Botox Administration Frequency for Chronic Migraine
Botox (onabotulinumtoxinA) should be administered every 12 weeks (every 3 months) for chronic migraine prophylaxis. 1
Standard Treatment Protocol
The established treatment interval is every 12 weeks, which represents the evidence-based dosing schedule validated in the pivotal PREEMPT trials and endorsed by multiple guideline societies including the VA/DoD and European Headache Federation 1
Each treatment session involves administering 155-195 units across 31-39 injection sites following the PREEMPT protocol, which is the only evidence-based injection pattern for chronic migraine 1
Retreatment should be administered no more frequently than every three months to maintain safety and efficacy 2
Duration of Effectiveness
The maximum therapeutic effect typically occurs during the second month after injection, with effectiveness beginning to wane in the third month 3
In a real-world study, headache days decreased from baseline (18.95 days/month) to 10.55 days in month one, reached optimal reduction at 9.31 days in month two, then increased to 11.97 days by month three 3
Analgesic medication use similarly decreased most significantly in the second month (5.40 tablets/month) compared to the first month (6.53 tablets/month), with a slight increase by the third month (5.85 tablets/month) 3
Treatment Response Timeline
Patients require at least 2-3 treatment cycles (6-9 months) before being classified as non-responders, as therapeutic benefit often accumulates with repeated treatments 1
Long-term treatment studies demonstrate sustained efficacy over multiple injection series, with 96% of patients reporting benefit after an average of 6.5 injection series over 73 weeks 4
The reduction in migraine days becomes more pronounced with higher doses (195 U) after the third injection compared to lower doses (155 U), suggesting dose-dependent efficacy with repeated treatments 5
Critical Timing Considerations
Do not administer treatments more frequently than every 12 weeks, as this represents the studied and approved interval with established safety data 1, 2
If a patient's last injection was 6 months prior (26 weeks), they have exceeded the standard 12-week interval and should receive treatment promptly 1
Reconstituted Botox must be used within 24 hours and stored refrigerated at 2-8°C during this period; it is for single-dose, single-patient use only 2
Efficacy Evidence
The PREEMPT 2 trial demonstrated that onabotulinumtoxinA reduced headache days by 9.0 days compared to 6.7 days with placebo (p<0.001) when administered every 12 weeks for two treatment cycles 6
High-quality evidence shows chronic migraine patients experience a reduction of approximately 1.9-3.1 headache days per month compared to placebo with the 12-week dosing schedule 1, 7
This treatment is only effective for chronic migraine (≥15 headache days per month) and is ineffective for episodic migraine (<15 headache days per month) 1, 8
Common Pitfalls to Avoid
Never use Botox for episodic migraine (fewer than 15 headache days per month)—it is ineffective and not recommended by guidelines 1, 8
Do not deviate from the PREEMPT protocol injection pattern, as this is the only evidence-based approach validated for chronic migraine 1
Avoid injecting closer than 1 cm above the central eyebrow and ensure lateral corrugator injections are at least 1 cm above the bony supraorbital ridge to reduce risk of eyelid ptosis 2
Monitor for medication overuse headache concurrently, limiting simple analgesics to fewer than 15 days per month and triptans to fewer than 10 days per month 1, 8