Pharmaceutical products based on botulinum toxin, which are used in a range of conditions from facial wrinkles to muscle spasms such as cervical dystonia, could find a new application in the prevention of scar formation after trauma.

Researchers at the Mayo Clinic in the USA have discovered that injecting the agent into forehead wounds during the early phase of healing inhibits the formation of scar tissue and improves the eventual appearance of wounds after they have healed.

If validated in further studies, the approach would represent the first medication to minimise scarring, and the team is now planning a Phase III evaluation of the approach to determine the best dosage and look at the potential of the approach in different wound types.

The researchers believe the technique could be particularly valuable for people suffering facial wounds, and for those who are already scarred. In this case, the scar tissue could be removed surgically, and botulinum toxin could be injected into the surgical lesion to encourage it to heal in a more cosmetically-appealing way. It could also help avoid subsequent cosmetic operations to improve the appearance of scars in some patients.

The team, led by Holger Gassner who is now a fellow in facial plastic surgery at the University of Washington in Seattle, speculate that the approach works because it prevents muscular movement wrinkling the wound site, providing a flat surface for healing during the first two to three months after the wound occurs.

Muscles may repeatedly distort wounds in the healing phase, which can result in inflammation that produces a thicker or wider scar, according to the researchers.

The botulinum toxin used in the experiments – Allergan’s Botox (botulinum toxin type A) – is the market leader in the category and is expected to be banging on the door of blockbuster status this year with sales of $900-$950 million, split roughly 57% to 43% for therapeutic versus cosmetic uses.

In the trial, 31 patients with forehead wounds from trauma such as auto accidents or from surgery were randomly assigned to receive injections with either Botox or saline control. Their wounds were photographed at the time of the initial treatment and injection and again six months after initial treatment. Two experienced facial plastic surgeons rated the wounds' appearance, and the researchers averaged the ratings to give a final scar appearance score for each patient's wound.

They found that the facial plastic surgeons rated the cosmetic results of the wounds injected with botulinum toxin more favourably than the wounds injected with saline. Median scores for wounds injected with botulinum toxin were 8.9 out of 10, versus a median score of 7.1 for those injected with saline, which was a significant difference.

The findings are published in the August issue of Mayo Clinic Proceedings.