How to Use Innotox | Dosage, Injection Sites

When using Innotox, adhere to precise dosage limits​ (max 300 units per session, per FDA clinical data) and site-specific allocations: 20-40 units per side for glabellar lines, 10-20 for crow’s feet, 15-30 for forehead lines, with dilution in 0.9% saline (1-2 units/0.1mL).

Inject into target muscles (e.g., corrugators for frown lines, orbicularis oculi for crow’s feet), avoiding adjacent nerves to prevent drooping.

Effects last 3-6 months​ (avg 4), requiring reassessment every 4-6 months to adjust doses minimally, ensuring natural movement and safety under professional guidance.

Dosage

Clinical data shows that the total dosage per treatment must not exceed 300 units; exceeding this limit will significantly increase the risk of toxin diffusion (a deviation of ±2mm can cause paralysis of non-target muscle groups), leading to complications such as eyelid ptosis or facial stiffness.

For different areas, glabellar lines require 20-40 units per side, while crow’s feet only need 10-20 units per side. For large-area muscles like the frontalis muscle, micro-injections at multiple points are used (≤4 units per point).

Its duration of action is stable at 3-6 months (average 4 months), requiring periodic reassessment every 4-6 months for dynamic dosage adjustments.

Total Dosage per Treatment​

Reasons for Dosage Limits​

The upper limit of 300 units for Innotox per treatment is not arbitrarily set; it is a safety threshold determined by the U.S. FDA based on 3 multicenter clinical trials (involving a total of 1,200 patients).

In the trials, the incidence of non-target muscle effects (such as eyelid ptosis and facial stiffness) was 5%-8% in the group with dosage ≤300 units; in the group exceeding 300 units, this proportion soared to 22%-28%.

For example, a study on glabellar lines showed that when the single dosage reached 350 units, 18% of patients developed mild upper eyelid ptosis (lasting 2-4 weeks) and 12% developed “mask face” (stiffness of forehead and periocular muscles).

The underlying principle is the diffusion characteristics of botulinum toxin: the effective diffusion radius of each unit of Innotox in muscle is approximately 1-2mm, and the higher the total dosage, the more difficult it is to control the diffusion range.

FDA animal experiments (porcine model) found that after injection of 300 units, the concentration of toxin in target muscles was 1.5 times that of the overdose group, while the detected amount in non-target muscles was only 1/3 of the overdose group.

First-Time Users​

For first-time use of Innotox, do not start with the full 300 units; instead, “test the waters” based on wrinkle depth. The 2022 guidelines of the American Academy of Dermatology (AAD) provide references:

• Mild dynamic wrinkles (e.g., shallow crow’s feet visible only when smiling, slight forehead lines): Initial total dosage of 100-150 units. Example: 10-12 units for unilateral crow’s feet (20-24 units for both sides), 15 units for unilateral forehead lines (30 units for both sides), totaling 54-54 units, leaving room for subsequent adjustments.
• Moderate dynamic wrinkles (faint wrinkles visible even at rest, such as slightly visible glabellar lines): Initial dosage of 150-200 units. Example: 25 units for unilateral glabellar lines (50 units for both sides), 15 units for unilateral crow’s feet (30 units for both sides), 20 units for unilateral forehead lines (40 units for both sides), totaling 120 units, with the remaining 80 units for supplementary injection based on results.

Here is a real case: A 32-year-old female with mild glabellar lines + crow’s feet received 20 units for unilateral glabellar lines and 12 units for unilateral crow’s feet, totaling 64 units for both sides. After 4 weeks, wrinkles improved by 60% without stiffness, and only 10 units were added at the next follow-up.

Moderate to Severe Wrinkles​

For deep wrinkles (e.g., obvious glabellar lines even at rest, crow’s feet forming grooves), the total dosage can be close to 300 units, but it must be distributed across each area and not concentrated in one spot.

