الفهرس 
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Abstract
Summary
owadays, the use of botulinum toxin type A to treat
facial rhytides represents the leading procedure in
aesthetic facial treatments. Botulinum toxin type A is a protein
complex that is derived from the bacterium Clostridium
botulinum. As such, it is a biological agent that is produced
commercially using different methods and processes.
There are currently three available preparations of botulinum
toxin type A (i.e. Onabotulinum toxin A, Abobotulinum toxin A,
and Incobotulinum toxin A), all of which are supplied as
lyophilized powder for reconstitution prior to injection.
Importantly, due to their biological nature, each preparation has
different properties; the trade names should not be used generically
to describe the toxin and dosing recommendations for each product
as they are not interchangeable with other botulinum toxin type A
preparations. This means that the number of units recommended
for treatment is specific for each of these botulinum toxin type A
preparations.
Throughout the past years, few studies have been
dedicated to figure out an appropriate dosage conversion ratio
to use when switching patients from one preparation to another,
especially between the two most widely used botulinum toxin A
preparations (i.e. Onabotulinum toxin A and Abobotulinum
toxin A). Furthermore, comparing the clinical efficacy of these
two products at different dose equivalences would help to
determine which product is more beneficial to the patients
regarding the cost.
Although there has historically been considerable debate
concerning the dose equivalence that should be used in clinical
practice evidence recently showed that the ABO: ONA
equivalence ratio is lower than previously thought; the use of
high dose conversion ratios, as recommended in the older
literature, is no longer justified.
In this single-blinded, randomized, split-face study we
aimed to compare the clinical efficacy of the two botulinum
toxin A preparations (i.e. Onabotulinum toxin A [ONA] and
Abobotulinum toxin A [ABO]) at two different dosing ratios of
ABO: ONA; 2.5: 1.0 U and 3.0: 1.0 U in the treatment of the
forehead horizontal lines and the crow’s feet wrinkles. The end
points were the time to improvement, duration of improvement,
degree of improvement, patient satisfaction and complications.
Being a split-face study allowed us to eliminate all internal and
external variables that could affect the development and
severity of wrinkles, hence affect the response to treatment.
Forty patients (10 males and 30 females) were enrolled in
this study. All patients had moderate-to-very severe forehead
and periorbital wrinkles according to the Merz photonumerical
scales and none of them have ever received any botulinum toxin
A treatments. Patients were assigned equally on random basis
into two groups (i.e. Group A and B). Group A patients were
subjected to a dose conversion ratio of ABO: ONA; 2.5: 1.0U,
while group B patients received treatments at a dose
equivalence of ABO: ONA; 3.0: 1.0U.
A fixed total dose of Onabotulinum toxin A was given to
all patients among the two groups (i.e. 6 units per treated region
divided on 3 injection points). On the other hand, the total dose
of Abobotulinum toxin A was determined according to the dose
conversion ratio of each group. Hence, Group A patients
received a total dose of 15 units of Abobotulinum toxin A per
each treated region divided on 3 injection points, while group B
patients received 18 units of Abobotulinum toxin A per each
treated region divided on 3 injection points.
Digital photographs of patients, both at rest and at
maximum muscle contraction, were taken before treatment
session (i.e. baseline photos) and at days 7, 30, 120 postinjection.
Photograding was performed by consensus between
two dermatologists using the Merz photonumerical scales.
Our results, regarding the crow’s feet region, revealed
that at a dose conversion ratio of ABO: ONA; 2.5: 1.0U (i.e.
Group A) Abobotulinum toxin A had significantly earlier onset
and longer duration of action on dynamic posture, while no
significant difference in the onset or duration of action was
detected on static posture. On the other hand, raising the total
dose of Abobotulinum toxin A to 18 units per treated region in
group B (i.e. Dose equivalence of ABO: ONA; 3.0: 1.0U)
resulted in significantly more prominent dominance of
Abobotulinum toxin A in which it had an earlier onset and
longer duration of action on both static and dynamic postures.
