Botulinum toxin is a protein produced by the bacterium Clostridium botulinum. The substance can only be produced under exclusion of air (oxygen deprivation) and at higher pH. This means that under normal atmospheric oxygen content or in a acidic (sour) environment no botulinum toxin is produced. In addition, it is inactivated by high temperature (cooking).
In the body, botulinum toxin acts as a neurotoxin: it inhibits the signal transmission from the nerve to the target organs (muscles, sweat glands, etc.). Under normal conditions, upon arrival of the electrical signal to the nerve ending, the neurotransmitter acetylcholine is released from the nerve and activates the cells of the target organ. This release is blocked by botulinum toxin. The target organ will remain inactive (paralyzed). In high doses, botulinum toxin can lead to death due to paralysis of the respiratory muscles.
There are several known subtypes of botulinum toxin with varying molecular structure and different strength and mode of action. Type A and B are currently used in medicine.
For thereapeutic purposes, the substance is mainly employed in conditions characterized by hypertonic or excessively active muscles (blepharospasm, torticollis, strabism, spasticity in cerebral palsy or paraplegics, anal fissures, etc.) or overactive sweat glands. In cosmetic medicine, botulinum toxin is used to smooth facial wrinkles by paralyzing the muscles that cause wrinkles to appear (mimic muscles).
The nerve ending contains the neurotransmitter ACETYLCHOLINE, enclosed in small bubbles. On arrival of the electrical signal of the nerve, these tiny containers adhere to the membrane of the nerve and fuse with it, expelling acetylcholine (exocytosis). This enables this substance reaching and activating the sweat gland.
The toxin of the bacterium Clostridium botulinum is able to neutralize some proteins within the nerve terminal, thus blocking the exocytosis of acetylcholine. The nervous signal cannot reach the sweat gland and sweating is inhibited. Only after several months, the nerve endings regain the ability to release acetylcholine and sweating returns gradually again.
The therapy consists in the execution of multiple subdermal injections with minimal amounts of toxin in order to uniformly cover the surface affected by excessive sweating.
The inhibitory effect lasts for approx. 5-8 months, after which the sweating will recur at the beginning so slight, increasing very slowly. In many cases, even after a year is not reached the level of initial hyperhidrosis. Therefore, for the majority of patients simply an annual treatment be repeated typically preferably before the summer season. Unfortunately, a small percentage of the treated cases (ca. 5-10%) does not respond to such therapy, presumably due to the presence of high antibody titers against the toxin. In some cases of non-responders repetition of treatment with higher doses can achieve the desired effect.
- The major advantage of this method consists in the almost total absence of side effects, in particular of a significant compensatory sweating.
- Other possible side effects would still be of transitory nature.
- Outpatient procedure.
- high cost of the substance
- result is not definitive
- painful treatment ON hands and feet in the absence of adequate anesthesia
- transient weakness of the muscles of the hand, with repercussions on fine movements
- possible interference on the facial mimicry (paralysis of the facial muscles)
Botulinum toxin appears as a therapy of choice for the treatment of axillary hyperhidrosis in cases refractory to anti-perspirants.
For this type of hyperhidrosis there is a tendency today to avoid the surgical approach, if possible. The local subcutaneous removal of the sweat glands (aspiration curettage) is frequently followed by relapse, while total excision will inevitably produce aesthetically unsatisfactory scars. Sympathetic surgery is often followed by compensatory sweating on the trunk.
On the other hand, botulinum toxin does almost never produce side effects if correctly injected into the axillary sweat glands.
Botulinum toxin is not recommended for treatment of excessive handsweat because of a series of shortcomings.
Botulinum toxin is totally unsuitable and useless for the treatment of sweaty feet, since the substance is pressed away from the sole of the foot under load when standing and walking, and is therefore not available to the nerves and can not be absorbed by the nerve endings in sufficient quantity.