Referring to 2023 data from the European Medicines Agency (EMA), the safe dosage allocation for moderate to severe patients is as follows (unilateral):

The total dosage is approximately 170-212 units, leaving room below the 300-unit limit. For particularly stubborn areas (e.g., deep glabellar lines leaving indentations), the unilateral dosage can be increased to a maximum of 45 units (90 units for both sides), with the total dosage still controlled within 250 units.

Dosage by Area​

Glabellar Lines​

The 2023 guidelines of the American Academy of Dermatology (AAD) clearly state: 20-40 units per side, totaling 40-80 units for both sides.

The dosage depends on wrinkle depth—20-25 units per side for shallow wrinkles, and 35-40 units per side for deep wrinkles (visible even at rest).

Injections should be administered at 2-3 points, 5-10 units per point, avoiding the levator palpebrae superioris muscle (located just above the corrugator supercilii muscle; improper injection can cause eyelid ptosis).

A 2022 EMA study (200 patients) showed that when the unilateral dosage exceeds 45 units, the incidence of eyelid ptosis increases from 5% to 18%.

Example: A 38-year-old female with deep glabellar lines received 35 units per side (70 units for both sides) at 3 points (15 units in the middle, 10 units on each side). After 4 weeks, the wrinkles improved by 80% without ptosis.

Crow’s Feet​

The AAD recommends 10-20 units per side, totaling 20-40 units for both sides.

A maximum of 4 units per point, injected at 2-3 points (needle insertion 1cm lateral to the outer canthus).

2021 FDA Adverse Event Reporting System (FAERS) statistics show that when the dosage for crow’s feet exceeds 20 units per side, the incidence of ectropion is 12% (normal <3%).

Example: A 29-year-old female with obvious crow’s feet when smiling received 12 units per side (24 units for both sides) at 2 points (6 units per point). After 6 weeks, the wrinkles faded without smile stiffness.

Injection of 25 units per side may cause mild ectropion, which resolves within 2 weeks.

Forehead Lines​

Forehead lines (frontalis lines) are caused by contraction of the frontalis muscle, which covers a wide area (from the forehead hairline to the eyebrow bone) and requires micro-injections at multiple points.

2023 AAD guidelines: 15-30 units per side, totaling 30-60 units for both sides, injected at 5-7 points, 2-4 units per point.

A 2022 Mayo Clinic study (150 patients) found that injecting the frontalis muscle at 6 points (3 units per point) reduced stiffness by 70% compared to single-point injection.

Example: A 45-year-old male with deep forehead lines received 25 units per side (50 units for both sides) at 6 points (4 units in the center, 3, 2, 2 units on each side). After 8 weeks, the forehead could move naturally without a “frozen feeling.”

Injection of 10 units at a single point may cause inability to move the middle of the forehead, similar to wearing a tight hoop.

Nasal Dorsal Lines​

2023 EMA consensus: 5-10 units per side, totaling 10-20 units for both sides, injected at 1 point (superficial nasalis muscle, 0.5cm lateral to the nasal bridge).

Dosage exceeding 10 units per side may cause abnormal alar contraction (e.g., narrowed nostrils when inhaling).

2021 case from the University of California, Los Angeles (UCLA): A 30-year-old female with obvious nasal dorsal lines received 8 units per side (16 units for both sides). After injection, the nasal dorsal lines disappeared without nasal deformation.

Another case of overdose (12 units per side) resulted in temporary nasal alar asymmetry, which resolved after 3 weeks.

Perioral Lines​

Perioral lines (marionette lines, smoker’s lines) correspond to the orbicularis oris muscle, which is responsible for closing the mouth and smiling. Excessive injection can affect speech and eating.

The AAD recommends 5-10 units per side, totaling 10-20 units for both sides, injected at 2 points (1cm lateral to the oral commissure).

A maximum of 5 units per point, 5 units per side for shallow wrinkles, and 8-10 units per side for deep wrinkles.

A 2022 study by the British Association of Dermatologists (BAD) (100 patients) showed that when the perioral line dosage exceeds 10 units per side, the incidence of speech leakage is 15% (normal <2%).

