Units and Duration

Counting the dose

How many units go into a chewing muscle, and how long do they hold?

The short answer

Rewind plans the chewing muscle as one of two published unit plans, fifty units or one hundred, and states that the amount is matched to the individual structure of the patient. Duration published by the clinic for its toxin work is three to six months. A unit is a measure of biological potency defined separately for each preparation, so a number on its own describes very little until you also know which muscle received it.

Source: the clinic's Korean treatment page for this injection and its own rate list, where the two plans appear as separate items.

People arrive with a number in mind because a number travels well on social media. What the examination produces is a different thing: a muscle that has been felt at rest and under load, matched to the smaller of the two plans wherever that will do the work. The wider area menu sits on the botulinum toxin page.

From injection to wear-off

How is the number of units set, and what governs how long it lasts?

Three things decide the answer: the size of the muscle, the preparation being used, and what your own muscle did the last time it was treated. Only the first is visible at a first appointment.

01Unit

A unit is potency, and potency is defined per preparation

Units are assigned by biological assay for each type A preparation, and equivalence between preparations is something trials are designed to establish, never something to be assumed. Comparing a unit count quoted in one country with a unit count quoted in another tells you less than it appears to.

02Choose

Muscle size, clench strength and history select the plan

The surgeon palpates the muscle at rest and while you bite, compares the two sides, and looks at what the face needs to keep. Rewind's own statement is that the dose follows individual structure; the practical consequence is that a returning patient and a first-timer with identical faces can be given different plans.

03Shrink

Weakness comes first, thinning comes second

A prospective study that followed injected chewing muscles with ultrasound and electromyography recorded reduced electrical activity early and measurable thinning of the muscle over the months that followed. That sequence is why the mirror disappoints at week one and rewards patience at week six.

04Repeat

Whether later sessions need fewer units is answered by your record

Some patients find the interval stretching after two or three rounds as the muscle stays smaller between sessions; others hold to the same schedule for years. The clinic publishes no automatic reduction rule, so the second plan is written from the units used, the points chosen and your own report of when movement came back.

Published rates

What each chewing-muscle plan is listed at

Both plans appear on the clinic's published list as separate items, and an expression area treated at the same appointment is charged as its own line again.

Listed rates carry value-added tax separately; any anaesthetic fee is already inside the figure shown. Re-treatment later in the year is charged at the same published rate for whichever plan is chosen then.

The wear-off curve

What does the first month after a jaw dose feel like?

Rewind's written instructions for this injection are brief, and they concentrate on the first couple of days for a mechanical reason: product that is pushed around before it binds does not stay where it was placed.

Reported adverse effects from dosing this muscle include bruising and tenderness at the entry points, headache, chewing fatigue, asymmetry between the sides, and a temporary change in the smile where product reaches neighbouring muscles. Systematic review of aesthetic toxin use describes these events as generally transient; that is a reason to report one early, while the next plan can still be written around it.