to cover the nerve endings most involved in triggering migraine. The mechanism is not the same as cosmetic Botox. In the migraine context, the toxin blocks the release of neuropeptides including CGRP and substance P from trigeminal nerve terminals. By reducing that chemical signaling, it raises the threshold for attacks rather than treating a headache already underway. Each treatment session takes about 15 to 20 minutes in a neurologist's office, and it is repeated every 12 weeks.

The PREEMPT trials showed that patients who received onabotulinumtoxinA had significantly fewer headache days per month than those who received placebo, and that benefit increased over successive treatment cycles. A 2008 evidence-based review of botulinum neurotoxin in pain conditions, published in Neurology and co-authored by Argoff, provided the early AAN-level framework for which patients were appropriate candidates and noted the accumulating evidence from headache trials [6]. The review highlighted that botulinum neurotoxin had demonstrated specific benefit in chronic daily headache and was mechanistically distinct from its use in other conditions — a distinction that mattered for insurance authorization.

One practical point: Botox for migraine is not something a patient does at home. Every treatment cycle requires a clinic visit. For patients who live far from a trained headache specialist, or who have limited time for appointments, that can be a real constraint.

How CGRP monoclonal antibodies work

CGRP stands for calcitonin gene-related peptide. In 1990, Goadsby and colleagues published a study in the Annals of Neurology measuring blood in the veins draining the head during a migraine attack. They found that CGRP levels spiked dramatically compared to levels between attacks — the first direct evidence that this peptide was actively released during migraine in humans [1]. That finding opened a new direction in migraine biology and, eventually, in drug development.

The proof-of-concept that blocking CGRP could stop a migraine came in a 2004 trial in the New England Journal of Medicine. Researchers used an early experimental CGRP receptor antagonist called BIBN 4096 BS given intravenously, and it worked: patients in the active arm had higher rates of headache relief at two hours compared to placebo [2]. The drug itself was never developed further, but the trial demonstrated that targeting CGRP was a viable therapeutic strategy.

What followed was the development of monoclonal antibodies — lab-made proteins that either bind to CGRP itself or to the receptor it activates, blocking the signal before it lands. The landmark trial of this approach was the STRIVE study of erenumab (Aimovig), published in the New England Journal of Medicine in 2017. STRIVE enrolled patients with episodic migraine averaging about 8 migraine days per month and randomized them to erenumab 70 mg, erenumab 140 mg, or placebo for six months. Both doses reduced monthly migraine days more than placebo, and roughly half of patients in the treatment arms had their migraine frequency cut in half or better [3]. Later trials confirmed similar results for fremanezumab (Ajovy), galcanezumab (Emgality), and eptinezumab (Vyepti) across both episodic and chronic migraine populations.

Three of the four approved CGRP antibodies are self-injected at home using a pen-style device, with a monthly or quarterly schedule. The injection goes into the skin of the abdomen or thigh, takes a few seconds, and most patients describe it as a brief sting.

Comparing the two options

The two treatments can also be used together. Some patients with chronic migraine who have a partial response to one or the other are offered both, though insurance coverage for combination therapy varies.

What the guidelines say

The American Academy of Neurology published evidence-based guidelines on pharmacologic prevention for episodic migraine in 2012, with Argoff as a co-author. The first of two companion papers reviewed oral medications including topiramate, valproate, and beta blockers, grading the evidence behind each [4]. The second covered NSAIDs, vitamins, and complementary treatments, establishing the hierarchy of evidence that neurologists still reference when deciding where to start [5].

Botox's inclusion in guidelines came through its own distinct evidence pathway, supported by the PREEMPT program and the AAN's evidence-based review of botulinum neurotoxin [6]. The key point the guidelines make is that preventive treatment in general is underused relative to how many patients qualify for it. Lipton's 2007 population data showed that the gap between who should receive prevention and who does is large [7]. Both Botox and CGRP injections have expanded the treatment menu, but access remains uneven, and most insurance payers require documented failure on one or more oral preventives before covering either injectable option.

Side effects and what to watch for

Botox side effects from the migraine protocol are generally localized and temporary. The most common are neck pain or stiffness at injection sites, and some patients notice eyelid drooping (ptosis) if the toxin spreads slightly near the eye. Flu-like muscle ache can occur in the first day or two after a session. Because the injections are given by a trained provider under a defined protocol, the risk of significant adverse events is low when the procedure is done correctly.

CGRP monoclonal antibodies have a clean side effect profile in the trial data. Injection-site reactions — redness, swelling, or brief stinging — are the most frequently reported complaint. Constipation has been noted in some patients, particularly with erenumab, and seems to be related to CGRP's role in gut motility. There is ongoing research into whether long-term CGRP blockade has any cardiovascular implications, since CGRP plays a role in dilating blood vessels, but no significant safety signals have emerged in post-market surveillance to date.

Neither treatment is recommended during pregnancy, and both should be discussed with a neurologist before use in patients with significant cardiovascular disease.

Who should consider switching or combining

For patients who have been on Botox for two or three treatment cycles and are still having 12 or more headache days per month, adding or switching to a CGRP monoclonal antibody is worth discussing with a neurologist. The reverse is also true: some patients who respond partially to a CGRP antibody have found additional benefit from adding Botox, particularly if their migraines are heavily concentrated in the neck and suboccipital region where Botox targeting is most direct.

Patients whose insurance currently covers only one option should ask their neurologist to document the treatment history carefully. Insurance authorization often depends on clear records of what was tried, for how long, and what the outcome was.

If you are still managing frequent migraines primarily with acute medications — triptans, NSAIDs, or over-the-counter pain relievers — and you have not been evaluated for preventive therapy, a headache specialist is the right next step. The MIDAS questionnaire gives a concrete picture of how much disability your migraines are causing [8], and that documentation can both inform the decision to start prevention and support insurance authorization.

Questions to ask your neurologist

• Do I have episodic or chronic migraine, and does that affect which treatment options are open to me?
• Have I tried enough oral preventives for my insurance to cover a CGRP injection or Botox?
• Am I a candidate for both Botox and a CGRP antibody, and is there evidence for combining them in my situation?
• If we start one of these treatments, how will we measure whether it is working, and what is the minimum response that would justify continuing?
• What do the out-of-pocket costs look like with my specific insurance plan, and are there manufacturer assistance programs that apply?
• Are there any features of my health history — cardiovascular disease, pregnancy plans, other medications — that favor one option over the other?

The bottom line

Botox and CGRP monoclonal antibodies are both proven chronic migraine preventives with real-world track records. Botox requires clinic visits every three months and is approved only for the chronic form; CGRP antibodies can be self-injected at home and work across episodic and chronic migraine alike. For most patients the practical question is not which treatment is theoretically superior but which one you can actually access, tolerate, and stick with. A headache specialist can work through that calculus with you — and if you have been relying primarily on pain medication to get through migraine days without ever discussing prevention, that conversation is overdue.