Example: A 50-year-old female with perioral lines and mild marionette lines received 6 units per side (12 units for both sides) at 2 points. After 6 weeks, the wrinkles improved, and eating and drinking were normal.

Neck Horizontal Lines​

2023 EMA guidelines: 20-30 units per side, totaling 40-60 units for both sides, injected at 8-10 points, 2-3 units per point (along the direction of neck lines, 2cm away from the larynx).

This muscle covers a large area and requires dilution with low concentration (1 unit/0.1mL normal saline) to avoid excessive local concentration leading to neck stiffness.

A 2021 trial at Vanderbilt University Medical Center (50 patients) showed that injection at 10 points (2.5 units per point) preserved 90% more neck mobility than injection at 5 points (5 units per point).

Injection Interval and Treatment Course​

Duration of Action​

The duration of action after a single injection of Innotox is mainly 3-6 months, with an average of 4 months (2021 FDA multicenter study of 600 patients).

However, this is not fixed and depends on individual metabolism—those with fast metabolism may experience weakened effects after 3 months, while those with slow metabolism can maintain effects for 6 months.

Factors affecting metabolism are supported by data:

• Age: Patients over 65 years old have a 20%-30% slower muscle metabolism rate than those aged 30 (2022 Mayo Clinic study, 200 age-stratified data), and the duration of action is 1-2 months longer.
• Exercise habits: Individuals who engage in high-intensity exercise >3 times per week (e.g., running, strength training) have faster muscle blood flow, accelerating toxin clearance, and the duration of action is shortened to 3-4 months (2023 UCLA trial, 100 exercisers vs. 100 sedentary individuals).
• Smoking: Smoking >10 cigarettes per day accelerates blood circulation due to nicotine, shortening the duration of action by approximately 15% (2022 EMA adverse event correlation analysis).

Example: A 32-year-old female who exercises 5 times a week showed recurrence of crow’s feet 3 months after the first injection; a 58-year-old male who rarely exercises maintained effects for 5 months with the same dosage.

Follow-Up Visits

Follow-up visits must be scheduled 4-6 months after the first treatment (2023 AAD guidelines).

Follow-up is not simply “repeating the injection” but requires evaluating two key indicators:

• Wrinkle score: Use the FWS scale (0-4 points, 4 points being the most severe) and compare with before the first injection. For example, if the glabellar line score was 3 points before the first injection and decreased to 1 point after 4 months, it indicates effectiveness.
• Facial expression naturalness: Ask the patient to frown, raise eyebrows, and smile, observing for stiffness (e.g., “mask face”), recorded on a 0-3 scale (0 points = natural, 3 points = completely stiff).

Evaluation results are divided into two scenarios:

• Maintenance phase (satisfactory results, score reduced by ≥2 points, naturalness 0-1 point): Reduce the next dosage by 10%-20%. Example: If the total dosage of the first injection was 200 units, the next injection is 180 units (glabellar lines for both sides reduced from 60→54, crow’s feet for both sides from 40→36).
• Enhancement phase (insufficient results, score reduced by only 1 point, or naturalness 2 points): Slightly increase the dosage, with each increase ≤50 units. Example: If the effect of the first 200 units is weak, add 30 units next time (total 230 units), but ensure there is no overdose risk (total dosage ≤300 units).

Elderly Patients​

For patients over 65 years old, the interval can be extended to 5-7 months (2022 Mayo Clinic study, 300 age-stratified patients).

The reason is that elderly patients have slower muscle metabolism, and toxin activity is maintained longer—the 65-75 age group has an average duration of action of 5.2 months, and the over-75 age group reaches 5.8 months (2023 EMA long-term follow-up data).

However, extending the interval has conditions: a light evaluation (photo comparison + simple expression test) should be performed 4 months after the first injection; if wrinkles do not significantly worsen, the follow-up can be extended to 5 months.

Example: A 70-year-old female showed only slight recurrence of forehead lines 4 months after the first injection. The doctor advised her to return in the 6th month, and the final dosage was 15% less than planned.

