Scientific skepticism and new discoveries: an analysis of a report of zinc/phytase supplementation and the efficacy of botulinum toxins in treating cosmetic facial rhytides, hemifacial spasm and benign essential blepharospasm

Botulinum Toxins and Zinc: From Theory to Practice-A Systematic Review

OBJECTIVE

The aims of this study were to determine whether zinc supplementation affects botulinum toxin's effect and longevity and to establish a transition from the molecular to the clinical aspect.

METHODS

We conducted a systematic review in which we included all published studies on PubMed and Embase using the combination of the following terms: "zinc" AND (botox OR botulinum OR onabotulinumtoxinA OR abobotulinumtoxinA OR incobotulinumtoxinA).

RESULTS

From the 260 yielded articles, 3 randomized control trials and 1 case report were retained. Three of them found a significant improvement with zinc supplementation in the toxin's effect and longevity. This was observed in neurological conditions and cosmetic uses.

CONCLUSIONS

Zinc supplementation could be an interesting asset in the potentialization of botulinum neurotoxin effect and longevity. Larger clinical trials and objective measurement tools should be used to further defining the role of zinc in maximizing botulinum neurotoxin effect.

Explanation of timing of botulinum neurotoxin effects, onset and duration, and clinical ways of influencing them

While the steps in the action of botulinum neurotoxin (BoNT) are well known, the factors underlying the timing of these steps are not fully understood. After toxin is injected into a muscle, it resides in the extracellular space and must be taken up into the nerve terminals. More toxin will be taken up if near the endplate. Toxin is distributed mainly by convection and there is likely little diffusion. Toxin that is not taken up will go into the general circulation where it may have a slight systemic effect. The uptake is activity and temperature dependent. Encouraging the unwanted muscle contractions after injection should be helpful. Cooling will decrease the uptake. The times for washout from the extracellular space and uptake of the toxin are not well established, but are likely measured in minutes. Toxin in the general circulation has a long half time. The time from injection to weakness is determined by how long it takes to get sufficient damage of the SNARE proteins to interfere with synaptic release. Toxins are zinc dependent proteases, and supplemental zinc may produce a greater effect. There will be weakness as long as there is residual toxin in the nerve ending.