For most of the last century, every drug used to prevent migraine was borrowed from somewhere else — propranolol from cardiology, topiramate from epilepsy, amitriptyline from depression, even Botox from cosmetics. The CGRP monoclonal antibodies are different. They are the first class of medications designed specifically for migraine, targeting the actual molecule that drives the pain. In 2026, Australia has four such medications — three subsidised on the PBS, one private only.

This post explains what CGRP is, how these medications work, which four are available in Australia, who qualifies under the PBS, and what to expect from treatment.

What is CGRP and why does it matter?

CGRP — calcitonin gene-related peptide — is a small protein released from sensory nerve endings around the brain and its coverings (the meninges) during a migraine. It is the central chemical messenger that drives migraine pain. CGRP causes blood vessels to dilate, triggers neurogenic inflammation, and amplifies pain signals to the brain.

Decades of research established CGRP as a critical step in the migraine cascade. The CGRP monoclonal antibodies block this step. They are large protein molecules — antibodies — that either bind CGRP itself and inactivate it, or block the CGRP receptor on the nerve. Either way, the migraine signal is interrupted before it generates pain.

The four CGRP medications available in Australia

Each works on the same pathway, with subtle differences in target, dosing schedule and route. Three are PBS-subsidised. The fourth is registered for use in Australia but is not on the PBS, making it considerably more expensive.

1. Emgality (galcanezumab) — PBS-listed

The first CGRP monoclonal antibody PBS-listed in Australia (June 2021). Given by monthly subcutaneous self-injection using a pre-filled pen at home. A loading dose (double the usual dose) is given at the first injection. Onset of effect is typically within 4–8 weeks. Most patients tolerate it very well, with injection-site reactions the main side effect.

2. Ajovy (fremanezumab) — PBS-listed

Available as monthly or quarterly subcutaneous self-injection — the only CGRP mAb with the option of dosing only four times a year. Useful for patients who travel or who want fewer injections. Otherwise broadly similar to Emgality in efficacy and side-effect profile.

3. Vyepti (eptinezumab) — PBS-listed, IV

Different from the others — given as a 30-minute intravenous infusion every 3 months at a designated infusion centre. The IV route gives the fastest onset of any CGRP mAb — patients sometimes report benefit within days. Useful for patients who are needle-averse for self-injection, those who travel and want fewer treatment events, and where rapid response matters.

4. Aimovig (erenumab) — registered, NOT PBS-listed

The only CGRP medication that targets the CGRP receptor rather than CGRP itself. Given by monthly subcutaneous self-injection. It was actually one of the first CGRP mAbs developed but has never been PBS-listed in Australia. The full private cost (around $500 per month or more at pharmacy) puts it out of reach for most patients when three PBS-subsidised alternatives exist. I use it rarely in my practice for that reason. Constipation is somewhat more common with Aimovig than the other three — worth knowing in patients with baseline constipation.

Who qualifies under the PBS?

For the three PBS-listed agents (Emgality, Ajovy, Vyepti), the PBS criteria are essentially identical and require all of the following:

• Chronic migraine with at least 8 headache days per month, documented with a headache diary
• Failed adequate trials of at least 3 oral preventative medications from different classes — each at adequate dose and duration, discontinued for inefficacy or intolerance
• Prescribed by a neurologist
• Not concurrently on PBS-subsidised Botox for chronic migraine — you choose one or the other

Initial authority approval covers a treatment trial. Continuation requires demonstrated ≥50% reduction in headache days. This is a high bar that ensures the subsidy goes to clear responders.

What to expect from treatment

Once eligibility is established and the PBS authority approved, the practical journey is straightforward:

1. First dose — for self-injection medications (Emgality, Ajovy), this is usually given in the rooms with technique training. The pen device is straightforward and most patients are comfortable self-injecting at home from dose 2 onwards. For Vyepti, the first infusion is scheduled at an infusion centre.
2. Headache diary — continues throughout treatment. This is what we use to assess response at the formal review point.
3. Response timing — many responders notice benefit within 4–8 weeks. Vyepti’s onset can be faster (within days for some patients). PBS guidelines require 3 months of treatment before formally assessing response.
4. Response assessment — at 3 months and again at 6 months. Continuation requires ≥50% reduction in headache days from baseline.
5. Ongoing — once stable, follow-up is typically every 3–6 months for the duration of treatment.