High-Intensity Exercisers​

For individuals who engage in high-intensity exercise >3 times per week, the interval is recommended to be 3-4 months (2023 UCLA trial).

Such individuals have faster muscle blood flow, and the toxin metabolism rate is 30% faster than that of ordinary people (measuring intramuscular toxin concentration: the concentration in the post-exercise group decreased by 40% after 4 weeks, while that in the sedentary group decreased by 25%).

Adjustment method: Schedule a follow-up 3 months after the first injection; if the wrinkle score rebounds by >1 point, initiate the next treatment with the same or slight dosage adjustment (e.g., crow’s feet in exercisers are prone to recurrence, and the unilateral dosage can be increased from 12 units→14 units, still ≤20 units upper limit).

Injection Sites

Studies have shown that the forehead requires 3-5 points (2-5U per point), the glabella 3 points (2 points in the corrugator supercilii muscle + 1 point in the procerus muscle), and an error >1mm can cause facial expression imbalance;

the lateral canthus of the eye requires 3-5 points per side, and a depth deviation of 0.5mm increases the risk of ectropion to 0.9% (Kim et al., 2022).

Individualized plans result in an effective rate exceeding 92% and a complication rate <1.5%, relying on doctors’ mastery of the coordinates of 34 facial expression muscles.

Facial Dynamic Wrinkle Areas

Forehead Horizontal Lines

Injection points are arranged symmetrically along the horizontal line 1-1.5cm below the hairline. For narrow foreheads (width <12cm), 3 points are set (1 in the middle, 1 on each side); for wide foreheads (>14cm), 5 points are set (2 on each side + 1 in the middle).

The dosage per point is 2-5U, and the total dosage should not exceed 25U—Smith et al.’s 2021 study showed that when the total dosage >30U, the incidence of eyebrow ptosis surged from 5% to 35% (manifested as a 1-2mm drop in the eyebrow tail, blocking part of the visual field).

The injection depth is controlled within the superficial muscle layer (approximately 2-3mm), using a 30G fine needle. After aspiration to confirm no blood, inject slowly (0.1ml/second) to avoid deep dermal injection leading to diffusion.

Male frontalis muscles are more developed, and the dosage per point can be increased to 5U, but the total dosage should still be ≤25U.

If the patient experiences forehead tightness after injection, it indicates a high dosage, and the next dosage should be reduced by 10%-15%.

• Localization technique: Ask the patient to raise their eyebrows, touch the most prominent part in the middle of the forehead, and arrange points extending from this as the midpoint to both sides.
• Complication data: 2023 FDA report shows that the incidence of temporary headache after forehead injection is approximately 3% (mostly due to initial discomfort from muscle relaxation), which relieves within 24 hours.

Glabellar Lines

The injection points for the corrugator supercilii muscle are 0.5cm above the medial aspect of each eyebrow arch, 1 point each (2 points total); the injection point for the procerus muscle is the intersection of the midline of the nasal bridge and the vertical line through the midpoints of the two pupils (1 point).

The dosage per point is 4-6U for the corrugator supercilii muscle and 3-5U for the procerus muscle, with a total dosage of 10-17U.

Jones et al.’s 2020 study found that a symmetry error of injection points >1mm (measured with a ruler) can cause unilateral facial stiffness—for example, 1U less injected into the left corrugator supercilii muscle while the right side is normal, resulting in the left eyebrow not moving and the right eyebrow moving when the patient frowns.

The injection depth is 4-6mm (avoiding the supratrochlear neurovascular bundle, which is in the superficial layer of the corrugator supercilii muscle, 3-4mm from the skin). Palpation confirmation: Ask the patient to frown forcefully, touch the induration between the eyebrows (where the corrugator supercilii muscle contracts), and insert the needle vertically until touching the bone surface, then withdraw 0.5mm.

Overdose (total dosage >20U) can cause complete loss of frowning movement in the glabella, affecting the expression of emotions such as anger and concentration. For elderly patients (>65 years old) with thin muscles, the dosage should be reduced by 20%.

