What is the recommended dosage and administration of Botulinum toxin type A (Botox) for cosmetic improvement in a typical adult patient for the upper lip, Depressor Anguli Oris (DAO), and mentalis muscles?

Botulinum Toxin Dosing for Upper Lip, DAO, and Mentalis

For cosmetic treatment of the upper lip, DAO (Depressor Anguli Oris), and mentalis muscles in adults, inject 2-4 units per site in the DAO bilaterally (total 4-8 units), 2-4 units in the mentalis muscle, and 1-2 units per injection point in the upper lip perioral area, using a dilution of 4 units per 0.1 mL. 1

Anatomical Considerations and Injection Technique

DAO (Depressor Anguli Oris)

• The DAO pulls down the corners of the mouth, creating a sad or aged appearance 2
• Inject 2-4 units per side, approximately 1 cm lateral to the oral commissure and just above the inferior border of the mandible 1
• This muscle is now routinely treated and helps improve overall facial appearance 2
• Proper placement prevents diffusion into adjacent muscles that could cause asymmetry 1

Mentalis Muscle

• The mentalis creates a dimpled or "pebbled" chin appearance when contracted 1
• Inject 2-4 units total into the central mentalis muscle, typically as a single midline injection or two paramedian injections 1
• The injection should be placed in the lower third of the chin to avoid affecting the lower lip depressors 1

Upper Lip (Perioral Area)

• The orbicularis oris creates vertical lip lines and can cause a gummy smile 2, 1
• Inject 1-2 units per point, typically 2-4 injection points total around the upper lip, placed just above the vermillion border 1
• Use extreme caution with perioral injections as excessive dosing can impair lip function, speech, and drinking 1
• This is an advanced treatment area requiring precise technique to avoid complications 2

Reconstitution Protocol

• Reconstitute 100 units with 2.5 mL of preservative-free 0.9% sodium chloride to achieve 4 units per 0.1 mL 3
• Inject diluent slowly into the vial to avoid foaming, then rotate gently without vigorous shaking 3
• Use reconstituted solution within 24 hours when stored at 2-8°C 3

Critical Safety Considerations

Patient Selection

• Contraindications include hypersensitivity to botulinum toxin, neuromuscular disorders (myasthenia gravis), keloidal scarring, and body dysmorphic disorder 4, 5
• Younger, toxin-naïve patients typically require lower doses and are more concerned about looking frozen or unnatural 6

Common Pitfalls in Lower Face Treatment

• The lower face requires significantly more precision than upper face treatments due to functional implications 1
• Excessive DAO treatment can cause asymmetric smile or difficulty with oral competence 1
• Over-treatment of the mentalis can cause difficulty with lower lip eversion 1
• Perioral injections placed too deep or with excessive dosing can impair essential functions like drinking through a straw or pursing lips 1

Expected Timeline and Retreatment

• Effects develop over 24 hours to 2 weeks, with full results visible by 2 weeks 7, 5
• Duration of effect is 3-4 months for lower face areas 7, 5
• Dynamic wrinkles (visible during muscle contraction) respond better than static wrinkles (visible at rest) 5

Gender Considerations

• Men require more units of botulinum toxin than women due to greater muscle mass 2
• Consider increasing doses by 20-30% for male patients in these areas 2

Individualization Based on Age

• Younger adults (under 41 years) typically receive fewer total units and are primarily seeking wrinkle prevention rather than correction 6
• Start with lower doses in toxin-naïve patients and titrate upward at subsequent treatments based on response 6
• The optimal dose of cosmetic botulinum toxin for general facial treatments is cited as 20 units total, though lower face areas typically use less 7