Side effects

One of the genuine advantages of CGRP monoclonal antibodies over older preventatives is their excellent side-effect profile. Unlike topiramate (cognitive slowing, tingling, weight loss), amitriptyline (sedation, dry mouth, weight gain), or propranolol (fatigue, bronchospasm), CGRP mAbs have few systemic effects.

• Injection-site reactions (redness, mild soreness) — most common, usually mild
• Constipation — more common with Aimovig than the others
• Hypersensitivity reactions — rare
• Long half-life consideration — these medications remain in the system for months after the last dose

Pregnancy and breastfeeding

CGRP monoclonal antibodies are not recommended in pregnancy. Because they have long half-lives — several months — washout is required before planned conception. For most CGRP mAbs, the rule of thumb is to stop treatment at least 5 months before trying to conceive. If you are considering pregnancy, please raise this at consultation so we can plan the transition in advance.

CGRP or Botox?

Both CGRP monoclonal antibodies and Botox are now PBS-subsidised options for chronic migraine. Both work on the CGRP pathway — just at different points (Botox blocks release at the nerve terminal; CGRP mAbs neutralise circulating CGRP or block its receptor). Response rates are broadly similar. PBS rules permit only one at a time.

Practical factors guide the choice:

• Frequency and route — Botox is a 12-weekly in-rooms procedure (31 injections in 8 minutes); CGRP mAbs are monthly or quarterly self-injection (or quarterly infusion for Vyepti)
• Onset — CGRP mAbs often act within 4–8 weeks; Botox often takes until cycle 2 (24 weeks) to show full effect
• Medication overuse — Botox is often preferred where there is significant medication-overuse headache, as the dosing pattern helps break the cycle
• Self-injection preference — some patients prefer at-home self-injection (CGRP mAbs); others prefer an in-clinic procedure (Botox or Vyepti)
• Pregnancy plans — CGRP mAbs need a long washout before conception; Botox does not

For a detailed side-by-side comparison and the full clinical detail, see CGRP Therapies — Sydney Headache Centre and Botox for Chronic Migraine. The companion piece on the bespoke “follow the pain” Botox technique is here.

How to access

CGRP medications require a specialist (neurologist) prescription under the PBS. The path is:

1. GP referral to a neurologist
2. Headache diary documenting baseline frequency (longer is better — at minimum 1 month, ideally 3 or more)
3. List of previously trialled oral preventatives — name, dose, duration, reason for stopping
4. Specialist consultation to confirm eligibility, choose the right agent, and submit the PBS authority application
5. Pharmacy collection (for SC self-injection) or infusion booking (for Vyepti)

The bottom line

CGRP monoclonal antibodies have meaningfully changed the migraine treatment landscape. For patients with chronic migraine who have failed multiple oral preventatives, three PBS-subsidised options now exist alongside Botox. Each medication has its own niche — Emgality is the well-tested monthly default, Ajovy adds quarterly dosing flexibility, Vyepti offers IV administration and the fastest onset. Aimovig remains available privately but is rarely used in practice.

If you have chronic migraine and want to discuss whether a CGRP medication is right for you, please contact our Bondi Junction rooms or read the detailed treatment page at Sydney Headache Centre.

Related reading

• CGRP therapies overview — Sydney Headache Centre
• Chronic migraine Botox — PBS criteria and what to expect
• Migraine — types, triggers, and treatment
• Medication overuse headache
• Cluster headache
• Headache diary (online)

Dr Ron Granot is a consultant neurologist (FRACP) based in Bondi Junction, Sydney. He trained at Prince of Wales Hospital — Sydney’s leading headache neurology centre — and prescribes all three PBS-listed CGRP monoclonal antibodies for chronic migraine.