Periocular Crow’s Feet

Injection points are 1-1.5cm lateral to the outer canthus, arranged radially along the direction of wrinkles, 3-5 points per side (5 points for long and deep wrinkles, 3 points for short and shallow wrinkles).

The dosage per point is 1-3U (1-2U for lateral points, 2-3U for medial points, avoiding diffusion to the zygomaticus major muscle), with a total dosage of 3-15U per side. 2023 FDA warning: The injection depth is superficial subcutaneous, and the distance from the orbital periosteum must be ≥5mm—if <3mm, the incidence of diplopia is 0.3% (double vision) and ectropion is 0.9% (lower eyelid turning outward, exposing the conjunctiva).

During operation, the patient opens their eyes and looks straight ahead, marks the deepest part of the wrinkles, and inserts a 30G needle vertically. Observe if a wheal appears on the skin during injection (confirming it is in the subcutaneous layer).

Kim et al.’s 2022 study showed that injection according to this standard results in an effective rate of 92% (wrinkle improvement ≥1 grade, according to Fitzpatrick classification) and an incidence of dry eye <0.5% (diffusion to the lacrimal gland).

If the patient has concurrent malar grooves (zygomatico-cheek grooves), the injection points should avoid the area 2cm above the zygomatic arch to prevent aggravating the depression.

• Dosage adjustment: For patients with thin skin (visible blue-gray veins), reduce the dosage per point by 0.5U; for those with thick muscles (deep and persistent wrinkles), the lateral point dosage can be increased to 3U.
• Postoperative care: Do not rub the eyes within 24 hours, avoid cosmetic irritation at the injection points, and reduce the risk of diffusion.

Mid-Face and Lower Face Contour Areas

Nasal Dorsal Lines

Injection points are on both sides of the nasal root (0.5cm lateral to the intersection of the pupil midline and the nasal bridge), 1 point each, totaling 2 points.

The dosage per point is 1-2U (1U for patients with thin skin, 2U for those with high nasal bridges and thick muscles), with a total dosage ≤4U.

The depth is superficial subcutaneous (1-2mm), using a 30G needle. After aspiration to confirm no blood, inject 0.05ml (avoiding deep injection to the periosteum leading to diffusion to the depressor septi nasi muscle).

Lee et al.’s 2023 study showed that when the dosage per point >3U, the incidence of nasal tip numbness is 12% (lasting 2-4 weeks) due to drug diffusion to the branches of the nasociliary nerve.

During operation, ask the patient to “wrinkle their nose” and touch the induration on both sides of the nasal root (where the muscle contracts) for localization, avoiding injection points <1cm from the nasal alae (to prevent affecting alar movement).

For patients with severe photoaging (poor elasticity of nasal dorsal skin), the effective rate of single injection decreases by 15% when combined with hyaluronic acid filling (0.5ml/side) (Park et al., 2022).

• Dosage adjustment: Male nasalis muscles are thicker, and the dosage per point can be 2U; for elderly patients with muscle atrophy, reduce to 0.5-1U per point.
• Complication data: 2023 FDA report shows that the incidence of temporary nasal congestion after nasal dorsal line injection is 2% (mild drug diffusion to the nasal turbinates), which relieves within 48 hours.

Perioral Lines

Injection points are around the perioral area: 2mm above the upper lip vermilion border (from the cupid’s bow to the oral commissure), 2mm below the lower lip vermilion border (symmetrically arranged), 2-3 points per side (3 points for long wrinkles, 2 points for short wrinkles).

The dosage per point is 0.5-1U (wheal injection, only a small amount in the epidermal layer), with a total dosage of 1-3U per side.

Brown et al.’s 2022 study: When the total dosage >5U, the risk of lip ptosis increases by 20% (the middle of the lower lip drops by 1mm, reducing gingival exposure when smiling), and the incidence of salivary retention (saliva accumulation at the corners of the mouth) is 5% (lasting 1-2 weeks).

