Research question:
Dose the use of oral zinc supplement improve the effects of botulinum toxins injection in
patients with myofascial pain dysfunction syndrome?
Statement of the problem:
MPDS Patients treated with botulinum toxin A injection usually suffers from return of the
symptoms which requires successive injections almost every (3-4M)
Rationale for conducting the research:
The concept of adding the zinc supplementation prior to BTXA injection is contributed to the
fact that botulinum toxin is a zinc-dependent metalloprotease; therefore, every botulinum
toxin molecule must be accompanied with a zinc molecule to effectively paralyze a muscle.
However, commercially available BTXA preparations exclude zinc from their preparations, and
BTX clinical efficiency and duration varies according to the zinc levels of the patient.
Although the BTX effect could remain for several months, its zinc-dependent proteolytic
activity befalls within hours of administration before the toxins are degraded in the
tissues.
Therefore, for achieving better results from BTX, the recipients should have adequate zinc
levels at the time of administration. Therefore, oral zinc supplement intake prior to BTXA
injection may enhance its clinical efficiency and duration.
botulinum neurotoxins are the most potent toxins known. They bind to nerve cells, penetrate
the cytosol and block neurotransmitter release. Comparison of their predicted amino acid
sequences reveals a highly conserved segment that contains the HExxH zinc binding motif of
metalloendo peptidases. The metal content of tetanus toxin was then measured and it was found
that one atom of zinc is bound to the light chain of tetanus toxin. Zinc could be reversibly
removed by incubation with heavy metal chelators. Zn2+ is coordinated by two histidines with
no involvement in cysteines, suggesting that it plays a catalytic rather than a structural
role.
Bound Zn + was found to be essential for the tetanus toxin inhibition of neurotransmitter
release in Aplysia neurons injected with the light chain. The intracellular activity of the
toxin was blocked by phosphoramidon, a very specific inhibitor of zinc endopeptidases.
Purified preparations of light chain showed a highly specific proteolytic activity against
synaptobrevin, an integral membrane protein of small synaptic vesicles. The present findings
indicate that tetanus toxin, and possibly also the botulinum neurotoxins, are
metalloproteases and that they block neurotransmitter release via this protease activity. So
The use of zinc supplementation prior to BTXA injection has been suggested by several
previous studies to prolong its duration of action as well as improve its efficacy