Regarding the degree of improvement of the crow’s feet
wrinkles among both groups, results either showed no
significant difference between both preparations or revealed a
significantly better improvement in the Abobotulinum toxin A
treated side. In general, results of the crow’s feet region in both
groups matches most of the recently published studies which
suggest that a lower dose conversion ratio such as ABO: ONA;
2.0: 1.0U may be more appropriate to elicit equal potency
between the 2 preparations.
In the forehead region, at a dose equivalence of ABO:
ONA; 2.5: 1.0U (i.e. Group A), Onabotulinum toxin A had the
upper hand throughout all the study parameters except for the
time to improvement on static posture where no significant
difference was detected between both sides. On the other hand,
at a dose equivalence of ABO: ONA; 3.0: 1.0U (i.e. Group B),
no significant difference in the time to improvement, on both
static and dynamic postures, was detected between both sides.
Moreover, the duration of action on static posture in the same
group showed no significant difference between both sides.
Regarding the degree of improvement of the forehead
horizontal lines in group B, Onabotulinum toxin A had
significantly better efficacy throughout most of the follow-up
sessions, on both static and dynamic postures, except for the 3rd
follow-up session on static posture and the 2nd follow-up
session on dynamic posture where no significant difference was
found between both sides at these sessions. It was clear that
raising the total dose of Abobotulinum toxin A in group B to
18U per each injected region resulted in a less superior effect of
Onabotulinum toxin A than Abobotulinum toxin A in the
forehead region in group B than that found in group A. In
general, our results regarding the forehead region in both
groups, unlike those of the crow’s feet region, are not in
agreement with most of the recently published studies.
We relied in our explanations for the differences between
the results of the crow’s feet region and those in the forehead
region on two main factors. First was the total doses of
Abobotulinum toxin A we used in our study (i.e. 15U for each
treated region in group A, and 18U for each treated region in
group B) which were much smaller than the doses described in
the recently published studies. Moreover, our total doses of
Abobotulinum toxin A appear to be in the lower margin of the
recommended total dose range that has been reported in the
international consensus recommendations on the aesthetic
usage of Abobotulinum toxin A in upper facial wrinkles (i.e.
10-30U per side for the forehead horizontal lines, and 15-30U
per side for the crow’s feet wrinkles). These small total doses
we used may have been sufficient enough to produce a
significant effect in the smaller orbicularis oculi muscle (i.e.
Crow’s feet wrinkles), but not in the larger frontalis muscle (i.e.
Forehead horizontal lines).
The second factor is the more concentrated dilutions of
Abobotulinum toxin A that we used in our study (i.e. 250 U/ml
for group A and approximately 167 U/ml for group B) as
compared to those being described in the recently published
studies. This explanation depends on the theory postulated by
Hauser et al. (2012), which states that more concentrated
solutions would reduce the reliability in delivering a specific
unit dose, and more diluted concentrations are preferable to
increase the spread of the toxin, hence increase the field of its
effect. Thus, we suggest that the more concentrated dilutions
we administered to our patients may have reduced the ability of
Abobotulinum toxin A to spread and produce a potent effect in
a relatively larger muscle such as the frontalis in comparison to
the smaller lateral portion of the orbicularis oculi.
Analysis of the patient satisfaction ratings reported by
our participants was in alignment with our results. Patients were
generally more satisfied with the Abobotulinum toxin A treated
side of the crow’s feet region in both groups. On the other hand,
patients were more satisfied with the Onabotulinum toxin A
treated side of the forehead in group A and no significant
difference regarding patients satisfaction was detected between
both sides of the forehead in group B.
No serious side effects were reported and both
preparations were found to be safe and effective in treating the
forehead horizontal lines and the crow’s feet wrinkles.
Regarding the crow’s feet region, we recommend that a
lower conversion ratio, for example, ABO: ONA; 2.0: 1.0U
should be tried. However, regarding the forehead horizontal
lines, our study should be repeated with the same dosing ratios
using a larger total dose of Abobotulinum toxin A. In addition,
we suggest that using constant fixed dilutions and isovolumetric
injections of both products would help to obtain more eloquent
results. Furthermore, a well equipped photography lab and the
use of more objective methods of assessment (e.g.
Electromyography for measuring a specific muscle action
potential) would increase the accuracy of comparison.