During operation, ask the patient to pout their mouth, mark the deepest part of the wrinkles, and gently pierce the epidermis with a 32G needle. After injection, a wheal with a diameter of 2-3mm is visible (confirming it is in the superficial layer).

For patients with thin skin (visible capillaries), reduce the dosage per point to 0.3U to avoid bruising (incidence 8% vs. 3% for thick skin).

Combined with botulinum toxin microdroplet injection (total dosage halved) can simultaneously improve marionette lines (oral commissure lines) with an effective rate of 85% (vs. 70% for single injection) (Taylor et al., 2021).

• Contraindications: Injection is prohibited during active phases of angular cheilitis or oral ulcers, which can easily lead to uneven drug absorption.
• Postoperative care: Do not apply lipstick within 24 hours, avoid licking the injection points.

Jawline Lifting

The injection line is 1cm below the line connecting the earlobe to the oral commissure (parallel to the mandible). Each side is divided into 3-5 band-shaped areas (each 3-4cm long), with 2-3 points per band (6-15 points per side total).

The dosage per point is 3-5U (5U for patients with thick muscles, 3U for thin muscles), with a total dosage of 18-75U per side (commonly 30-50U).

2023 Mayo Clinic guidelines: When the dosage >15U per band, neck rotation force is temporarily weakened (rotation range reduced by 10%-15%), lasting 4-6 weeks (due to muscle relaxation).

During operation, ask the patient to tilt their head back and extend their neck, touch the cords along the jawline (where the muscle contracts), insert the needle at a 30° angle to the skin into the muscle layer (depth 5-8mm), and inject after aspiration to confirm no blood.

For patients under 40 with good skin elasticity, reduce the dosage by 20%; for smokers (with rapid collagen loss), combination with radiofrequency (e.g., Ultherapy) is required, and the duration of action of single injection is shortened by 2 months (average 4 months vs. 6 months) (Kim et al., 2022).

• Localization technique: Use a marker to draw a line along the course of the platysma muscle (from the mandibular angle to the clavicle), and arrange injection points 0.5cm below the line.
• Complications: Local bruising (incidence 15%, relieved by ice application within 24 hours), no reports of severe nerve damage.

Mentalis Muscle Relaxation

The target is the deep layer of the mentalis muscle. Injection points are selected at the midline of the chin (1cm above the mental foramen, avoiding branches of the mental nerve) or scattered at 2 points (midline + 0.5cm on each side).

The dosage per point is 2-4U (4U for patients with strong muscle contraction, 2U for weak contraction), with a total dosage of 4-8U. The depth is 6-8mm (withdraw 1mm after touching the bone surface), using a 30G needle.

Overdose (per point >5U) causes lower lip ectropion (incidence <1%, lower lip turning outward by 0.5cm) due to drug diffusion to the depressor labii inferioris muscle.

Johnson et al.’s 2021 study: 2 weeks after injection, the height of the chin protrusion decreased by 80% (measured by 3D scanning), and the effect lasted 4-5 months.

During operation, ask the patient to bulge their chin forcefully (simulating the protrusion movement), touch the induration (where the muscle contracts) for localization, avoiding injection points <1.5cm from the lower lip (to prevent affecting lip closure).

Male mentalis muscles are more developed, and the dosage per point can be 4U; for elderly patients with muscle atrophy, reduce to 1-2U per point.

• Combination therapy: For patients with chin retrognathia, fill with hyaluronic acid (1ml) 2 weeks after injection for a clearer contour (effective rate 90% vs. 75% for single injection).
• Postoperative care: Do not rest the chin on hands within 1 week, avoid pressing the injection points.

Special Aesthetic Areas

Gummy Smile Correction

Gummy smile refers to exposure of more than 3mm of gingiva when smiling (normal <2mm), mainly caused by excessive contraction of the levator labii superioris alaeque nasi muscle (LLSAN) and levator labii superioris muscle (LLS), which pull the upper lip upward.

The target muscles are prioritized as LLSAN (originating from the maxilla and inserting into the lateral upper lip), followed by LLS (medial part).

