Botulinum Toxin: Dosing Protocols

Prescribing Disclaimer#

Botulinum toxin type A is a prescription biological product that must be administered by qualified healthcare professionals. The dosing information presented here is derived from FDA-approved prescribing information and published clinical literature. This information is for educational purposes only and does not constitute prescribing guidance.

Units of botulinum toxin are NOT interchangeable between products. The potency units of onabotulinumtoxinA (Botox), abobotulinumtoxinA (Dysport), incobotulinumtoxinA (Xeomin), and prabotulinumtoxinA (Jeuveau) are determined by product-specific assays and are not equivalent across products. Doses described below refer to onabotulinumtoxinA unless otherwise specified.

Chronic Migraine (PREEMPT Protocol)#

The FDA-approved dosing protocol for chronic migraine prophylaxis is based on the PREEMPT clinical trial injection paradigm. The treatment involves 155 Units administered to 31 fixed injection sites across seven head and neck muscle groups, with an option for up to 40 additional Units at up to 8 follow-the-pain sites, for a total maximum dose of 195 Units across 39 sites.

The seven fixed-site muscle groups and their standard doses are: corrugator muscles (10 Units total, 5 per side), procerus muscle (5 Units), frontalis muscles (20 Units total), temporalis muscles (40 Units total), occipitalis muscles (30 Units total), cervical paraspinal muscles (20 Units total), and trapezius muscles (30 Units total). Each injection delivers 5 Units in a volume of 0.1 mL.

Treatment cycles are repeated every 12 weeks. Clinical trial data demonstrated that treatment effects are progressive, with greater efficacy observed in the second and subsequent treatment cycles compared to the first. Most clinical guidelines recommend at least two to three treatment cycles before determining treatment response.

Cervical Dystonia#

Dosing for cervical dystonia is individualized based on the pattern and severity of muscle involvement. The recommended starting dose is typically 150 to 200 Units, with the total dose distributed across the affected muscles. Commonly injected muscles include the sternocleidomastoid, splenius capitis, trapezius, levator scapulae, and scalene muscles.

The maximum recommended dose per treatment session is 300 Units for onabotulinumtoxinA. Electromyographic (EMG) guidance is recommended for targeting deeper cervical muscles to improve accuracy and reduce the risk of dysphagia. Treatments are repeated approximately every 12 weeks, with dose adjustments based on clinical response and adverse effects.

Cosmetic Applications#

Glabellar Lines#

The approved dose for moderate to severe glabellar lines is 20 Units distributed across 5 injection sites: one injection in the procerus muscle and two injections in each corrugator supercilii muscle. Each injection delivers 4 Units in 0.1 mL. The effect typically becomes apparent within 24 to 72 hours, with maximal effect at 1 to 2 weeks.

Lateral Canthal Lines#

The approved dose for crow's feet is 24 Units total, with 12 Units per side distributed across 3 injection sites per side (4 Units each). The injections target the lateral orbicularis oculi muscle.

Forehead Lines#

When treating forehead lines, 20 Units are distributed across 5 injection sites in the frontalis muscle (4 Units each). Forehead line treatment is typically combined with glabellar line treatment to avoid brow ptosis from unopposed frontalis relaxation.

Spasticity#

Upper Limb Spasticity (Adults)#

Doses range from 75 to 400 Units per treatment session, distributed across the affected muscles. Common targets include biceps brachii, flexor digitorum superficialis, flexor digitorum profundus, flexor carpi ulnaris, flexor carpi radialis, and adductor pollicis. The specific dose per muscle depends on muscle size, degree of spasticity, and prior treatment response.

Lower Limb Spasticity (Adults)#

Doses range from 300 to 400 Units per treatment session for ankle and toe spasticity, distributed across gastrocnemius, soleus, tibialis posterior, flexor hallucis longus, and flexor digitorum longus as indicated.

Reconstitution and Preparation#

OnabotulinumtoxinA is supplied as a vacuum-dried powder in single-use vials containing 50, 100, or 200 Units. Reconstitution is performed by slowly injecting preservative-free 0.9% sodium chloride injection into the vial. The diluent volume determines the concentration and should be selected based on the intended injection volume per site.

Common reconstitution volumes for the 100-Unit vial include 1.0 mL (10 Units per 0.1 mL, used for spasticity), 2.0 mL (5 Units per 0.1 mL, used for chronic migraine), and 4.0 mL (2.5 Units per 0.1 mL, used for some cosmetic applications and when larger injection volumes are desired). The reconstituted solution should be clear, colorless, and free of particulate matter. It should be gently swirled to dissolve the powder rather than shaken, as vigorous agitation can denature the protein.

Storage and Handling#

Unopened vials should be stored refrigerated at 2 to 8 degrees Celsius. Some formulations may alternatively be stored frozen at or below -5 degrees Celsius. Reconstituted solution should be stored in a refrigerator and used within 24 hours. The product is light-sensitive and should be protected from direct sunlight or prolonged exposure to room light. The product should not be used after the expiration date printed on the vial. Given the potency of botulinum toxin, proper disposal procedures for unused product and injection materials must be followed in accordance with institutional biohazard protocols.

Injection Technique Considerations#

Needle gauge selection varies by indication: 30-gauge needles are typically used for cosmetic injections and chronic migraine, while 25- or 27-gauge needles may be preferred for deeper muscle injections in spasticity and dystonia. EMG-guided injection is recommended for deeper or harder-to-palpate muscles to improve targeting accuracy and reduce adverse effects. Aspiration before injection is recommended to avoid intravascular administration.

Related Reading#

• Botulinum Toxin overview and research guide
• Botulinum Toxin side effects profile
• Botulinum Toxin research evidence