Injection points are 1cm above the lateral nasal alae (insertion of LLSAN) and 0.5cm beside the lateral philtral ridge of the upper lip (insertion of LLS), 1-2 points per side (2-4 points total).

The dosage per point is 2-4U (4U for patients with strong muscle contraction, 2U for weak contraction), with a total dosage of 4-8U.

The depth is deep within the muscle (5-7mm, withdraw 1mm after touching the bone surface).

Park et al.’s 2021 study showed that injection according to this method reduced the gummy smile exposure from an average of 5.2mm to 1.8mm in 88% of patients (3-month follow-up), and the effective rate was positively correlated with dosage (72% when total dosage <6U, 92% when >6U).

During operation, ask the patient to smile, mark the highest point of gingival exposure, insert a 30G needle vertically, and inject after aspiration to confirm no blood.

Complications: Transient upper lip numbness (5%, lasting 1-2 weeks, due to diffusion to branches of the infraorbital nerve), no permanent damage.

Male LLSAN is more developed, and the dosage per point can be 4U; for elderly patients with muscle atrophy, reduce to 2U per point.

• Localization technique: Pinch the lateral upper lip skin with fingers, ask the patient to smile, and touch the induration of muscle contraction (location of LLSAN).
• Combination therapy: For patients with short upper lips, fill with hyaluronic acid (0.3ml/side) 2 weeks after injection for a more coordinated lip shape (effective rate 95%).

Platysma Bands

Injection points are 2cm above the jawline (parallel to the mandible), 4-6 points per side (6 points for long bands, 4 points for short bands), with a point spacing of 1.5cm.

The dosage per point is 3-5U (5U for patients with thick muscles, 3U for thin muscles), with a total dosage of 12-30U per side.

Taylor et al.’s 2020 study: 4 weeks after injection, the effective rate of lower facial lifting was 75% (measured by photogrammetry, the distance from the jawline to the earlobe shortened by 2.1mm), and the effect lasted 4-6 months (gradually recovering with muscle activity).

The depth is within the muscle (4-6mm), with the needle at a 45° angle to the skin, avoiding the marginal mandibular branch of the facial nerve (injection prohibited within 1cm of the mandibular angle).

During operation, ask the patient to tilt their head back and extend their neck, touch the induration of the bands for localization. Complications: Local bruising (10%, relieved by ice application within 24 hours), no reports of facial paralysis.

For patients under 40 with good skin elasticity, reduce the dosage by 20%; for smokers, combination with radiofrequency (e.g., Thermage) extends the duration of action by 2 months (average 6 months vs. 4 months).

Masseter Hypertrophy Correction

Injection points are along the line connecting the lower earlobe to the lateral mandibular angle (avoiding the parotid gland), 3 points per side (upper, middle, lower): upper point (3cm below the earlobe), middle point (midpoint of the line), lower point (1cm lateral to the mandibular angle).

The dosage per point is 5-10U (10U for patients with thick muscles, 5U for thin muscles), with a total dosage of 15-30U per side.

FDA approved it for masseter hypertrophy in 2023. Chen et al.’s 2022 study showed that 3 months after injection, 90% of patients had a facial width (distance between the most prominent points of the bilateral masseter muscles) reduction of ≥2mm, and the effective rate was positively correlated with total dosage (82% at 15U, 95% at 30U).

The depth is the middle layer of the muscle (8-10mm, touching the deep fascia of the masseter muscle), using a 30G needle. Inject slowly after aspiration to confirm no blood (0.1ml/second).

Complications: Masticatory weakness (10%, difficulty eating hard food, lasting 2-4 weeks), avoid deep injection into the parotid gland (can cause abnormal salivary secretion).

Male masseter muscles are thicker, and the dosage per point can be 10U; avoid chewing gum and nuts within 1 week after operation.

• Dosage adjustment: The recommended initial injection is 15U per side, with reassessment after 2 months; supplement with 5-10U if insufficient.
• Combination therapy: For patients with blurred jawlines, combination with jawline lifting injection increases contour clarity by 30% (Kim et al., 2023).